Academic literature on the topic 'CuInS2 QD'

Abstract Simulation studies have been carried out for the n–i–p perovskite solar cell (PSC) structure i.e. ITO/SnO2/CH3NH3PbI3/CuInS2/Au. We have considered this cell as our primary structure and is simulated using solar cell capacitance simulator-1D software. Here, the CuInS2 quantum dot (CIS QD) acts as an inorganic hole transporting layer. Further, the use of the CIS QD in PSCs has been explored by simulating 20 different cell structures. These PSCs are based on recently used absorber layers, i.e. MASnI3, FAPbI3, and (FAPbI3)0.97 (MAPbBr1.5Cl1.5)0.03, and electron transporting layers, i.e. SnO2, TiO2, ZnO, C60, and IGZO. The performance of all structures has been optimized by varying the thickness of the absorber layers and electron transporting layers. The cell structure, ITO/SnO2/CH3NH3SnI3/CuInS2/Au, has been found to exhibit the highest power conversion efficiency of 21.79% as compared to other cells. Investigations have also been carried out to analyze the effect of defect density in the absorber layer and the interface of the cell structure. In addition, the cell performance has been ascertained by examining the impact of operating temperature, metal contact work function and that of resistance in series as well as in parallel. The simulation results of our primary cell structure are found to be in good agreement with the recent experimental study.

Nanocomposites combining functional nanoparticles and transparent polymers allow for stabilization of filler properties over long periods of time while retaining transparency of the polymer matrix. Here we employ CuInS2/ZnS quantum dots (QDs), ternary visible- and NIR-emitting semiconductors as wavelength-tunable luminescent fillers. Luminescence in the near infrared (NIR) is of particular interest in medicine which allows deep penetration into human tissue enabling in vivo diagnostics and treatment, while visible emitters may serve as color converters in displays or lighting. To stabilize the optical properties of QDs and prevent agglomeration, polymethyl metacrylate (PMMA) was chosen as a matrix. These novel polymer nanocomposites (PNCs) show good optical properties and stability under ambient conditions, and can be easily deposited over large areas. High-quality QDs and hydrophobic functionalization with long-chain hydrocarbons are a prerequisite for embedding into a PMMA matrix. Transparent PNC films without visible scattering losses were obtained for 1 wt-% QD loading with respect to the polymer. Partial transparency is retained up to 10 wt-% QD loading and vanishes rapidly at higher loading. Luminescence properties increase up to 5 wt-% and then decrease rapidly due to QD agglomeration and reabsorption between adjacent particles. Potential applications include converter materials for medical applications, laser layers, displays and white LEDs.

We found that core–shell CuInS₂/ZnS QDs have obvious temperature dependence and they can be used for accurate intracellular and in vivo temperature sensing after being encapsulated by micelles, which exhibit high intracellular and in vivo thermal sensitivity.

Semiconductor nanocrystal quantum dots (QDs) are promising materials for solar energy conversion because of their bandgap tunability, high absorption coefficient, and improved hot-carrier generation. CuInSe2 (CISe)-based QDs have attracted attention because of their low toxicity and wide light-absorption range, spanning visible to near-infrared light. In this work, we study the effects of the surface ligands of colloidal CISe QDs on the photoelectrochemical characteristics of QD-photoanodes. Colloidal CISe QDs with mono- and bifunctional surface ligands are prepared and used in the fabrication of type-II heterojunction photoanodes by adsorbing QDs on mesoporous TiO2. QDs with monofunctional ligands are directly attached on TiO2 through partial ligand detachment, which is beneficial for electron transfer between QDs and TiO2. In contrast, bifunctional ligands bridge QDs and TiO2, increasing the amount of QD adsorption. Finally, photoanodes fabricated with oleylamine-passivated QDs show a current density of ~8.2 mA/cm2, while those fabricated with mercaptopropionic-acid-passivated QDs demonstrate a current density of ~6.7 mA/cm2 (at 0.6 VRHE under one sun illumination). Our study provides important information for the preparation of QD photoelectrodes for efficient photoelectrochemical hydrogen generation.

Two-dimensional Transition metal dichalcogenides (TMDCs), have now attracted much attention due to their unique layered structure and physical properties. Up to date, several studies have demonstrated monolayered and few-layered TMDC-based photodetectors with good stability, photo-switching time and broadband detectivity from UV to infrared light region. However, the reported responsivity is not as high as the theoretical expectation, indicating that the light absorption is limited by the atomic thickness of 2D-TMDCs and could still be improved. To overcome the drawback of low absorption in 2D TMDC materials, previous reports have revealed several strategies to enhance the electric field and light-harvesting in these atomically thin TMDC layers by hybridizing plasmonic noble-metal nanoparticles, such as Pt, Au and Ag, to facilitate the light-matter interaction at the surface of semiconductors. In this regard, we aim to combine highly absorptive CuInS2(CIS) nanocrystals with noble metal nanoparticles as the photosensitizer to enhance the intrinsic absorptivity and promote the performance of MoS2-based photodetectors. The interests of noble nanocrystals such as platinum and gold are featured for their distinctive properties of the carrier transportation and the storage when combined with semiconductor materials. The strategy described here acts as a perspective to significantly improve the performance of MoS2-based photodetectors with outstanding detection responsivity with selectable wavelengths by further controlling the size and material of the decorated CIS nanocrystals. In addition to optical sensing, TMDCs have also been developed as a promising candidate for gas-molecule detection. Different from commercial metal oxide gas sensors, TMDCs as sensing materials can be operated at room temperature with good performance, increasing its reliability for future industrial applications. Nevertheless, the relatively low response and long response/recovery time are the main drawbacks of these promising devices. Therefore, we proposed the approach to successfully increase the surface area of TMDCs by a one-step synthesis from WO3 into three-dimensional (3D) WS2 nanowalls through a rapid heating and rapid cooling process. Moreover, the combination of CdS/ZnS or CdSe/ZnS core/shell quantum dots (QDs) with different emission wavelengths and WS2 nanowalls will further improve the performance of WS2-based photodetector devices, including 3.5~4.7 times photocurrent enhancement and shorter response time. The remarkable results of the QD-WS2 hybrid devices to the high non-radiative energy transfer (NRET) efficiency between QDs and our nanostructured material are caused by the spectral overlap between the emission of QDs as the donors and the absorption of WS2 as the acceptors. Additionally, the outstanding NO2 gas-sensing properties of QDs/WS2 devices were demonstrated with a remarkably low detection limit down to 50 ppb with a fast response time of 26.8 s, contributed by tremendous local p-n junctions generated from p-type WS2 nanowalls and n-type CdSe-ZnS QDs in this hybrid system. Our strategies to combine 0D nanoparticles or quantum dots and 2D TMDC materials can significantly enhance the optical sensing and gas molecule sensing properties compared to pristine TMDC-based devices, resulting from the efficient charge or energy transfer between the multi-dimension material system and the creation of local p-n junctions. Moreover, the scalability of these hybrid nanostructures allows our devices to exhibit much more possibilities in advanced multifunctional applications.

Quantum dots (QDs) are semiconductor nanoparticles, where carriers are confined in regions smaller than a few tens of nanometers. The physics governing the behavior of these nano structures are fundamentally different from their bulk counterpart. This thesis studies the dissipative phenomena in QDs. In chapter 1, I give a brief introduction of QDs and their carrier dissipation dynamics. In chapter 2, I show that in CuInS2/CdS QDs, the spontaneous emission (SE) lifetime evolves from 46 ns to ~ 300 ns over a 15 ps time scale due to the collapse of the hole to the intragap states through dissipation. This is also observed in other chalcopyrite QDs. The results are obtained employing upconversion photoluminescence (UPL) measurements. In chapter 3, I try to understand the dissipation dynamics in chalcopyrite QDs by theoretical modelling. The study confirms the ultrafast hole localization in the system due to strong electron-phonon coupling as observed experimentally. However, the system possesses a very high defect-assisted SE lifetime which suggests that along with the vibrational coupling, fine-structure participation also needs to be considered which arises due to the involvement of copper d-orbitals to the valence band of the QDs. In chapter 4, I try to regulate dissipation through controlling SE rate by activating alternative radiative channels. For that, I consider CuCdZnSe QD alloys. From the UPL measurement, I find that this scheme enables us to tune SE lifetimes by three orders of magnitude, from ~ 15 ns to over ~ 7 μs. In chapter 5, I probe the ultrafast carrier dynamics of CuAlS2/ZnS QDs, which directly convert aqueous solutions of bicarbonate ions to formate with remarkable efficiency (~ 20 %). Here I show that it is essentially dominated by ultrafast electron transfer (560 fs) to the surface. In addition, I observe that the electron dwell time in the conduction band increases with the excitation fluence which is reverse of the auger recombination. I further investigate this system through two-pump transient absorption which show that the electron dynamics are governed by the temporal evolution of the hole wave function. In chapter 6, I utilize the dissipation in QDs and build all-optical switching and all-optical logic gates implementing microbubble. The experiments are done using low power continuous-wave laser. In conclusion, I have studied the carrier dissipation dynamics in QDs and built all-optical switching and universal all-optical logic gates which paves the way for the design of photonic circuits.
Indian Institute of Science