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Photovoltaic Properties of Polymer Film Composites with a Tetranuclear Copper Complex Cu4L4(OCH3)4 (L? = N,N′-Dibenzyl-N″-Trichloroacetylphosphotriamide)
摘要： A study was carried out on the photovoltaic and photoconductive properties of film composites of a copolymer of styrene with nonyl methacrylate and poly-N-epoxypropylcarbazole doped with the tetranuclear metal (L(cid:2) = N,N(cid:3)-dibenzyl-N(cid:3)(cid:3)-trichloroacetylphosphotriamide) using an organic complex Cu4L4(OCH3)4 intramolecular charge transfer compound as a sensitizer. In the visible spectrum, these composites have hole-type photoconductivity, while their internal photoelectric effect is related to the photogeneration of charge carriers from the metal complex molecules and the sensitizer. The metal complex molecules in the polymer composite were found to increase the efficiency of photogeneration of nonequilibrium charge carriers and thereby affect the photovoltaic properties of the composites.
关键词： polymer composites,metal complex,photovoltaics,photoconductivity,spin conversion
更新于2025-09-12 10:27:22
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Strong bulk photovoltaic effect in chiral crystals in the visible spectrum
摘要： Structurally chiral materials hosting multifold fermions with large topological number have attracted considerable attention because of their naturally long surface Fermi arcs and bulk quantized circular photogalvanic effect (CPGE). Multifold fermions only appear in metallic states, and therefore most studies so far have only focused on the semimetals in compounds with chiral crystal structures. In this work, we show that the structurally chiral topological trivial insulators are also exotic states, which is interesting from the application point of view, owing to their natural advantage to host a large bulk photovoltaic effect in the visible wavelength region. In recent decades, the shift current in the visible wavelength region was limited to be 10 μA/V2 in all the experimentally measured reports. By scanning the insulators with chiral structure, we found a class of compounds with photoconductivity ranging from ～20 to ～80 μA/V2, which is comparable to the largest reported shift current. This work illustrates that the compounds with chiral structure can host both quantum CPGE and a strong shift current in the second-order optical response. Moreover, this work offers a good platform for the study of the shift current and its future application by putting the focus on insulators with chiral lattices, so far overlooked in photovoltaic technologies.
关键词： photoconductivity,chiral crystals,shift current,bulk photovoltaic effect,visible spectrum
更新于2025-09-12 10:27:22
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Bias Tunable Photocurrent in Metal-Insulator-Semiconductor Heterostructures with Photoresponse Enhanced by Carbon Nanotubes
摘要： Metal-insulator-semiconductor-insulator-metal (MISIM) heterostructures, with rectifying current-voltage characteristics and photosensitivity in the visible and near-infrared spectra, are fabricated and studied. It is shown that the photocurrent can be enhanced by adding a multi-walled carbon nanotube film in the contact region to achieve a responsivity higher than 100 mA W?1 under incandescent light of 0.1 mW cm?2. The optoelectrical characteristics of the MISIM heterostructures are investigated at lower and higher biases and are explained by a band model based on two asymmetric back-to-back Schottky barriers. The forward current of the heterojunctions is due to majority-carrier injection over the lower barrier, while the reverse current exhibits two different conduction regimes corresponding to the diffusion of thermal/photo generated carriers and majority-carrier tunneling through the higher Schottky barrier. The two conduction regimes in reverse bias generate two plateaus, over which the photocurrent increases linearly with the light intensity that endows the detector with bias-controlled photocurrent.
关键词： Schottky junctions,carbon nanotubes,photoconductivity,heterostructures,MISIM
更新于2025-09-12 10:27:22
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Suppression of persistent photoconductivity AlGaN/GaN heterostructure photodetectors using pulsed heating
摘要： This paper demonstrates a method to reduce the decay time in AlGaN/GaN photodetectors by pulsed heating mode. A suspended AlGaN/GaN heterostructure photodetector integrated with micro-heater is fabricated and characterized under ultraviolet illumination. We have observed that the course of persistent photoconductivity (PPC) was effectively accelerated by applying pulsed heating. The decay time is significantly reduced from 175 s by DC heating to 116 s by 50 Hz pulsed heating at the same power (280 mW). With the same pulse duty cycle and 50 Hz pulsed heating frequency, a reduction of 30-45 % in decay time is measured compared to DC heating.
关键词： pulsed heating,persistent photoconductivity,decay time,AlGaN/GaN heterostructure,photodetectors
更新于2025-09-11 14:15:04
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UV-visible photoresponse properties of self-seeded and polymer mediated ZnO flower-like and biconical nanostructures
摘要： Nano-sized zinc oxide (ZnO) flowers and bicones have been prepared by a co-precipitation method using ZnO-seed for flowers and polyethylene glycol (PEG) for bicones to study their photoconductivity under UV-vis illumination. As-synthesized ZnO samples were characterized by various techniques. XRD spectra show that both samples exhibit hexagonal wurtzite structure of ZnO. FESEM images show the morphology of ZnO as that of flower-shaped structures and bicone-shaped structures respectively. UV-visible absorption spectra of both samples have two absorption band edges due to bicone-like structure. ZnO bicones exhibit high photosensitivity as compared to ZnO flowers. However, vacuum is found enhancing the photosensitivity of ZnO bicones as compared to that in air.
关键词： Bicones,ZnO,Seed,PEG,Flowers,Photoconductivity
更新于2025-09-11 14:15:04
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Structural, Optical, Mechanical and Laser Damage Threshold Studies on an active Nonlinear Optical Material: Potassium Thiourea Bromide (KTB) in a Novel Crystal System
摘要： The enhancement of optical transparency, crystalline perfection, laser damage threshold values and principally, mechanical strength of thiourea doped potassium bromide crystals grown under slow evaporation solution growth technique were assessed. The validation and morphology were done by X-ray diffraction analysis. The sample KTB crystallized in orthorhombic system is unique and novel. The vibrational range in the FT-IR affirmed the functional groups present in the title compound. The energy gap Eg found to be 4.12eV with broad transparency window between 300.600nm to 1100nm. Second harmonic studies manifest the suitability of the crystal for frequency conversion and doubling applications. The positive photo conducting nature of the material aspires that the sample would be more electrically conductive on the absorption of electromagnetic radiation. The laser damage threshold value indicates the aptness of the sample to confront against high power intensities. The elastic(C11), plastic, fracture traits(Kc) along with the yield strength(σv) and brittleness index(Bi) were calculated and reported for the first time under orthorhombic system. The result also evident appreciable mechanical strength of the crystal, as it holds cardinal importance in technological applications.
关键词： Crystal growth,Mechanical properties,Non linear optical material,Characterization,LDT,Photoconductivity
更新于2025-09-11 14:15:04
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Electrical Properties of Indium-Oxide Thin Films Produced by Plasma-Enhanced Reactive Thermal Evaporation
摘要： The structure and electrical properties of transparent indium-oxide thin films produced by plasma-enhanced reactive thermal evaporation at different substrate temperatures are studied. It is found that the films have a grained structure. An increase in the substrate temperature yields a considerable increase in the conductivity of the films and a decrease in the photoconductivity-relaxation time. An interpretation of the effect of the substrate temperature on the observed changes in the electrical and photoelectric properties of the indium-oxide films under study is proposed.
关键词： indium-oxide thin films,electrical properties,substrate temperature,photoconductivity,plasma-enhanced reactive thermal evaporation
更新于2025-09-11 14:15:04
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Oxygen vacancy induced photoconductivity enhancement in Bi <sub/> 1- <i>x</i> </sub> Ca <i> <sub/>x</sub></i> FeO <sub/>3-δ</sub> nanoparticle ceramics: A combined experimental and theoretical study
摘要： Based on experimental and density functional studies, we show that tailoring of oxygen vacancies (OV) leads to large scale enhancement of photoconductivity in BiFeO3 (BFO). The OV concentration is increased by substituting an aliovalent cation Ca2+ at Bi3+ sites in the BFO structure. Furthermore, the OV concentration at the disordered grain boundaries can be increased by reducing the particle size. Photoconductivity studies carried out on spark plasma sintered Bi1-xCaxFeO3-δ ceramics show four orders of enhancement for x = 0.1. Temperature dependent Nyquist plots depict a clear decrease in impedance with increasing Ca2+ concentration which signi?es the role of OV. A signi?cant reduction in photoconductivity by 2 to 4 orders and a large increase in impedance of the air-annealed (AA) nanocrystalline ceramics suggest that OV at the grain boundaries primarily control the photocurrent. In fact, activation energy for AA samples (0.5 to 1.4 eV) is larger than the as-prepared (AP) samples (0.1 to 0.5 eV). Therefore, the room temperature J-V characteristics under 1 sun illumination show 2–4 orders more current density for AP samples. Density-functional calculations reveal that, while the defect states due to bulk OV are nearly ?at, degenerate, and discrete, the defect states due to surface OV are non-degenerate and interact with the surface dangling states to become dispersive. With large vacancy concentration, they form a defect band that enables a continuous transition of charge carriers leading to signi?cant enhancement in the photoconductivity. These studies reveal the importance of tailoring the microstructural features as well as the composition-tailored properties to achieve large short circuit current in perovskite oxide based solar cells.
关键词： density functional theory,BiFeO3,spark plasma sintering,Ca doping,oxygen vacancies,photoconductivity
更新于2025-09-11 14:15:04
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Light-Induced Current Oscillations in the Charge-Ordered State of (TMTTF)2SbF6
摘要： Below TCO = 157 K the quasi-one-dimensional charge-transfer salt (TMTTF)2SbF6 undergoes a pronounced phase transition to a charge-ordered ground state. We have explored the non-linear and photoconductive behavior as a function of applied voltage, laser pulse energy and temperature. Besides a decay of the photoconductive signal in a double exponential fashion in the millisecond range, we discover current oscillations in the kHz range induced by the application of short laser pulses. While the resonance frequencies do not depend on voltage or laser intensity and vary only slightly with temperature, the amplitude changes linearly with the laser intensity and voltage. We suggest that photo-induced fluctuations of the charge-ordered state alter the current flow of the single particles and hence, the photocurrent. The findings are discussed and compared to comparable phenomena in other low-dimensional electron systems.
关键词： TMTTF,non-linear transport,calculations of band structure and optical conductivity,charge-transfer salts,photoconductivity,current oscillations,charge-order phase transition
更新于2025-09-11 14:12:44
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Studies on the photoelectric properties of crosslinked-poly(acrylamide co-acrylic acid) for photo detector applications
摘要： The co-polymer, polyacrylamide co-acrylic acid-P(AM-AA) was prepared by chemical polymerization of acrylamide with acrylic acid in presence of methylene bisacrylamide as a crosslinker. The copolymer was analyzed using FTIR, XRD and DTA. The I-V characteristics of the copolymer were studied and proved that the recombination process is dependent on the presence of traps distributed in the energy gap. The results showed that the traps contribute significantly in the increased photosensitivity of the co-polymer. The behaviors of both dark and photoconductivity with temperature showed linear relations at different light intensities and proved an activated conduction with single activation energy. The activation energy (Ea) at different light intensity was found to follow Meyer Neldel rule (MN rule) and the intercept σo (pre factor) as well. The characteristic energy of exponential traps was found to be within 0.0134–0.009 eV, at different light intensities. The transient photoconductivity studies on the co-polymer confirmed the presence of traps. Where, the high photosensitivity and the presence of traps may contribute to the development of the improved performance of photo detectors.
关键词： Polyacrylamide co-acrylic acid,Meyer-Neldel rule,Photoconductivity
更新于2025-09-10 09:29:36