Literatura académica sobre el tema "Nanohoops, organic semiconductors"

Harvesting energetic carriers from plasmonic resonance has been a hot topic in the field of photodetection in the last decade. By interfacing a plasmonic metal with a semiconductor, the photoelectric conversion mechanism, based on hot carrier emission, is capable of overcoming the band gap limitation imposed by the band−to−band transition of the semiconductor. To date, most of the existing studies focus on plasmonic structural engineering in a single metal–semiconductor (MS) junction system and their responsivities are still quite low in comparison to conventional semiconductor, material−based photodetection platforms. Herein, we propose a new architecture of metal−semiconductor–metal (MSM) junctions on a silicon platform to achieve efficient hot hole collection at infrared wavelengths with a photoconductance gain mechanism. The coplanar interdigitated MSM electrode’s configuration forms a back−to−back Schottky diode and acts simultaneously as the plasmonic absorber/emitter, relying on the hot−spots enriched on the random Au/Si nanoholes structure. The hot hole−mediated photoelectric response was extended far beyond the cut−off wavelength of the silicon. The proposed MSM device with an interdigitated electrode design yields a very high photoconductive gain, leading to a photocurrent responsivity up to several A/W, which is found to be at least 1000 times higher than that of the existing hot carrier based photodetection strategies.

Organic–inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO2-polyvinylpyrrolidone (ox-SWCNH/SnO2/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection in dry air, in the range from 0 up to 50 mg/L. All the sensing films had an ox-SWCNH concentration in the range of 33.3–62.5 wt%. A comparison between the transfer functions and the response and recovery times of these sensing devices has shown that the structures with ox-SWCNH/SnO2/PVP = 1/1/1 have the highest relative sensitivities of 0.0022 (mg/L)−1, while the devices with ox-SWCNH/SnO2/PVP = 2/1/1 have the lowest response time (15 s) and recovery time (50 s) for a room temperature operation, proving the key role of carbonic material in shaping the static and dynamic performance of the sensor. These response and recovery times are lower than those of “heated” commercial sensors. The sensing mechanism is explained in terms of the overall response of a p-type semiconductor, where ox-SWCNH percolated between electrodes of the sensor, shunting the heterojunctions made between n-type SnO2 or ZnO and p-type ox-SWCNH. The hard–soft acid–base (HSAB) principle supports this mechanism. The low power consumption of these devices, below 2 mW, and the sensing performances at room temperature may open new avenues towards ethanol sensors for passive samplers of environment monitoring, alcohol test portable instruments and wireless network sensors for Internet of Things applications.

We report the relative humidity (RH) sensing response of a resistive sensor, employing sensing layers, based on a quaternary organic–inorganic hybrid nanocomposite comprising oxidized carbon nanohorns (CNHox), graphene oxide (GO), tin dioxide, and polyvinylpyrrolidone (PVP), at 1/1/1/1 and 0.75/0.75/1/1/1 mass ratios. The sensing structure comprises a silicon substrate, a SiO2 layer, and interdigitated transducer (IDT) electrodes. The sensing film was deposited via the drop-casting method on the sensing structure. The morphology and the composition of the sensing layers were investigated through Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and RAMAN spectroscopy. The organic–inorganic quaternary hybrid-based thin film’s resistance increased when the sensors were exposed to relative humidity ranging from 0 to 100%. The manufactured devices show a room temperature response comparable to that of a commercial capacitive humidity sensor and characterized by excellent linearity, rapid response and recovery times, and good sensitivity. While the sensor with CNHox/GO/SnO2/PVP at 0.75/0.75/1/1 as the sensing layer has the best performance in terms of linearity and recovery time, the structures employing the CNHox/GO/SnO2/PVP at 1/1/1/1 (mass ratio) have a better performance in terms of relative sensitivity. We explained each constituent of the quaternary hybrid nanocomposites’ sensing role based on their chemical and physical properties, and mutual interactions. Different alternative mechanisms were taken into consideration and discussed. Based on the sensing results, we presume that the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of PVP, dominates and leads to the overall increasing resistance of the sensing layer. The hard–soft acid–base (HSAB) principle also supports this mechanism.

AbstractSince the first applications of nanohoops in organic electronics appear promising, the time has come to go deeper into their rational design in order to reach high‐efficiency materials. To do so, systematic studies dealing with the incorporation of electron‐rich and/or electron‐poor functional units on nanohoops have to be performed. Herein, the synthesis, the electrochemical, photophysical, thermal, and structural properties of two [4]cyclo‐2,7‐carbazoles, [4]C‐Py‐Cbz, and [4]C‐Pm‐Cbz, possessing electron‐withdrawing units on their nitrogen atoms (pyridine or pyrimidine) are reported. The synthesis of these nanohoops is first optimized and a high yield above 50% is reached. Through a structure‐properties relationship study, it is shown that the substituent has a significant impact on some physicochemical properties (eg HOMO/LUMO levels) while others are kept unchanged (eg fluorescence). Incorporation in electronic devices shows that the most electrically efficient Organic Field‐Effect transistors are obtained with [4]C‐Py‐Cbz although this compound does not present the best‐organized semiconductor layer. These experimental data are finally confronted with the electronic couplings between the nanohoops determined at the DFT level and have highlighted the origin in the difference of charge transport properties. [4]C‐Py‐Cbz has the advantage of a more 2D‐like transport character than [4]C‐Pm‐Cbz, which alleviates the impact of defects and structural organization.

L’électronique organique (EO) s’articule autour de l’utilisation des semi-conducteurs organiques (SCOs). Les diodes organiques électroluminescentes (OLEDs) font partie des technologies électroniques les plus matures et sont déjà présentes dans nos smartphones, ordinateurs et téléviseurs. Durant cette thèse, nous nous sommes particulièrement intéressés à l’élaboration de matrices hôtes pour la seconde génération d’OLEDs : les diodes organiques électrophosphorescentes (PhOLEDs). Deux design moléculaires différents ont été conçus avec deux objectifs différents. Le premier objectif consiste à développer de nouvelles matrices hôtes utilisant l’architecture Donneur-spiro-Accepteur pour des PhOLEDs monocouches, qui sont des dispositifs simplifiés utilisant seulement les électrodes et la couche émissive. Ces travaux ont conduit à la fabrication de PhOLEDs monocouches des trois couleurs présentes dans un pixel (rouge, vert et bleu), et des couleurs pour l’éclairage (jaune et blanc). Des records de performances ont été obtenus. Le deuxième objectif consiste à développer de nouveaux SCOs appelés nano-anneaux. Après un chapitre bibliographique analysant les performances des nano-anneaux en EO, nous présenterons une étude de structure/propriétés de nano-anneaux donneur-accepteur. Ces travaux, nous ont permis de mieux comprendre les propriétés singulières de ces composés cycliques à base de carbazoles, qui ont ensuite ont été incorporés dans des PhOLEDs multicouches pour évaluer leurs performances en tant que matrice hôtes. Ces travaux représentent les premiers exemples du domaine
Organic electronics (EO) is based on organic semiconductors (OSCs). Organic light-emitting diodes (OLEDs) are among the most mature EO technologies and are already present in our smartphones, computers and televisions. During this thesis, we were particularly interested in the development of host materials for the second generation of OLEDs: organic electrophosphorescent diodes (PhOLEDs). Two different molecular designs have been elaborated with two different objectives. The first objective was to develop new host materials using the Donor-spiro-Acceptor architecture for single-layer PhOLEDs, which are simplified devices using only the electrodes and the emissive layer. This work has enabled the fabrication of single-layer PhOLEDs in the three colours present in a pixel (red, green and blue) and in the colours used for lighting (yellow and white). Device performance records have been obtained. The second objective was to develop new SCOs, with a cylindric shape, called nanohoops. After a bibliographic chapter analysing the performance of nanohoops in EO, we present a structure/properties study of Donor-Acceptor nanohoops. This work enabled us to gain a better understanding of the unique properties of these carbazole-based nanohoops, which were then incorporated into multilayer PhOLEDs to measure their performances. This work provides the first exemples of the field