Journal articles: 'Perovskites, photoluminescence spectroscopy'

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Rakshit, Soumyadipta, Alicia Maldonado Medina, Luis Lezama, Boiko Cohen, and Abderrazzak Douhal. "The Effects of Mono- and Bivalent Linear Alkyl Interlayer Spacers on the Photobehavior of Mn(II)-Based Perovskites." International Journal of Molecular Sciences 24, no. 4 (February 7, 2023): 3280. http://dx.doi.org/10.3390/ijms24043280.

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Mn(II)-based perovskite materials are being intensively explored for lighting applications; understanding the role of ligands regarding their photobehavior is fundamental for their development. Herein, we report on two Mn (II) bromide perovskites using monovalent (perovskite 1, P1) and bivalent (perovskite 2, P2) alkyl interlayer spacers. The perovskites were characterized with powder X-ray diffraction (PXRD), electron spin paramagnetic resonance (EPR), steady-state, and time-resolved emission spectroscopy. The EPR experiments suggest octahedral coordination in P1 and tetrahedral coordination for P2, while the PXRD results demonstrate the presence of a hydrated phase in P2 when exposed to ambient conditions. P1 exhibits an orange-red emission, while P2 shows a green photoluminescence, as a result of the different types of coordination of Mn(II) ions. Furthermore, the P2 photoluminescence quantum yield (26%) is significantly higher than that of P1 (3.6 %), which we explain in terms of different electron-phonon couplings and Mn-Mn interactions. The encapsulation of both perovskites into a PMMA film largely increases their stability against moisture, being more than 1000 h for P2. Upon increasing the temperature, the emission intensity of both perovskites decreases without a significant shift in the emission spectrum, which is explained in terms of an increase in the electron-phonon interactions. The photoluminescence decays fit two components in the microsecond regime—the shortest lifetime for hydrated phases and the longest one for non-hydrated phases. Our findings provide insights into the effects of linear mono- and bivalent organic interlayer spacer cations on the photophysics of these kinds of Mn (II)-based perovskites. The results will help in better designs of Mn(II)-perovskites, to increase their lighting performance.

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Dar, M. Ibrahim, Gwénolé Jacopin, Simone Meloni, Alessandro Mattoni, Neha Arora, Ariadni Boziki, Shaik Mohammed Zakeeruddin, Ursula Rothlisberger, and Michael Grätzel. "Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites." Science Advances 2, no. 10 (October 2016): e1601156. http://dx.doi.org/10.1126/sciadv.1601156.

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Emission characteristics of metal halide perovskites play a key role in the current widespread investigations into their potential uses in optoelectronics and photonics. However, a fundamental understanding of the molecular origin of the unusual blueshift of the bandgap and dual emission in perovskites is still lacking. In this direction, we investigated the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials, that is, CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3, which emerged from our thorough studies of the effects of temperature on their bandgap and emission decay dynamics using time-integrated and time-resolved photoluminescence spectroscopy. The low-temperature (<100 K) photoluminescence of CH3NH3PbI3and CH3NH3PbBr3reveals two distinct emission peaks, whereas that of CH(NH2)2PbBr3shows a single emission peak. Furthermore, irrespective of perovskite composition, the bandgap exhibits an unusual blueshift by raising the temperature from 15 to 300 K. Density functional theory and classical molecular dynamics simulations allow for assigning the additional photoluminescence peak to the presence of molecularly disordered orthorhombic domains and also rationalize that the unusual blueshift of the bandgap with increasing temperature is due to the stabilization of the valence band maximum. Our findings provide new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices.

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Miruschenko M. D., Timkina I. A., Nautran V. R., Margarian I. V., Grigoryev E. A., Cherevkov S. A., and Ushakova E. V. "Optical Properties of Lead-Free Cs-=SUB=-2-=/SUB=-AgInCl-=SUB=-6-=/SUB=- : Bi/SiO-=SUB=-2-=/SUB=- Nanocrystals with Double Perovskite Crystal Structure." Optics and Spectroscopy 130, no. 8 (2022): 1021. http://dx.doi.org/10.21883/eos.2022.08.54776.3748-22.

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The optical characteristics of lead-free nanocrystals with a crystal structure of the double perovskite type with the chemical composition Cs2AgInCl6, doped with bismuth and coated with silicon dioxide were studied, and the possibility of their further application was shown. The optical properties of the nanocrystals under study are analyzed by absorption and luminescence spectroscopy, including those with time resolution. Images were obtained using a scanning electron microscope. The influence of the amount of silicon dioxide precursor addition on the optical properties and morphology of lead-free nanocrystals was established. It is shown that the observed broad photoluminescence band is associated with the occurrence of self-trapped excitons in such nanocrystals. To demonstrate the possibility of practical application of these nanocrystals a light-emitting device based on them was developed and constructed. The light emitting device has a wide emission spectrum close to warm white light. Keywords: LEDs, lead-free perovskites, double perovskites, nanocrystals, photoluminescence.

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Valverde-Chávez, David A., Esteban Rojas-Gatjens, Jacob Williamson, Sarthak Jariwala, Yangwei Shi, Declan P. McCarthy, Stephen Barlow, Seth R. Marder, David S. Ginger, and Carlos Silva-Acuña. "Nonlinear photocarrier dynamics and the role of shallow traps in mixed-halide mixed-cation hybrid perovskites." Journal of Materials Chemistry C 9, no. 26 (2021): 8204–12. http://dx.doi.org/10.1039/d1tc01492g.

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We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy.

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Ruan, Shuai, Maciej-Adam Surmiak, Yinlan Ruan, David P. McMeekin, Heike Ebendorff-Heidepriem, Yi-Bing Cheng, Jianfeng Lu, and Christopher R. McNeill. "Light induced degradation in mixed-halide perovskites." Journal of Materials Chemistry C 7, no. 30 (2019): 9326–34. http://dx.doi.org/10.1039/c9tc02635e.

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Kumar, Saranya, and Malathi Murugesan. "Lead-Free and Stable Potassium Titanium Halide Perovskites: Synthesis, Characterization and Solar Cell Simulation." Energies 15, no. 19 (September 23, 2022): 6963. http://dx.doi.org/10.3390/en15196963.

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Titanium based double perovskites have shown good optical properties along with remarkable stability, making them promising lead-free perovskites for optoelectronic applications. In this work, Potassium Titanium Halide (K2TiBr6, K2TiI6 and K2TiI2Br4) double perovskites are synthesized for the first time. Surface topology and chemical composition are studied. Photoluminescence characterization shows a peak in the UV region. The perovskites exhibit quasi bandgap with K2TiI6 having 1.62 eV direct bandgap, conducive for single junction solar cell fabrication. K2TiBr6 and K2TiI2Br4 have bandgaps 2.14 eV and 2.44 eV, respectively, which is favorable for tandem solar cell application. The decomposition temperature of K2TiI6 is notable at 678 °C, bestowing it with stability in ambient atmosphere. Inherent to its optical properties, Solar Cell Capacitance Simulator-1D (SCAPS-1D) is used to simulate perovskite solar cell (PSC) with K2TiI6 as the absorber. Utilizing the absorption data from UV-Vis spectroscopy, these PSCs are designed to give maximum efficiency. Upon numerical optimization of perovskite layer thickness, we propose an efficient, practically realizable PSC with a power conversion efficiency of 4.382%. Besides, various electron and hole transport layers are investigated and the effect of their thickness on the PSC performance are studied.

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Liu, Li, Yao, He, Liu, Xu, Han, and Wang. "Synthesis, Structure and Photoluminescence Properties of 2D Organic–Inorganic Hybrid Perovskites." Applied Sciences 9, no. 23 (November 29, 2019): 5211. http://dx.doi.org/10.3390/app9235211.

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Two-dimensional (2D) layered hybrid organic–inorganic perovskites have potential applications in solar cells, electroluminescent devices and radiation detection because of their unique optoelectronic properties. In this paper, four 2D layered hybrid organic–inorganic halide perovskites of (C6H5CH2NH3)2PbCl4, (C6H5CH2NH3)2PbBr4, (C6H5CH2NH3)2PbI4 and (C4H9NH3)2PbBr4 were synthesized by solvent evaporation. Their crystal structure and surface morphology were studied. The effects of different halogens and organic amines on perovskites’ absorption spectra were investigated, and the photoluminescence (PL) properties were studied by femtosecond ultrafast spectroscopy. The experimental results show that the four perovskites are well crystallized and oriented. With the increase of halogen atom number (Cl, Br, I) in turn, the UV-Vis absorption spectra peaks of perovskites redshift due to the increasing of the layer spacing, but organic amines have little effect on the spectra of perovskites. The PL intensity increases with increasing laser power, but the lifetime decreases with increasing laser power, which is mainly due to the non-geminate recombination. This research is of great significance for realizing the spectral regulation of organic–inorganic hybrid perovskites and promoting their application in nano-photonics and optoelectronic devices.

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Ghosh, Supriya, Bapi Pradhan, Yiyue Zhang, Johan Hofkens, Khadga J. Karki, and Arnulf Materny. "Nature of the different emissive states and strong exciton–phonon couplings in quasi-two-dimensional perovskites derived from phase-modulated two-photon micro-photoluminescence spectroscopy." Physical Chemistry Chemical Physics 23, no. 6 (2021): 3983–92. http://dx.doi.org/10.1039/d0cp05538g.

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Sekerbayev, Kairolla, Yerzhan Taurbayev, Gauhar Mussabek, Saule Baktygerey, Nikolay S. Pokryshkin, Valery G. Yakunin, Zhandos Utegulov, and Victor Yu Timoshenko. "Size-Dependent Phonon-Assisted Anti-Stokes Photoluminescence in Nanocrystals of Organometal Perovskites." Nanomaterials 12, no. 18 (September 14, 2022): 3184. http://dx.doi.org/10.3390/nano12183184.

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Anti-Stokes photoluminescence (ASPL), which is an up-conversion phonon-assisted process of the radiative recombination of photoexcited charge carriers, was investigated in methylammonium lead bromide (MALB) perovskite nanocrystals (NCs) with mean sizes that varied from about 6 to 120 nm. The structure properties of the MALB NCs were investigated by means of the scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. ASPL spectra of MALB NCs were measured under near-resonant laser excitation with a photon energy of 2.33 eV and they were compared with the results of the photoluminescence (PL) measurements under non-resonant excitation at 3.06 eV to reveal a contribution of phonon-assisted processes in ASPL. MALB NCs with a mean size of about 6 nm were found to demonstrate the most efficient ASPL, which is explained by an enhanced contribution of the phonon absorption process during the photoexcitation of small NCs. The obtained results can be useful for the application of nanocrystalline organometal perovskites in optoelectronic and all-optical solid-state cooling devices.

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Wang, Xiaoting, Fangfang You, Jianping Huang, Yi Yao, and Faqiang Xu. "Effect of Carrier Gas Flow Rate on the Morphology and Luminescence Properties of CsPbBr3 Microcrystals." Crystals 12, no. 4 (March 31, 2022): 479. http://dx.doi.org/10.3390/cryst12040479.

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All-inorganic halide perovskites, especially lead perovskite microcrystals, have attracted more and more attention because of their excellent photoelectric properties and chemical stability. Herein, high quality CsPbBr3 microcrystals with three different stable morphologies, namely microplate, frustum of a square pyramid and pyramid, were synthesized by the chemical vapor deposition (CVD) method through altering the flow rate of a carrier gas and were comparatively studied in structure and optical property. The photoluminescence (PL) results showed that the CsPbBr3 microplate has the best luminescence property. The structural characterization results by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray rocking curves (XRC) and Raman revealed that the flow rate of the carrier gas could manipulate the morphology evolution of CsPbBr3 microcrystals and further impact their luminescence properties.

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Jiang, Yiqun, Beiye Li, Tianxiang Zhang, Yumeng Shi, and Qing‐Hua Xu. "Photoluminescence Mechanisms of All‐Inorganic Cesium Lead Bromide Perovskites Revealed by Single Particle Spectroscopy." ChemNanoMat 6, no. 3 (January 30, 2020): 327–35. http://dx.doi.org/10.1002/cnma.201900690.

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Kojić, Vedran, Mario Bohač, Arijeta Bafti, Luka Pavić, Krešimir Salamon, Tihana Čižmar, Davor Gracin, et al. "Formamidinium Lead Iodide Perovskite Films with Polyvinylpyrrolidone Additive for Active Layer in Perovskite Solar Cells, Enhanced Stability and Electrical Conductivity." Materials 14, no. 16 (August 16, 2021): 4594. http://dx.doi.org/10.3390/ma14164594.

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In this paper, we studied the influence of polyvinylpyrrolidone (PVP) as a stabilization additive on optical and electrical properties of perovskite formamidinium lead iodide (FAPI) polycrystalline thin films on ZnO nanorods (ZNR). FAPI (as an active layer) was deposited from a single solution on ZNR (low temperature processed electron transport layer) using a one-step method with the inclusion of an anti-solvent. The role of PVP in the formation of the active layer was investigated by scanning electron microscopy and contact angle measurements to observe the effect on morphology, while X-ray diffraction was used as a method to study the stability of the film in an ambient environment. The effect of the PVP additive on the optical and electrical properties of the perovskite thin films was studied via photoluminescence, UV-Vis measurements, and electrical impedance spectroscopy. We have demonstrated that PVP inclusion in solution-processed perovskite FAPI thin films prevents the degradation of the film in an ambient atmosphere after aging for 2 months. The inclusion of the PVP also improves the infiltration of FAPI perovskite into ZnO nanostructures, increases electrical conductivity and radiative recombination of the photo-generated charge carriers. These results show promising information for promoting PVP stabilized FAPI perovskites for the new generation of photovoltaic devices.

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Merdasa, Aboma, Marina Gerhard, Boris Louis, Jun Li, Alexander Dobrovolsky, Yuxi Tian, Johan Hofkens, Rafael Camacho, Eva Unger, and Ivan G. Scheblykin. "Non-radiative processes in metal halide perovskite semiconductors probed by photoluminescence microscopy." EPJ Web of Conferences 190 (2018): 02011. http://dx.doi.org/10.1051/epjconf/201819002011.

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Organo metal halide perovskites are solution processed semiconductors that recently attracted a great attention. They possess a rather “soft” and (photo) chemically active solid structure allowing for ion migration and other mass diffusion processes. This is a likely reason why non-radiative recombination centres in these materials are activated and deactivated on relatively slow time-scales. This dynamics reveals as photoluminescence (PL) fluctuations (blinking) of individual microcrystals and local areas of films and allows for application of a broad range of single molecule spectroscopy methods including optical super-resolution. Studying PL blinking resolves properties of individual non-radiative centres and helps to unravel their chemical nature.

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Kranthiraja, Kakaraparthi, Sujan Aryal, Mahdi Temsal, Mohin Sharma, and Anupama B. Kaul. "Optical Property and Stability Study of CH3(CH2)3NH3)2(CH3NH3)3Pb4I13 Ruddlesden Popper 2D Perovskites for Photoabsorbers and Solar Cells and Comparison with 3D MAPbI3." Solar 2, no. 4 (September 20, 2022): 385–400. http://dx.doi.org/10.3390/solar2040023.

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Three dimensional (3D) perovskite solar cells (PSCs) are a promising candidate for third-generation photovoltaics (PV) technology, which aims to produce efficient photon conversion devices to electricity using low-cost fabrication processes. Hybrid organic-inorganic perovskites for-lmed using low-cost solution processing are explored here, which have experienced a stupendous rise in power conversion efficiency (PCE) over the past decade and serve as a prime candidate for third-generation PV systems. While significant progress has been made, the inherent hygroscopic nature and stability issue of the 3D perovskites (3DPs) are an impediment to its commercialization. In this work, we have studied two-dimensional (2D) organometallic halide (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1) layered perovskites in the Ruddlesden Popper structure, represented as BA2MA3Pb4I13 for the n = 4 formulation, for both photoabsorbers in a two-terminal architecture and solar cells, given that these material are considered to be inherently more stable. In the two-terminal photo absorber devices, the photocurrent and responsivity were measured as a function of incoming laser wavelength, where the location of the peak current was correlated to the emission spectrum arising from the 2DP film using photoluminescence (PL) spectroscopy. The 2D (BA)2(MA)3Pb4I13 films were then integrated into an n-i-p solar cell architecture, and PV device figures of merit tabulated, while our 3D MAPbI3 served as the reference absorber material. A comparative study of the 3DP and 2DP film stability was also conducted, where freshly synthesized films were inspected on FTO substrates and compared to those exposed to elevated humidity levels, and material stability was gauged using various material characterization probes, such as PL and UV-Vis optical absorption spectroscopy, scanning electron microscopy and X-ray diffraction. While the PCE of the 3D-PSCs was higher than the 2D-PSCs, our results confirm the enhanced environmental stability of the 2DP absorber films compared to the 3DP absorbers, suggesting their promise to address the stability issue broadly encountered in 3D PSCs toward third-generation PV technology.

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Zhang, Wei-Feng, Hong-Mei Pan, Yue-Yu Ma, Dong-Yang Li, and Zhihong Jing. "One-dimensional corner-sharing perovskites: Syntheses, structural evolutions and tunable photoluminescence properties." Journal of Molecular Structure 1253 (April 2022): 132221. http://dx.doi.org/10.1016/j.molstruc.2021.132221.

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Cichocka, Nikola, Serhiy Kobyakov, Jaroslaw Kaszewski, Anna Reszka, Roman Minikayev, Kamil Sobczak, Emilia Choinska, and Agata Kaminska. "Optical and structural properties of europium doped Y–Al–O compounds grown by microwave driven hydrothermal technique." Nanotechnology 33, no. 3 (October 29, 2021): 035702. http://dx.doi.org/10.1088/1361-6528/ac2e74.

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Abstract Perovskites, garnets, monoclinic forms, and lately also oxyhydroxides doped with rare-earth ions have been drawn large attention due to their beneficial optical and photovoltaic properties. In this work, we have shown that several forms of crystals from Y–Al–O family can be synthesized using microwave driven hydrothermal technique using different pH and post-growth annealing at different temperatures. The structural and optical properties of these crystals were investigated as a function of hydrothermal crystallization conditions. For this purpose, x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, transmission electron microscopy, photoluminescence, and photoluminescence excitation studies were performed. All the structures have been doped with Eu3+ ions which are known as a local symmetry sensor because various symmetries generate different crystal fields and thus affect their luminescence spectra. The optical properties of the obtained nanoparticles in correlation with their structure and chemical composition are discussed.

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Jiang, Shaojie, Yanan Fang, Ruipeng Li, Timothy J. White, Zhongwu Wang, Tom Baikie, and Jiye Fang. "Pressure-Induced Phase Transitions and Bandgap-Tuning Effect of Methylammonium Lead Iodide Perovskite." MRS Advances 3, no. 32 (2018): 1825–30. http://dx.doi.org/10.1557/adv.2018.154.

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ABSTRACTPressure-induced crystallographic transitions and optical behavior of MAPbI3 (MA=methylammonium) were investigated using in-situ synchrotron X-ray diffraction and laser-excited photoluminescence spectroscopy. We observed that the tetragonal phase that presents under ambient pressure transformed to a ReO3-type cubic phase at 0.3 GPa, which further converted into a putative orthorhombic structure at 2.7 GPa. The sample was finally separated into crystalline and amorphous fractions beyond 4.7 GPa. During the decompression, the phase-mixed material restored the original structure in two distinct pathways depending on the peak pressures. Being monitored using a laser-excited photoluminescence technique under each applied pressure, it was determined that the bandgap reduced with an increase of the pressure till 0.3 GPa and then enlarged with an increase of the pressure up to 2.7 GPa. This work lays the foundation for understanding pressure-induced phase transitions and bandgap tuning of MAPbI3, enriching potentially the toolkit for engineering perovskites related photovoltaic devices.

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Borri, Claudia, Nicola Calisi, Emanuele Galvanetto, Naomi Falsini, Francesco Biccari, Anna Vinattieri, Giuseppe Cucinotta, and Stefano Caporali. "First Proof-of-Principle of Inorganic Lead Halide Perovskites Deposition by Magnetron-Sputtering." Nanomaterials 10, no. 1 (December 26, 2019): 60. http://dx.doi.org/10.3390/nano10010060.

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The present work reports the application of RF-magnetron sputtering technique to realize CsPbBr 3 70 nm thick films on glass substrate by means of a one-step procedure. The obtained films show highly uniform surface morphology and homogeneous thickness as evidenced by AFM and SEM investigations. XRD measurements demonstrate the presence of two phases: a dominant orthorhombic CsPbBr 3 and a subordinate CsPb 2 Br 5 . Finally, XPS data reveals surface bromine depletion respect to the stoichiometrical CsPbBr 3 composition, nevertheless photoluminescence spectroscopy results confirm the formation of a highly luminescent film. These preliminary results demonstrate that our approach could be of great relevance for easy fabrication of large area perovskite thin films. Future developments, based on this approach, may include the realization of multijunction solar cells and multicolor light emitting devices.

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Falsini, Naomi, Nicola Calisi, Giammarco Roini, Andrea Ristori, Francesco Biccari, Paolo Scardi, Chiara Barri, Monica Bollani, Stefano Caporali, and Anna Vinattieri. "Large-Area Nanocrystalline Caesium Lead Chloride Thin Films: A Focus on the Exciton Recombination Dynamics." Nanomaterials 11, no. 2 (February 9, 2021): 434. http://dx.doi.org/10.3390/nano11020434.

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Caesium lead halide perovskites were recently demonstrated to be a relevant class of semiconductors for photonics and optoelectronics. Unlike CsPbBr3 and CsPbI3, the realization of high-quality thin films of CsPbCl3, particularly interesting for highly efficient white LEDs when coupled to converting phosphors, is still a very demanding task. In this work we report the first successful deposition of nanocrystalline CsPbCl3 thin films (70–150 nm) by radio frequency magnetron sputtering on large-area substrates. We present a detailed investigation of the optical properties by high resolution photoluminescence (PL) spectroscopy, resolved in time and space in the range 10–300 K, providing quantitative information concerning carriers and excitons recombination dynamics. The PL is characterized by a limited inhomogeneous broadening (~15 meV at 10 K) and its origin is discussed from detailed analysis with investigations at the micro-scale. The samples, obtained without any post-growth treatment, show a homogeneous PL emission in spectrum and intensity on large sample areas (several cm2). Temperature dependent and time-resolved PL spectra elucidate the role of carrier trapping in determining the PL quenching up to room temperature. Our results open the route for the realization of large-area inorganic halide perovskite films for photonic and optoelectronic devices.

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Awino, Celline, Victor Odari, Thomas Dittrich, Pongthep Prajongtat, Thomas Sakwa, and Bernd Rech. "Investigation of Structural and Electronic Properties of CH3NH3PbI3 Stabilized by Varying Concentrations of Poly(Methyl Methacrylate) (PMMA)." Coatings 7, no. 8 (August 3, 2017): 115. http://dx.doi.org/10.3390/coatings7080115.

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Studies have shown that perovskites have a high potential of outdoing silicon based solar cells in terms of solar energy conversion, but their rate of degradation is also high. This study reports on improvement on the stability of CH3NH3PbI3 by passivating it with polymethylmethacrylate (PMMA). Structural and electronic properties of CH3NH3PbI3 stabilized by polymethylmethacrylate (PMMA) were investigated by varying concentrations of PMMA in the polymer solutions. Stability tests were performed over a period of time using modulated surface photovoltage (SPV) spectroscopy, X-ray diffraction (XRD), and photoluminescence (PL) measurements. The XRD patterns confirm the tetragonal structure of the deposited CH3NH3PbI3 for every concentration of PMMA. Furthermore, CH3NH3PbI3 coated with 40 mg/mL of PMMA did not show any impurity phase even after storage in air for 43 days. The Tauc gap (ETauc) determined on the basis of the in-phase SPV spectra was found in the range from 1.585 to 1.62 eV for the samples stored during initial days, but shifted towards lower energies as the storage time increased. This can be proposed to be due to different chemical reactions between CH3NH3PbI3/PMMA interfaces and air. PL intensity increased with increasing concentration of PMMA except for the perovskite coated with 40 mg/mL of PMMA. PL quenching in the perovskite coated with 40 mg/mL of PMMA can be interpreted as fast electron transfer towards the substrate in the sample. This study shows that, with an optimum concentration of PMMA coating on CH3NH3PbI3, the lifetime and hence stability on electrical and structural behavior of CH3NH3PbI3 is improved.

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Arrar, A., M. Benhaliliba, A. Boukhachem, U. Yahşi, C. Tav, A. Yumak, and M. Amlouk. "Optical and photoluminescence spectroscopy analysis and Doppler broadening annihilation radiation studies of perovskites based on La1-XNiXMnO2.75 thin layers." Optik 224 (December 2020): 165678. http://dx.doi.org/10.1016/j.ijleo.2020.165678.

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Kojima, Kazunobu, Shuhei Ichikawa, Osamu Maida, Kohei Shima, and Shigefusa Chichibu. "(Invited) Characterization of Semiconductor Crystals Based on Omnidirectional Photoluminescence (ODPL) Spectroscopy." ECS Meeting Abstracts MA2022-01, no. 31 (July 7, 2022): 1301. http://dx.doi.org/10.1149/ma2022-01311301mtgabs.

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The performance of optical devices based on nitride semiconductors operating in the ultraviolet and visible wavelength regimes has been remarkably improved. For example, high-efficiency blue InGaN light-emitting diodes (LEDs) with an external quantum efficiency (EQE) of over 80% was achieved [Y. Narukawa, M. Ichikawa1, D. Sanga, M. Sano, and T. Mukai, J. Phys. D: Appl. Phys. 43, 354002 (2010)], and green laser diodes (LDs) was realized [Y. Enya, Y. Yoshizumi, T. Kyono, K. Akita, M. Ueno, M. Adachi, T. Sumitomo, S. Tokuyama, T. Ikegami, K. Katayama and T. Nakamura, Appl. Phys. Express 2, 082101 (2009)]. Recently, deep-ultraviolet AlGaN LEDs and LDs have also become hot topics. The nitride semiconductors have been actively applied not only to optical applications but also to electronic devices such as high-voltage transistors and high-electron mobility transistors based on their high breakdown voltage and saturation electron velocity. The performance of these optical and electronic devices relies on the crystal growth technology, where quality of GaN freestanding substrate is one of the most important issues. In recent years, it has become common for the "high-quality" GaN freestanding crystals to have a threading dislocation (TD) density of 106 cm-2 or less. TD density of 106 cm-2 corresponds to an average distance between TDs of 10 μm, which means that the TDs are sparser than 1 μm, the order of the carrier diffusion length. In other words, the TDs are no longer dominant in recombination processes of minority carriers (although this is a rather broad argument). In this case, the recombination processes, especially nonradiative recombination process, are likely to be dominated by point defects and impurities rather than by the sparse TDs. In fact, a negative correlation between room-temperature (RT) photoluminescence (PL) lifetime for the near-band-edge (NBE) emission and the concentration of VGaVN (a divacancy consisting of Ga and N vacancies) has been pointed out by a combined study of time-resolved PL measurements, positron annihilation spectroscopy, and theoretical calculations [S. F. Chichibu, A. Uedono, K. Kojima, H. Ikeda, K. Fujito, S. Takashima, M. Edo, K. Ueno, and S. Ishibashi, J. Appl. Phys. 123, 161413 (2018)]. Since PL lifetime measured at RT indicates nonradiative recombination lifetime when the internal quantum efficiency (IQE) of the crystal is low, this negative correlation means that the lower concentration of VGaVN induces larger intensity of the NBE emission. Actually, we have observed PL lifetime exceeding 2 ns at RT in a GaN crystal grown by halide vapor phase epitaxy (HVPE) on m-plane GaN grown by the acidic ammonothermal method as a seed crystal [K. Kojima, Y. Tsukada, E. Furukawa, M. Saito, Y. Mikawa, S. Kubo, H. Ikeda, K. Fujito, A. Uedono, and S. F. Chichibu, Appl. Phys. Express 8, 095501 (2015)]. This is an extremely long value for a GaN crystal, which means that the nonradiative recombination lifetime is long, i.e., the IQE of the NBE emission is large. In this case, the validity of the approximation where the PL lifetime at RT is directly read into the nonradiative recombination lifetime becomes an issue. Therefore, in order to compare the quality of GaN freestanding crystals, it is important to measure the IQE as well as the PL lifetime. The IQE value for the NBE emission in semiconductor crystals is a quantity that represents the balance between radiative and nonradiative recombination processes and is directly related to the concentration of point defects and impurities that form deep levels. Therefore, the IQE can be used as an indicator of not only the energy-saving performance of optical devices but also the performance of GaN crystals as a substrate material in electronic devices. In this presentation, the characterization of semiconductors with direct bandgap by using omnidirectional photoluminescence (ODPL) spectroscopy, a technique that can determine the IQE from the EQE without the need for model calculations, will be reviewed. Using GaN, ZnO, and metal halide perovskites as examples, specific procedures and applications of IQE determination will be discussed. In particular, the ability to measure large sample crystals or wafers is one of the major features of the ODPL spectroscopy, and it is expected to be combined with mapping measurements of the entire surface of semiconductor wafers and various types of nonlinear and microscopic spectroscopy.

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Kausar, Samia, Ataf Ali Altaf, Muhammad Hamayun, Nasir Rasool, Mahwish Hadait, Arusa Akhtar, Shabbir Muhammad, Amin Badshah, Syed Adnan Ali Shah, and Zainul Amiruddin Zakaria. "i-Propylammonium Lead Chloride Based Perovskite Photocatalysts for Depolymerization of Lignin Under UV Light." Molecules 25, no. 15 (July 31, 2020): 3520. http://dx.doi.org/10.3390/molecules25153520.

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Lignin depolymerization for the purpose of synthesizing aromatic molecules is a growing focus of research to find alternative energy sources. In current studies, the photocatalytic depolymerization of lignin has been investigated by two new iso-propylamine-based lead chloride perovskite nanomaterials (SK9 and SK10), synthesized by the facile hydrothermal method. Characterization was done by Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), UV-Visible (UV-Vis), Photoluminescence (PL), and Fourier-Transform Infrared (FTIR) Spectroscopy and was used for the photocatalytic depolymerization of lignin under UV light. Lignin depolymerization was monitored by taking absorption spectra and catalytic paths studied by applying kinetic models. The %depolymerization was calculated for factors such as catalyst dose variation, initial concentration of lignin, and varying temperatures. Pseudo-second order was the best suited kinetic model, exhibiting a mechanism for lignin depolymerization that was chemically rate controlled. The activation energy (Ea) for the depolymerization reaction was found to be 15 kJ/mol, which is remarkably less than conventional depolymerization of the lignin, i.e., 59.75 kJ/mol, exhibiting significant catalytic efficiencies of synthesized perovskites. Products of lignin depolymerization obtained after photocatalytic activity at room temperature (20 °C) and at 90 °C were characterized by GC-MS analysis, indicating an increase in catalytic lignin depolymerization structural subunits into small monomeric functionalities at higher temperatures. Specifically, 2-methoxy-4-methylphenol (39%), benzene (17%), phenol (10%) and catechol (7%) were detected by GC-MS analysis of lignin depolymerization products.

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24

Liu, Ting, Chen Li, Beilei Yuan, Yang Chen, Haoming Wei, and Bingqiang Cao. "Dopant compensation in p-type doped MAPb₁₋_xCu_xI₃ alloyed perovskite crystals." Applied Physics Letters 121, no. 1 (July 4, 2022): 012102. http://dx.doi.org/10.1063/5.0095370.

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Tuning the optical and electrical properties of semiconductors by designed doping is the basis of most energy-related semiconductor optoelectronic devices. In this Letter, we report the dopant compensation effect of P-type doped MAPb1− x Cu xI3 alloyed perovskite crystals. MAPb1− xCu xI3 single crystals were prepared by the inverse temperature crystallization method using cupric chloride (CuCl2) as the doping source. By XRD, XPS, STEM, and photoluminescence (PL) spectra analyses, we demonstrate that the doped cupric (Cu2+) ions can partially substitute lead (Pb2+) ions and form Cu–Pb based crystal semiconductor alloys of MAPb1− xCu xI3 with tunable bandgap by controlling the Pb/Cu ratio. More detailed XPS analysis of the doped crystal shows that the Cu2+ ions in MAPb1− xCu xI3 are partially reduced by I− ions, and the coexistence of two valence states of Cu species (Cu2+ and Cu+) was observed in the doped crystals. Hall results of MAPb1− xCu xI3 semiconductors show that the presence of reduced Cu+ ions impels the change of conductive type from weak N-type to P-type obviously, while the resistivity of doped MAPb1− xCu xI3 increases significantly from 104 to 107 Ω cm. The defect-related optical fingerprints of cupric doped crystals were investigated in detail by temperature-dependent PL spectroscopy. The pristine MAPbI3 perovskite crystal exhibits intrinsic donor bound exciton (D0X) luminescence at low temperature (10 K), while the doped MAPb1− xCu xI3 perovskites exhibit donor-acceptor or bound exciton (A0X) peaks related to a Cu+ dopant in sequence with the increase in the Cu ion content. These results indicate that the doping of Cu2+/+ ions into the MAPb1− xCu xI3 crystal not only changes the semiconductor bandgap but also causes the dopant compensation.

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Ekanayaka, Thilini K., Dylan Richmond, Mason McCormick, Shashank R. Nandyala, Halle C. Helfrich, Alexander Sinitskii, Jon M. Pikal, Carolina C. Ilie, Peter A. Dowben, and Andrew J. Yost. "Surface Versus Bulk State Transitions in Inkjet-Printed All-Inorganic Perovskite Quantum Dot Films." Nanomaterials 12, no. 22 (November 10, 2022): 3956. http://dx.doi.org/10.3390/nano12223956.

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The anion exchange of the halides, Br and I, is demonstrated through the direct mixing of two pure perovskite quantum dot solutions, CsPbBr3 and CsPbI3, and is shown to be both facile and result in a completely alloyed single phase mixed halide perovskite. Anion exchange is also observed in an interlayer printing method utilizing the pure, unalloyed perovskite solutions and a commercial inkjet printer. The halide exchange was confirmed by optical absorption spectroscopy, photoluminescent spectroscopy, X-ray diffraction, and X-ray photoemission spectroscopy characterization and indicates that alloying is thermodynamically favorable, while the formation of a clustered alloy is not favored. Additionally, a surface-to-bulk photoemission core level transition is observed for the Cs 4d photoemission feature, which indicates that the electronic structure of the surface is different from the bulk. Time resolved photoluminescence spectroscopy indicates the presence of multiple excitonic decay features, which is argued to originate from states residing at surface and bulk environments.

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26

Sekerbayev, K. S., G. K. Mussabek, Ye Shabdan, and Ye T. Taurbayev. "Ligand Assisted Control of Photoluminescence in Organometal Perovskite Nanocrystals." Eurasian Chemico-Technological Journal 23, no. 2 (August 30, 2021): 89. http://dx.doi.org/10.18321/ectj1078.

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Organometal perovskite nanocrystals have shown remarkable properties not only in photovoltaics, but also in light-emitting devices. In this work colloidal nanocrystals of organometal perovskite CH3NH3PbBr3 (MAPBr) with effective visible photoluminescence were synthesized by the ligand assisted reprecipitation method. The studies were carried out by photoluminescence spectroscopy and optical transmission spectroscopy. Analysis of the photoluminescence and transmission spectra showed that by changing the concentration of the ligands oleylamine and octylamine, it is possible to control the size of nanocrystals and the photoluminescence wavelength due to the quantum confinement effect. It was shown that the increase in ligands concentration in MAPBr perovskite nanocrystals (NCs) solutions decreases the width of the peak which indicates a better quality of the obtained nanocrystals. An increase in the band gap indicates a decrease in the size of the nanocrystals. Replacing the ligands in the colloidal perovskite NCs solutions leads to shift of the photoluminescence peak from 456 to 535 nm.

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27

Dadı, Seyma, Yemliha Altıntas, Emre Beskazak, and Evren Mutlugun. "Plasmon Enhanced Emission of Perovskite Quantum Dot Films." MRS Advances 3, no. 14 (2018): 733–39. http://dx.doi.org/10.1557/adv.2018.6.

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ABSTRACTWe propose and demonstrate the photoluminescence enhancement of CsPbBr3 perovskite quantum dot films in the presence of Au nanoparticles. Embedded into a polymer matrix, Au nanoparticle- quantum dot film assemble prepared by an easy spin coating method enabled the photoluminescence enhancement of perovskite quantum dot films up to 78%. The properties of the synthesized perovskite QDs and gold nanoparticles have been analysed using high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X- ray spectroscopy, UV-Vis absorption spectrophotometer, steady state and time-resolved photoluminescence spectrometer.

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Wang, Jie, Yu-Qi Sun, and Dong Shi. "Fast electronic trapping and de-trapping by mid-gap states in CH₃NH₃PbCl₃ single crystal." Applied Physics Letters 122, no. 4 (January 23, 2023): 041101. http://dx.doi.org/10.1063/5.0130512.

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The assumed existence of mid-gap states and their roles acting as electronic traps in lead halide perovskites are under intensive discussion. Yet, knowledge about their physical characteristics remains limited due to the lack of directly accessed optical evidence. Here, we report direct access of spectroscopic responses by mid-gap states in one prototypical metal halide perovskite, CH3NH3PbCl3 single crystal. Mid-gap electronic trapping shown by sub-gap absorption and photoluminescence quenching is demonstrated. Quenching of the inter-band photoluminescence leads to instantaneous broadening in the energetic distributions of the mid-gap, making it hard to determine the energy of each individual mid-gap state. Therefore, the subsequent mid-gap luminescence following electronic de-trapping shows largely increased spectral linewidth and varied luminescence maxima energy. Time-resolved photoluminescence revealed the fast trapping and de-trapping kinetics by mid-gap states in the CH3NH3PbCl3 single crystal. By combining existing knowledge about mid-gap states in semiconductor crystals, we define a general on-lattice surface dangling bonds scenario serving as the creation of mid-gap states in the robust CH3NH3PbCl3 single crystal.

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Kumar, Ashish, S. S. Rawat, Sanjay Kumar Swami, Vidya Nand Singh, and Ritu Srivastava. "Benzoyl Halide as Alternative Precursor for Synthesis of Lead Free Double Perovskite Cs3Bi2Br9 Nanocrystals." Journal of Nanoscience and Nanotechnology 20, no. 6 (June 1, 2020): 3802–8. http://dx.doi.org/10.1166/jnn.2020.17495.

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Ternary bismuth halides are interesting functional materials closely related to Pb halide perovskite photovoltaic material, and are widely sought after due to reduced toxicity of Bi compared to Pb. There are several reports on synthesis of Cs3Bi2Br9 nanocrystals (NCs) due to its being relatively stable compared to lead perovskite. Cs3Bi2Br9 nanocrystals have been synthesised using benzoyl bromide as an precursor using hot injection process at two different temperatures of 120 °C and 160 °C. Samples have been characterized for its structural, optical, microstructural and luminescent properties using X-ray diffraction, (XRD) UV-Vis spectroscopy, high resolution transmission electron microscopy and photoluminescent spectroscopy. XRD showed formation of Cs3Bi2Br9 phase with mono-crystalline structure. UV-Vis showed two types of band gap in the visible region which shows that the material can be used for photovoltaic applications. HRTEM confined the particles to be composed of nanocrystals with ˜5 nm particles in the samples grown at 120 °C and it the particles joined together yield various structures composed of nanoparticles. The time resolved photoluminescence shows average life times of 3.067 ns and 4.761 ns for samples grown at two different temperatures. To the best of our knowledge, this is the first report where benzoyl halide has been used as alternative precursor for the synthesis of lead free double perovskite Cs3Bi2Br9 nanocrystals which have many applications.

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Du, Jiaren, and Dirk Poelman. "Facile Synthesis of Mn4+-Activated Double Perovskite Germanate Phosphors with Near-Infrared Persistent Luminescence." Nanomaterials 9, no. 12 (December 11, 2019): 1759. http://dx.doi.org/10.3390/nano9121759.

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Tetravalent manganese doped phosphors are emerging as a new class of efficient near-infrared emitters for applications in a variety of areas, such as bioimaging and night-vision surveillance. Novel double perovskite-type La2MgGeO6:Mn4+ phosphors were successfully prepared using a microwave-assisted energy-saving solid state method. This simple technique involving the use of a microwave susceptor allows for a reduction of the preparation time compared to a conventional solid state reaction. The samples were investigated using powder X-ray diffraction, scanning electron microscopy, as well as energy-dispersive X-ray spectroscopy mapping, photoluminescence excitation/emission spectroscopy, persistent luminescence decay and temperature-dependent photoluminescence analysis. Substitution between isovalent Mn4+ and Ge4+ can be achieved without additional charge compensators in this germanate-based phosphor, which provides strong emission in the near-infrared spectral region, assigned to the characteristic transitions of tetravalent manganese ions. Additionally, the double perovskite-type germanate phosphor exhibits excellent luminescence thermal stability. Moreover, the spectroscopic properties, excitation wavelength-dependent and temperature-dependent persistent luminescence were studied. A series of thermoluminescence measurements were presented trying to give clear information on the charging process, afterglow behavior and the nature of the traps responsible for the persistent luminescence. The present investigation expands the range of available promising near-infrared emitting persistent phosphors for medical imaging.

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Li, Bin, Guo-Feng Zhang, Rui-Yun Chen, Cheng-Bing Qin, Jian-Yong Hu, Lian-Tuan Xiao, and Suo-Tang Jia. "Research progress of single quantum-dot spectroscopy and exciton dynamics." Acta Physica Sinica 71, no. 6 (2022): 067802. http://dx.doi.org/10.7498/aps.71.20212050.

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Colloidal semiconductor quantum dots (QDs) have strong light absorption, continuously adjustable narrowband emission, and high photoluminescence quantum yields, thereby making them promising materials for light-emitting diodes, solar cells, detectors, and lasers. Single-QD photoluminescence spectroscopy can remove the ensemble average to reveal the structure information and exciton dynamics of QD materials at a single-particle level. The study of single-QD spectroscopy can provide guidelines for rationally designing the QDs and giving the mechanism basis for QD-based applications. We can also carry out the research of the interaction between light and single QDs on a nanoscale, and prepare QD-based single-photon sources and entangled photon sources. Here, we review the recent research progress of single-QD photoluminescence spectroscopy and exciton dynamics, mainly including photoluminescence blinking dynamics, and exciton and multi-exciton dynamics of single colloidal CdSe-based QDs and perovskite QDs. Finally, we briefly discuss the possible future development trends of single-QD spectroscopy and exciton dynamics.

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32

Deo, Meenal, Alexander Möllmann, Jinane Haddad, Feray Ünlü, Ashish Kulkarni, Maning Liu, Yasuhiro Tachibana, et al. "Tantalum Oxide as an Efficient Alternative Electron Transporting Layer for Perovskite Solar Cells." Nanomaterials 12, no. 5 (February 25, 2022): 780. http://dx.doi.org/10.3390/nano12050780.

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Electron transporting layers facilitating electron extraction and suppressing hole recombination at the cathode are crucial components in any thin-film solar cell geometry, including that of metal–halide perovskite solar cells. Amorphous tantalum oxide (Ta2O5) deposited by spin coating was explored as an electron transport material for perovskite solar cells, achieving power conversion efficiency (PCE) up to ~14%. Ultraviolet photoelectron spectroscopy (UPS) measurements revealed that the extraction of photogenerated electrons is facilitated due to proper alignment of bandgap energies. Steady-state photoluminescence spectroscopy (PL) verified efficient charge transport from perovskite absorber film to thin Ta2O5 layer. Our findings suggest that tantalum oxide as an n-type semiconductor with a calculated carrier density of ~7 × 1018/cm3 in amorphous Ta2O5 films, is a potentially competitive candidate for an electron transport material in perovskite solar cells.

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33

Zhou, Yu, Beilei Yuan, Haoming Wei, Fan Xu, Yujiao Li, Xin Chen, and Bingqiang Cao. "Stable CsPbX₃ mixed halide alloyed epitaxial films prepared by pulsed laser deposition." Applied Physics Letters 120, no. 11 (March 14, 2022): 112109. http://dx.doi.org/10.1063/5.0081955.

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The pulsed laser deposition (PLD) technique has been proved to be able to grow oxide thin films with high structural quality with precisely controlled composition and thickness to achieve designed optical and electronical properties established in alloyed semiconductors and heterostructures. In this Letter, inorganic halide perovskite CsPb(IxClyBr1−x−y)3 epitaxial alloyed films on (001)-SrTiO3(STO) substrates were grown by PLD. The film crystal quality, phase stability, and the epitaxial relationship between the film and substrate were characterized with a detailed x-ray diffraction technique like high-resolution reciprocal spatial mapping and ϕ-scan. In addition, the photocarrier dynamics of the alloyed epitaxial films were investigated by photophysics spectroscopy, including steady and femtosecond transient optical absorption spectroscopy and temperature-dependent and time-resolved photoluminescence spectroscopy. The bandgap of the CsPbX3 films was tuned from 1.75 to 2.98 eV by substituting X with I/Br/Cl and their mixture of different ratios. Free exciton emissions were observed at a low temperature photoluminescence spectrum (PL, 10 K), which confirmed the high crystal and optical quality of the epitaxial perovskite alloyed films except the CsPbI3 film. The femtosecond transient absorption spectra also showed that such perovskite films are of very low concentration of exciton trap states. These results indicated that PLD is a powerful technology for growing high quality inorganic halide perovskite films with a tunable bandgap covering the full visible light range, which provided more options for CsPbX3 based panchromatic LED and other optoelectronic devices.

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Asai, Takaho, Seigo Ito, and Takayuki Makino. "Contactless Determination of Optimal Chloride Concentration for Power Conversion Efficiency in CH3NH3Pb(Cl,I)3 Using Photoluminescence Spectroscopy." Photonics 8, no. 10 (September 27, 2021): 412. http://dx.doi.org/10.3390/photonics8100412.

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We applied room-temperature photoluminescence (PL) spectroscopy for the compositional engineering of a CH3NH3Pb(Cl,I)3 light harvester in an alloy-based perovskite solar cell. This spectroscopic characterization determines the optimal Cl concentration where the power conversion efficiency shows its maximum in a contactless and non-destructive manner. The PL quenching ratio evaluated from the comparative PL studies between the films grown on glass/ZrO2 and SnO2:F/TiO2 substrates exhibited its maximum at a Cl concentration of 10 mol%, which agrees with the Cl concentration determined from the current–voltage measurement-based device performance. We also discuss the possible reasons for the coincidence mentioned above regarding the charge extraction effect induced by Cl incorporation.

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Qian, Dou-Dou, Lei Liu, Zhi-Xue Xing, Rui Dong, Li Wu, Hong-Kun Cai, Yong-Fa Kong, Yi Zhang, and Jing-Jun Xu. "Improvement of Photoluminescence of Perovskite CH₃NH₃PbI₃ by Adding Additional CH₃NH₃I during Grinding." Chinese Physics Letters 38, no. 8 (September 1, 2021): 087801. http://dx.doi.org/10.1088/0256-307x/38/8/087801.

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The organic-inorganic hybrid perovskite CH3NH3PbI3 has been a good candidate for many optoelectronic applications such as light-emitting diodes due to its unique properties. Optimizing the optical properties of the CH3NH3PbI3 material to improve the device performance is a hot topic. Herein, a new strategy is proposed to enhance the light emission of CH3NH3PbI3 phosphor effectively. By adding the reactant CH3NH3I powder in an appropriate proportion and simply grinding, the emission intensity of CH3NH3PbI3 is greatly improved. The advantages of the proposed method are swiftness, simplicity and reproducibility, and no requirement for a complex organic ligand. The mechanism of this phenomenon is revealed by x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, photoluminescence, and temperature-dependent photoluminescence. This study offers a unique insight for optimizing the optical properties of halide perovskite materials.

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Suta, Markus, and Claudia Wickleder. "Photoluminescence of CsMI3:Eu2+ (M = Mg, Ca, and Sr) – a spectroscopic probe on structural distortions." Journal of Materials Chemistry C 3, no. 20 (2015): 5233–45. http://dx.doi.org/10.1039/c5tc00515a.

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Choi, Hoyeon, Jack Chun-Ren Ke, Stefan Skalsky, Christopher A. Castle, Kexue Li, Katie L. Moore, Wendy R. Flavell, and Patrick Parkinson. "Visualizing the role of photoinduced ion migration on photoluminescence in halide perovskite grains." Journal of Materials Chemistry C 8, no. 22 (2020): 7509–18. http://dx.doi.org/10.1039/d0tc01441a.

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By combining in situ optical spectroscopy with a high spatial resolution mass spectrometry, we directly link the evolution in carrier recombination processes in perovskite films to light-induced ion migration.

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38

Dai, Qilin, Yifang Qi, and Qiqi Zhang. "Perovskite Films Passivated By the Organic Materials for High Efficiency and High Stability Devices." ECS Meeting Abstracts MA2022-02, no. 16 (October 9, 2022): 840. http://dx.doi.org/10.1149/ma2022-0216840mtgabs.

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Perovskite films are attracting much attention due to their excellent optoelectronic properties. The corresponding photovoltaic devices show a record efficiency of 25.7% since 2009, which is very promising to surpass silicon solar cells. The defects of the perovskite films are the major negative factors to achieve high efficiency. The defects of the perovskite films are related to the polycrystal nature of the perovskite films, which is unavoided and caused by the solution-based method. Therefore, high-quality perovskite films with fewer defects are very critical to obtain high-efficiency devices. One strategy is to incorporate some additives into the perovskite solutions to adjust the perovskite film growth toward fewer defects. However, the additives are very limited in this strategy and limited success is reported. The promising strategy is to passivate defects of the films after the film fabrication. We present the passivation of perovskite films by organic materials including polymers, organic small molecules as well as dye molecules. The organic molecules with the special organic functional groups interact with perovskite films to modify the defects of the films to improve the charge transport and reduce charge recombination, leading to improved device performance. The surface defects and the grain boundary defects of the perovskite films are passivated by the organic materials, which is confirmed by the electron/hole only devices, electronic impedance spectroscopy (EIS) studies, photoluminescence, and time-resolved photoluminescence. The device efficiency increases from ~19% to ~21%, which is manifested by the J-V measurements. The passivation mechanism of the devices by organic materials is investigated and demonstrated.

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Chen, Lung-Chien, Kuan-Lin Lee, Kun-Yi Lee, Yi-Wen Huang, and Ray-Ming Lin. "Study of Metal–Semiconductor–Metal CH3NH3PbBr3 Perovskite Photodetectors Prepared by Inverse Temperature Crystallization Method." Sensors 20, no. 1 (January 5, 2020): 297. http://dx.doi.org/10.3390/s20010297.

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Numerous studies have addressed the use of perovskite materials for fabricating a wide range of optoelectronic devices. This study employs the deposition of an electron transport layer of C60 and an Ag electrode on CH3NH3PbBr3 perovskite crystals to complete a photodetector structure, which exhibits a metal–semiconductor–metal (MSM) type structure. First, CH3NH3PbBr3 perovskite crystals were grown by inverse temperature crystallization (ITC) in a pre-heated circulator oven. This oven was able to supply uniform heat for facilitating the growth of high-quality and large-area crystals. Second, the different growth temperatures for CH3NH3PbBr3 perovskite crystals were investigated. The electrical, optical, and morphological characteristics of the perovskite crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy, and photoluminescence (PL). Finally, the CH3NH3PbBr3 perovskite crystals were observed to form a contact with the Ag/C60 as the photodetector, which revealed a responsivity of 24.5 A/W.

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Surdu, Vasile-Adrian, Roxana Doina Trușcă, Bogdan Ștefan Vasile, Ovidiu Cristian Oprea, Eugenia Tanasă, Lucian Diamandescu, Ecaterina Andronescu, and Adelina Carmen Ianculescu. "Bi1−xEuxFeO3 Powders: Synthesis, Characterization, Magnetic and Photoluminescence Properties." Nanomaterials 9, no. 10 (October 16, 2019): 1465. http://dx.doi.org/10.3390/nano9101465.

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Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precursor xerogel was characterized by thermal analysis. Bi1−xEuxFeO3 (x = 0–0.20) powders obtained after thermal treatment of the xerogel at 600 °C for 30 min were investigated by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Mössbauer spectroscopy. Magnetic behavior at room temperature was tested using vibrating sample magnetometry. The comparative results showed that europium has a beneficial effect on the stabilization of the perovskite structure and induced a weak ferromagnetism. The particle size decreases after the introduction of Eu3+ from 167 nm for x = 0 to 51 nm for x = 0.20. Photoluminescence spectroscopy showed the enhancement of the characteristic emission peaks intensity with the increase of Eu3+ concentration.

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Fanizza, Elisabetta, Roberto Schingo, Annamaria Panniello, Angelica Maria Lanza, Nicoletta Depalo, Angela Agostiano, Maria Lucia Curri, and Marinella Striccoli. "CsPbBr3 Nanocrystals-Based Polymer Nanocomposite Films: Effect of Polymer on Spectroscopic Properties and Moisture Tolerance." Energies 13, no. 24 (December 20, 2020): 6730. http://dx.doi.org/10.3390/en13246730.

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Metal halide perovskites nanocrystals (NCs) represent an emerging class of materials that find increasing application in optoelectronic and photovoltaic devices, thanks to their intriguing optical properties, including high absorption coefficient, high fluorescence quantum yield (PL QY) and fast charge carrier separation. However, their opening to market is still hindered by their limited reliability, due to an intrinsic structural instability and degradation of their photophysical properties upon air, moisture, and light exposure. The incorporation of perovskite NCs in polymer matrix can limit some of the NC instability issues, with advantages in film processability, device fabrication and mechanical performance, being also useful for fundamental studies. In this regard, here, nanocomposites based on polymethylmethacrylate or polystyrene embedding all-inorganic CsPbBr3 NCs have been prepared and processed in the form of flexible free-standing films. A systematic spectrofluorimetric study, comprising steady state photoluminescence (PL), PL quantum yield (QY) and PL decay of the free-standing films before and after exposure to relative humidity condition (RH% 85%, at 25 °C) is performed and discussed. Phase segregation phenomena, changes in NC passivation and recombination dynamics are evaluated as a function of polymer loading and its molecular structure and finally the efficacy of the polymer as moisture barrier investigated.

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Zhang, Jiameng, Yanan Hao, Meihua Bi, Guoyan Dong, Xiaoming Liu, and Ke Bi. "Outstanding Photoluminescence in Pr3+-Doped Perovskite Ceramics." Micromachines 9, no. 9 (August 21, 2018): 419. http://dx.doi.org/10.3390/mi9090419.

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Ba (Zr0.2Ti0.8) O3-50% (Ba0.7Ca0.3) TiO3 (BZT-0.5BCT) ceramics with different doping contents of Pr3+ were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Photoluminescence (PL) emission spectra were measured to analyze the PL characteristics. The strong intensities of a green band at 489 nm and a red band at 610 nm were observed. The maximum emission intensity of the PL spectrum was achieved in the BZT-0.5BCT ceramic with 0.2% mol of Pr3+ ions. Furthermore, the PL spectra of BZT-0.5BCT ceramics were found to be sensitive to polarization of the ferroelectric ceramics. Compared with the unpoled ceramics, the green emission increased about 42% and a new emission peak at 430 nm appeared for the poled ceramics. With excellent intrinsic ferroelectricity and an enhanced PL property, such material has potential to realize multifunctionality in a wide application range.

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Peters, John A., Zhifu Liu, Michael C. De Siena, Mercouri G. Kanatzidis, and Bruce W. Wessels. "Photoluminescence spectroscopy of excitonic emission in CsPbCl3 perovskite single crystals." Journal of Luminescence 243 (March 2022): 118661. http://dx.doi.org/10.1016/j.jlumin.2021.118661.

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Xu, Qiang, Wenyi Shao, Xinlei Zhang, Jun Liu, Xiaoping Ouyang, Xiaobin Tang, and Wenbao Jia. "Low-temperature photoluminescence spectroscopy of CH3NH3PbBrxCl3-x perovskite single crystals." Journal of Alloys and Compounds 792 (July 2019): 185–90. http://dx.doi.org/10.1016/j.jallcom.2019.04.016.

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Kafetzi, Martha, Stergios Pispas, and George Mousdis. "Hybrid Perovskite/Polymer Materials: Preparation and Physicochemical Properties." Journal of Composites Science 5, no. 11 (November 19, 2021): 304. http://dx.doi.org/10.3390/jcs5110304.

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The aim of this work is to investigate the preparation, the optical properties, and the stability over time of a colloidal organic–inorganic hybrid perovskite (CH3NH3PbBr3)/random copolymer P(MMA-co-DMAEMA) system. Different ratios of perovskite to copolymer were used to study its effect on stability and properties. The optical properties were investigated by UV-Vis and fluorescence spectroscopy. Dynamic light scattering was used to determine the size, and the size polydispersity of the colloidal hybrid particles; while morphology was investigated by transmission electron microscopy. Photoluminescence decay studies revealed the interaction of the random copolymer with the perovskite. Finally, thin-films were prepared, to investigate the optical properties of the samples in the absence of the solvent. High temporal stability of the optical properties of thin hybrid films was observed under certain conditions.

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Naveen Kumar, B. V., T. Samuel, Samatha Bevara, K. Ramachandra Rao, and Satya Kamal Chirauri. "Bright blue emissions on UV-excitation of LaBO<sub>3</sub> (B=In, Ga, Al) perovskite structured phosphors for commercial solid-state lighting applications." Chimica Techno Acta 9, no. 1 (March 11, 2022): 20229107. http://dx.doi.org/10.15826/chimtech.2022.9.1.07.

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Bright blue photoluminescence (PL) was obtained from Bi3+-activated LaBO3 (B = In, Ga, Al) perovskite nanophosphors. A cost-effective and low-temperature chemical route was employed for preparing Bi3+ doped LaBO3 (B=In, Ga, Al) which were then annealed at 1000 °C. The phase formation, morphological studies and luminescent properties of the as-prepared samples were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence and optical absorption spectroscopy. Comparison of emission intensities, lifetime studies, energy band gaps and color purity of all samples (pure and Bi3+ doped) were investigated for promising applications in UV light-emitting diodes, variable frequency drive (VFD), field emission display (FED), and other photoelectric fields.

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Xiao, Liangyan, Linwei Huang, Weihaojia Su, Tianjun Wang, Haiying Liu, Zhongchao Wei, and Haihua Fan. "Efficiency Enhancement Strategies for Stable Bismuth-Based Perovskite and Its Bioimaging Applications." International Journal of Molecular Sciences 24, no. 5 (March 1, 2023): 4711. http://dx.doi.org/10.3390/ijms24054711.

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Lead-free perovskite is one of the ideal solutions for the toxicity and instability of lead halide perovskite quantum dots. As the most ideal lead-free perovskite at present, bismuth-based perovskite quantum dots still have the problem of a low photoluminescence quantum yield, and its biocompatibility also needs to be explored. In this paper, Ce3+ ions were successfully introduced into the Cs3Bi2Cl9 lattice using a modified antisolvent method. The photoluminescence quantum yield of Cs3Bi2Cl9:Ce is up to 22.12%, which is 71% higher than that of undoped Cs3Bi2Cl9. The two quantum dots show high water-soluble stability and good biocompatibility. Under the excitation of a 750 nm femtosecond laser, high-intensity up-conversion fluorescence images of human liver hepatocellular carcinoma cells cultured with the quantum dots were obtained, and the fluorescence of the two quantum dots was observed in the image of the nucleus. The fluorescence intensity of cells cultured with Cs3Bi2Cl9:Ce was 3.20 times of that of the control group and 4.54 times of the control group for the fluorescence intensity of the nucleus, respectively. This paper provides a new strategy to develop the biocompatibility and water stability of perovskite and expands the application of perovskite in the field.

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Jemli, Khaoula, Hiba Diab, Ferdinand Lédée, Gaelle Trippé-Allard, Damien Garrot, Bernard Geffroy, Jean-Sébastien Lauret, Pierre Audebert, and Emmanuelle Deleporte. "Using Low Temperature Photoluminescence Spectroscopy to Investigate CH3NH3PbI3 Hybrid Perovskite Degradation." Molecules 21, no. 7 (July 8, 2016): 885. http://dx.doi.org/10.3390/molecules21070885.

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Zou, Long, Han Xing Liu, L. L. Guo, Guo Tao Xu, and Gai Feng Xue. "Preparation and Characterization of Organic-Inorganic Hybrid Perovskite (C₆H₅CH₂NH₃)₂CuCl₄." Advanced Materials Research 311-313 (August 2011): 2146–50. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.2146.

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An organic–inorganic hybrid perovskite (C6H5CH2NH3)2CuCl4was synthesized successfully by solution method at room temperature and the thin film of (C6H5CH2NH3)2CuCl4 was also prepared by spin-coating on the quartz substrate. The perovskite and the film were characterized with X-ray diffraction (XRD), Scan electronic microscope (SEM), Atomic force microscope (AFM), Fourier transform infrared spectroscopy and Thermo Gravimetric Analyzer. Results show that the obtained perovskite has unique layer structure and good thermal stability with melting point around 243.3°C. And the prepared film appears very smooth, continuous and uniform with a grain size of 0.1μm, highly oriented with the (0 0 l) planes perpendicular to the substrate surface. Its optical photoluminescence spectrum mainly depends on the inorganic part so the bandgap can be tuned by changing the inorganic composition. The carrier mobility is around 0.26cm2V-1S-1 , which indicates its potential application in field effect transistor with improved film quality.

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Hou, Lei, Philippe Tamarat, and Brahim Lounis. "Revealing the Exciton Fine Structure in Lead Halide Perovskite Nanocrystals." Nanomaterials 11, no. 4 (April 20, 2021): 1058. http://dx.doi.org/10.3390/nano11041058.

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Lead-halide perovskite nanocrystals (NCs) are attractive nano-building blocks for photovoltaics and optoelectronic devices as well as quantum light sources. Such developments require a better knowledge of the fundamental electronic and optical properties of the band-edge exciton, whose fine structure has long been debated. In this review, we give an overview of recent magneto-optical spectroscopic studies revealing the entire excitonic fine structure and relaxation mechanisms in these materials, using a single-NC approach to get rid of their inhomogeneities in morphology and crystal structure. We highlight the prominent role of the electron-hole exchange interaction in the order and splitting of the bright triplet and dark singlet exciton sublevels and discuss the effects of size, shape anisotropy and dielectric screening on the fine structure. The spectral and temporal manifestations of thermal mixing between bright and dark excitons allows extracting the specific nature and strength of the exciton–phonon coupling, which provides an explanation for their remarkably bright photoluminescence at low temperature although the ground exciton state is optically inactive. We also decipher the spectroscopic characteristics of other charge complexes whose recombination contributes to photoluminescence. With the rich knowledge gained from these experiments, we provide some perspectives on perovskite NCs as quantum light sources.

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Journal articles on the topic 'Perovskites, photoluminescence spectroscopy'

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