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heterostructures: Examination of spin relaxation mechanism
摘要： The thickness, temperature, and composition studies of spin diffusion length (SDL) and spin Hall angle (SHA) are performed by measuring the spin Hall magnetoresistance in Pd1?xPtx/Y3Fe5O12 (=YIG) heterostructures. The SDL is found to be invariant to changes in the electron momentum relaxation time by varying the temperature, the normal metal (NM) thickness, or the alloy composition, while the SHA exhibits a nonmonotonic dependence on temperature. These findings suggest the appearance of D’yakonov-Perel’ spin relaxation mechanism and phonon skew scattering in our heterostructures that is associated with strong interfacial Rashba spin-orbit coupling (IRSOC). At last, we employ the ab initio calculations to quantify the IRSOC at the inversion-symmetry-broken NM/YIG interface.
关键词： spin diffusion length,spin relaxation mechanism,spin Hall angle,interfacial Rashba spin-orbit coupling,PdPt/YIG heterostructures
更新于2025-09-23 15:23:52
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Electron Diffusion Length and Charge Separation Efficiency in Nanostructured Ternary Metal Vanadate Photoelectrodes
摘要： Ternary metal vanadates have recently emerged as promising photoelectrode materials for sunlight-driven water splitting. Here, we show that highly active nanostructured BiVO4 films can be deposited onto fluorine-doped tin oxide (FTO) substrates by a facile sequential dipping method known as successive ionic layer adsorption and reaction (SILAR). After annealing and deposition of a cobalt phosphate (Co-Pi) co-catalyst, the photoelectrodes produce anodic photocurrents (under 100 mW cm-2 broadband illumination, 1.23 V vs. RHE) in pH 7 phosphate buffer that are on par with the highest reported in the literature for similar materials. To gain insight into the reason for the good performance of the deposited films, and to identify factors limiting their performance, incident photon-to-electron conversion efficiency spectra have been analyzed using a simple diffusion–reaction model to quantify the electron diffusion length (Ln; the average distance travelled before recombination) and charge separation efficiency (ηsep) in the films. The results indicate that ηsep approaches unity at sufficiently positive applied potential but the photocurrent is limited by significant charge collection losses due to a short Ln relative to the film thickness. The Co-Pi catalyst is found to improve ηsep at low potentials as well as increase Ln at all potentials studied. These findings help to clarify the role of the Co-Pi co-catalyst and show that there could be room for improvement of BiVO4 photoanodes deposited by SILAR if Ln can be increased.
关键词： charge separation efficiency,ternary metal vanadates,SILAR,electron diffusion length
更新于2025-09-23 15:22:29
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Interfacial engineering revolutionizers: perovskite nanocrystals and quantum dots accentuated performance enhancement in perovskite solar cells
摘要： Utilization of efficient nanomaterials in perovskite solar cells (PSCs) for effectual conversion of solar energy to electrical energy has prompted the extensive progression of PSCs as a suitable alternative to silicon-based photovoltaic (PV) technologies. Most recent progressions are inclusive of nanoscale materials incorporation particularly nanocrystals (NCs) and quantum dots (QDs) with unique sizes, morphological and compositional aspects aimed at PSCs modification. In all conventional architectures of the PSCs, there are number of interfaces between the transport layers and active absorber perovskite layer. Nanocrystals and quantum dots have been employed for the interfacial engineering in PSCs owing to their remarkable optoelectronic and photo-physical characteristics favoring the facile and efficient power generation and reducing dependence on silicone-based PVs. Myriad of NCs and QDs having inorganic and/or inorganic perovskite composition have been investigated, however, the overall synthetic costs, procedural complications, current, and voltage (J–V) hysterical response and stability toward air and light needs further meticulous investigations due to which PV community has been disseminating experimental results rapidly since last few years. Considering the potential of perovskite NCs and QDs, current review has for the first time explored the most recent progressions done in utilization of these nanoscale materials in augmenting PSCs PV functionality through interface modification. Magnifying extent of nanoscale materials for PSCs modification and current investigation signifies the future candidacy of perovskite NCs and QDs as humanity gallants for provisioning of cheaper and sustainable power sources.
关键词： Absorptivity,photovoltaics,bandgap,diffusion length,charge transfer
更新于2025-09-23 15:21:01
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Extraction of the minority carrier transport properties of solar cells using the Hovel model and genetic algorithms
摘要： In this paper, a quick and accurate method for extraction of the minority carrier transport properties of p-n or n-p junction solar cells, such as diffusion lengths and surface recombination velocities, is presented. The knowledge of these parameters is essential to investigate factors that limit the performance of photovoltaic devices. The proposed method, based on genetic algorithms and the analytical Hovel model, is used to fit the external quantum efficiency (EQE) curves of solar cells with different emitter thicknesses. As a demonstrative example of application of the procedure carried out in this work, theoretical and experimental EQE curves of n-p GaAs solar cells under the standard AM1.5G spectrum have been used in order to extract the desired parameters. Errors less than 2.4% have been obtained, which shows the ability of the developed tool. An analysis of the total number of iterations is presented. Results obtained can be used to improve the design, optimization and manufacturing process of high efficiency photovoltaic devices.
关键词： diffusion length,surface recombination velocity,Hovel model and genetic algorithms,solar cells
更新于2025-09-23 15:19:57
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Cesium Lead Bromide Quantum Dot Light-Emitting Field-Effect Transistors
摘要： Solution processible perovskite quantum dots are considered as promising optical materials for light emitting optoelectronics. The light-emitting field-effect transistors that can be operated under relatively lower potential with an efficient energy conversion efficiency have yet to be realized with the perovskite quantum dot. Here, we present the CsPbBr3 quantum dot-based light-emitting field-effect transistor (LEFET). Surprisingly, unipolar transport characteristics with strong electroluminescence was observed at the interface of the CsPbBr3 QD-LEFET along with the exceptionally wide recombination zone of 80 μm, an order of magnitude larger than that of organic/polymer light-emitting field-effect transistors. Based on the systematic analysis for the electroluminescence of the CsPbBr3 NC-LEFET, we revealed that the increased diffusion length determined by the majority carrier mobility and the lifetime well explains the remarkably wide recombination zone. Furthermore, it was found that the energy-level matching and transport geometry of the hetero-structure also determine the charge distribution and recombination, substantially affecting the performance of the CsPbBr3 QD LEFET.
关键词： Organic/inorganic hybrid field-effect-transistor,Light emitting field-effect-transistor,Wide recombination zone,Diffusion length,CsPbBr3 quantum dots
更新于2025-09-23 15:19:57
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[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Mapping of Bulk Diffusion Length and Effective Back Surface Recombination Velocity in Silicon Solar Cells
摘要： Mapping of diffusion length (L) in the bulk region and effective back surface recombination velocity (SRV) in Al-BSF and PERC Si solar cells has been carried out by utilizing the spectral response (SR) at desired wavelengths. Light beam induced current (LBIC) technique was used to generate the maps of SR and re?ectivity (R) on cell area (6”x6”). MATLAB tool was used to convert the spatial maps of SR and R into L and SRV. We found that (i) the distribution of L in multi-crystalline cells varied from grain to grain in wide range (150-600 μm) while in mono-crystalline cells, it varied in rather narrow range (450-600 μm) ; (ii) the values of SRV for PERC cells (120-250 cm/sec for mono-crystalline and 100-250 cm/sec for multi-crystalline) and Al-BSF cells (320-400 cm/sec for mono-crystalline and 250-350 cm/sec for multi-crystalline) differ by considerable magnitude due to passivation quality at back side. Three multi-crystalline Al-BSF Si solar cells of cell ef?ciencies 17.6%, 17.9% and 18.1% were investigated with the proposed methodology and demonstrated that the ef?ciency de?cit is primarily due to defects present in bulk material and poor back surface passivation.
关键词： Light beam induced current,Surface recombination velocity,Diffusion length,Si solar cells
更新于2025-09-23 15:19:57
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The effects of air, oxygen and water exposure on the sub-bandgap absorption, the electronic conductivity and the ambipolar diffusion length in highly crystalline microcrystalline silicon films for photovoltaic applications
摘要： Reversible and irreversible changes due to long term air and short term de-ionized water (DIW) or pure oxygen exposure were investigated in about 1 μm thick hydrogenated microcrystalline silicon (μc-Si:H) films deposited on rough glass substrates, thereby comparing highly crystalline with compact material. Time and temperature dependent dark conductivity, steady-state photoconductivity, the steady-state photocarrier grating and dual-beam photoconductivity methods have been used to study the effects. Standard measurement procedures defined previously have been carefully applied to record the changes after different treatments using the steady-state methods under light. After long term air exposure of highly crystalline μc-Si:H films, a thermal annealing step leads to an increase in dark conductivity (σD) and steady-state photoconductivity (σph) as well as to a significant increase in the sub-bandgap absorption. These effects are likely due to a reversible recovery from surface adsorbents in a porous microstructure after air exposure resulting in surface charge and Fermi level shifts in agreement with earlier results. Compact μc-Si:H films showed only marginal effects upon an annealing after long term air exposure suggesting much reduced susceptibility to surface adsorbent induced by Fermi level shifts. Five hours exposure to de-ionized water at 80 °C caused more than an order of magnitude increase in σD and σph and a substantial decrease in the sub-bandgap absorption spectrum in highly crystalline as well as in compact μc-Si:H films. In addition, minority carrier diffusion lengths measured by the steady-state photocarrier grating method improved significantly. The changes after exposure to water were not reversible upon our standard annealing procedure. Exposure to high purity oxygen gas at 150 °C resulted in similar effects like the exposure to DIW. Also here the changes in material properties were not reversible upon annealing. Results are discussed in terms of adsorption and chemical reactions on surfaces in the porous highly crystalline material versus the materials with more compact structures. Results are compared to earlier observations and consequences for device application will be indicated.
关键词： microcrystalline silicon,electronic conductivity,sub-bandgap absorption,photovoltaic applications,ambipolar diffusion length
更新于2025-09-19 17:13:59
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Enhanced efficiency and stability of perovskite solar cells by 2D perovskite vapor-assisted interface optimization
摘要： Organic-inorganic perovskites solar cells (PSCs) have attracted great attention due to their rapid progress in power conversion efficiency (PCE). However, there is still an enormous challenge to achieve both high efficiency and stability devices as the decomposition of perovskite materials under humid and light conditions. Herein, we demonstrate that high efficiency and stability of PSCs can be obtained by the reaction of three-dimensional (3D) perovskite with 1, 4-butanediamine iodide (BEAI2) vapor. The incorporation of BEAI2 intensively promotes the crystallization of perovskite film with large grain size (~500 nm). Further characterization reveals that the post-treatment perovskite film delivered low interface trap density with long carrier lifetime (> 200 ns), long carrier diffusion length (> 600 nm) and large carrier mobility (> 1.5 cm2 V-1 S-1). Solar cells employing such post-treatment films demonstrated 19.58% PCE without hysteresis. Moreover, the post-treatment devices can retain over 90% original efficiencies stored under ambient atmospheric conditions and exhibit better stability under 85 °C and continuous illumination as a two-dimensional (2D) perovskite thin layer is formed on the surface/or at the grain boundaries of 3D perovskite. This study offers an effective way to obtain PSCs with high efficiency and stability.
关键词： Mobility,Post-treatment,Perovskite solar cells,2D/3D perovskite,Carrier diffusion length
更新于2025-09-19 17:13:59
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Extraordinarily long diffusion length in PM6:Y6 organic solar cells
摘要： The PM6:Y6 bulk-heterojunction (BHJ) blend system achieves high short-circuit current (JSC) values in thick photovoltaic junctions. Here we analyse these solar cells to understand the observed independence of the short-circuit current upon photoactive layer thickness. We employ a range of optoelectronic measurements and analyses, including Mott-Schottky analysis, CELIV, photoinduced absorption spectroscopy, Kelvin-probe potential measurements and simulations, to conclude that, for the device series studied, the invariant photocurrent for devices with different active layer thicknesses is associated with the Y6 diffusion length exceeding 300 nm. This is despite an unintentional doping that occurs in PM6 and the associated space-charge effect, which is expected to be even more profound upon photogeneration. This extraordinarily long diffusion length - which is an order of magnitude larger than typical values for organics - dominates transport in the flat-band region of thick junctions. Our work suggests that the performance of the doped PM6:Y6 organic solar cells resembles that of inorganic devices with diffusion transport playing a pivotal role. Ultimately, this is expected to be a key requirement for the fabrication of efficient, high-photocurrent, thick organic solar cells.
关键词： bulk-heterojunction,photovoltaic junctions,organic solar cells,diffusion length,PM6:Y6
更新于2025-09-19 17:13:59
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Optimized Analysis of Back-Contact Perovskite Solar Cells Architectures
摘要： The perovskite solar cells with back-contact structure was reported recently that its carriers have a good diffusion length of 12μm, which was considered as an innovational way to improve the cell's power conversion efficiency (PCE). Based on this reported experiment, the diffusion and drift of photogenerated carriers of the back-contact structure perovskite solar cell are calculated here detailly. Furthermore, the influence of carrier diffusion length, geometric scale, position of back-contact buried gate, and structure of the cell on performance is analyzed. The results showed that the PCE of a modified back-contact perovskite solar cell is superior to that of reported back-contact structure cell and traditional p-i-n structure cell under the same material parameters. It shows that the modified back-contact perovskite solar cells with optimized parameters achieved PCE of 28.27%.
关键词： Perovskite,Back-contact,Diffusion length,Solar cell
更新于2025-09-19 17:13:59