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Interface charge engineering in down-scaled AlGaN (<6a??nm)/GaN heterostructure for fabrication of GaN-based power HEMTs and MIS-HEMTs
摘要： The physical mechanism for recovery of 2D electron gas (2DEG) in down-scaled AlGaN/GaN heterostructures with SiNx layers grown by low-pressure chemical vapor deposition (LPCVD) was investigated by means of Hall-effect characterization, scanning Kelvin probe microscopy (SKPM), and self-consistent Poisson–Schr€odinger calculations. Observations using SKPM show that the surface potential of the AlGaN/GaN heterostructure remained nearly unchanged ((cid:2)1.08 eV) as the thickness of the AlGaN barrier was reduced from 18.5 to 5.5 nm and likely originated from the surface pinning effect. This led to a signi?cant depletion of 2DEG from 9.60 (cid:3) 1012 to 1.53 (cid:3) 1012 cm(cid:4)2, as determined by Hall measurements, toward a normally OFF 2DEG channel. Based on a consistent solution of the Schr€odinger–Poisson equations and analytical simulations, approximately 3.50 (cid:3) 1013 cm(cid:4)2 of positive ?xed charges were con?rmed to be induced by a 20-nm LPCVD-SiNx passivation over the AlGaN/GaN heterostructures. The interface charge exerted a strong modulation of band bending in the down-scaled AlGaN/GaN heterostructure, contributing to the ef?cient recovery of 2DEG charge density ((cid:2)1.63 (cid:3) 1013 cm(cid:4)2). E-mode ultrathin-barrier AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors with a low ON-resistance (RON), high ON/OFF current ratio, and steep subthreshold slope were implemented using LPCVD-SiNx passivation.
关键词： AlGaN/GaN heterostructure,power HEMTs,LPCVD-SiNx passivation,2D electron gas,MIS-HEMTs,interface charge engineering
更新于2025-09-23 15:19:57
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Surface Engineering of Alla??Inorganic Perovskite Quantum Dots with Quasi Corea??Shell Technique for Higha??Performance Photodetectors
摘要： All-inorganic lead halide perovskites with good surface morphology show substantial prospect for optoelectronic devices. However, the anion exchange of coordinated alkylamine ligands (e.g., oleic acid and oleylamine) can detach ligands and induce more interface trap sites, subsequently to reduce device performance. In this paper, therefore, a simple solution-processed route is presented to synthesize quasi coreshell CsPbBr3formamidinium iodide (FAI = CH(NH2)2I) colloidal quantum dots (CQDs), and then it is applied as the active layer for photodetectors by finely controlling the ligands exchange. The presence of FAI = CH(NH2)2I on CsPbBr3 is confirmed by Fourier transform infrared spectroscopy. As a result, the photodetector ITO/ZnO (100 nm)/CsPbBr3 (150 nm)/Au show an enhanced specific detectivity over 1013 Jones with a responsivity of 19 A W1 under 3 mW cm2 405 nm illumination at 1.5 V. The experimental data show that the enhanced device performance is due to the improved crystallinity and less surface defects of CsPbBr3 CQDs, as the result of less alkylamine ligands is detached during its FAI passivation, thus the charge carriers’ mobility of the film is improved. Therefore, it provides a promising way for high-performance solution-processed all-inorganic CsPbBr3 based optoelectronic devices.
关键词： CsPbBr3 perovskite nanocrystals,solution-processed,surface passivation,recombination process
更新于2025-09-23 15:19:57
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A New Strategy for Increasing the Efficiency of Inverted Perovskite Solar Cells to More than 21%: Higha??Humidity Induced Selfa??Passivation of Perovskite Films
摘要： The performance of perovskite solar cells (PSCs) are known to be extremely sensitive to humidity in the preparation environment. However, the main mechanism by which the moisture influences the quality of the perovskite film and the device performance is not yet completely revealed. In this work, we established a new strategy to obtain inverted PSCs with remarkable high VOC by including a high-humidity treatment and sufficient DMSO-atmosphere annealing in the preparation process. We found that the lattice distortion on the surface of perovskite grains caused by the high-humidity treatment played a key role in the self-passivation of perovskite. Inverted (p-i-n) PSCs based on the self-passivated perovskite films showed effective suppression of non-radiative recombination, which increased the device VOC to 1.17 V and achieved the highest efficiency of 21.38 %. It is expected that the findings of this work shed more light on the currently proposed mechanism governing the action of moisture on the performance of the PSCs.
关键词： Self-passivation,High open-circuit voltage,Perovskite solar cells,High-humidity,Grain boundaries
更新于2025-09-23 15:19:57
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A facile surface passivation method for efficient inorganic CsPbI2Br perovskite solar cells with efficiencies over 15%; é??????????oCsPbI2Bré??é??????¤aé?3è????μ?±?è?¨é?￠é????????????????1?3?;
摘要： Recently, perovskite solar cells (PVSCs) based on CsPbI2Br have attracted increasing attention owing to their good balance between efficiency and stability. Solution-processed CsPbI2Br perovskites usually contain various defects which need passivation for PVSCs with high-performance as well as good stability. Since the degradation of perovskite films usually begins at the grain boundaries, here we report a facile defect passivation strategy by spin-coating a KF solution on the CsPbI2Br perovskite surface. The deposited KF salt mostly locates at the grain boundaries of the perovskite surface, resulting in PVSCs with improved stability. Both steady-state and time-resolved photoluminescence results suggest that the defects of perovskite were significantly passivated by KF treatment. Consequently, the best-performance PVSC based on CsPbI2Br with KF treatment shows an enhanced power conversion efficiency (PCE) of 15.01% with a larger open circuit voltage (VOC) of 1.26 V in comparison with the pristine CsPbI2Br-based counterpart which exhibits an inferior PCE of 14.14% with a VOC of 1.18 V.
关键词： grain boundary,perovskites,defect,energy conversion,fluorides,passivation
更新于2025-09-23 15:19:57
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Naphthalene imide dimer as interface engineering material: An efficient strategy for achieving high-performance perovskite solar cells
摘要： How to design and synthesize interfacial engineered materials that have efficient surface passivation and electron extraction properties is an important problem in the field of optoelectronic materials. Herein, a simple naphthalene imide dimer, namely 2FBT2NDI, is developed by Stille coupling reaction with a high yield, and it is used as interface engineering for inverted perovskite solar cells (PSC). Owing to the existence of intermolecular interactions between MAPbI3 and the 2FBT2NDI layer, the introduction of the interfacial layer can passivate the surface defects of perovskite film and improve interface contact. In addition, 2FBT2NDI exhibits suitable energy levels and high electron mobility because of its large linear conjugated skeleton containing two fluorine atoms, which are beneficial for electron extraction for efficient PSCs. Employing 2FBT2NDI as an interfacial layer, inverted PSCs show a maximum power conversion efficiency of 20.1%, which is over 14% higher than that of the control devices without interfacial layer (17.1%). These results highlight that the naphthalene imide dimer can potentially be used as a commercializable interfacial material for achieving high-performance PSCs.
关键词： electron extraction,perovskite solar cell,naphthalene imide,surface passivation,interface engineering
更新于2025-09-23 15:19:57
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Thermally Stable Perovskite Solar Cells with Efficiency over 21% via Bifunctional Additive
摘要： The rapid improvements in performance of organic-inorganic perovskite solar cells has been astonishing but its commercialized production requires further achievements on device stability and efficiency. Herein, we introduce a bifunctional additive, biuret, with multiple Lewis base groups to regulate the crystallization process of perovskite crystals and passivate the defects at grain boundaries. Compared with the control, methylammonium lead iodide (MAPbI3), films processed with biuret exhibit increased grain size, reduced trap states density, and more uniform local photoluminescence. The addition of biuret leads to suppressed trap-assisted nonradiative recombination and an efficiency improvement from 18.26% to 21.16%, which is among the highest efficiency for MAPbI3 solar cells with the mesoscopic structure. Meanwhile, as biuret interacts with uncoordinated Pb2+ and iodide from the iodoplumbate complex on two adjacent perovskite grains, the thermal durability of MAPbI3 film is enhanced due to the crosslink through chemical bonding. Under 85°C annealing in nitrogen, the biuret-modified device preserves 94% of its initial efficiency after 12 days while the control cells lose more than half the efficiency.
关键词： crystallization,defect passivation,bifunctional additive,perovskite solar cell,stability
更新于2025-09-23 15:19:57
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Bifunctional effects of trichloro(octyl)silane modification on the performance and stability of perovskite solar cell via microscopic characterization techniques
摘要： Passivation by small organic compounds can reduce the trap density and enhance humidity and illumination stability of perovskite solar cells (PSCs). However, the small molecule passivated on the perovskite film cannot endure harsh heat stress. Herein, we find that the trichloro(octyl)silane (TC-silane) is an excellent candidate to modify the perovskite surface and grain boundary nondestructively through the formation of heat-resistive silicone layer, leading to comprehensive improvement of efficiency and stability with low cost as well as facile fabrication. The silane is a type of solvent and can be upscaled by solution process in the device. TC- silicone can crosslink the grain boundaries through hydrolytic condensation. The crosslinking silicone can resist the moisture and heat stresses to enhance the stability. Besides, micro-photoluminescence reveals that TC-silane treatment can passivate the perovskite film and enhance the optoelectronic properties through chloride replenishment during releasing hydrogen chloride molecule in the hydrolytic reaction. By utilizing Kevin probe force microscopy, we further uncover that TC-silane forms a dipole layer to facilitate the charge separation. TC-silane passivated PSCs delivers a champion efficiency of 20.03% and remains 80% of initial efficiency for more than 800 h at 70-80% relative humidity in air and for about 80 h under 85 oC thermal stress without encapsulation.
关键词： perovskite solar cell,microscopic characterization,silane passivation,stability,bifunctional effect
更新于2025-09-23 15:19:57
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Ammonium acetate passivated CsPbI3 perovskite nanocrystals for efficient red light-emitting diodes
摘要： Lead halide perovskite nanocrystals (PNCs) have very recently emerged as promising emitters for their superior optoelectronic properties. However, the defects in perovskite itself make it susceptible to the external environment and internal ion migration, resulting in low photoluminescence quantum yield (PLQY) and poor device efficiency. Herein, we developed a method to reduce the surface defects of PNCs by introducing ammonium acetate in the synthesis of CsPbI3 PNCs. The addition of ammonium acetate can effectively eliminate undesired surface metallic lead cations and dangling bonds, resulting in an enhanced PLQY and stability. The passivated PNCs have an overall up-shift energy level, demonstrating better hole injection efficiency. As a result, the red light-emitting diodes (LEDs) fabricated with the passivated CsPbI3 PNCs achieved an optimal EQE of 10.6% and a maximum brightness of 981 cd/m2, which are 3.1 and 2.4 times that of unpassivated PNCs based devices, respectively.
关键词： CsPbI3 nanocrystals,ammonium acetate,defect passivation,photoluminescence quantum yield,light-emitting diodes
更新于2025-09-23 15:19:57
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Electron and proton irradiation effect on the minority carrier lifetime in SiC passivated p-doped Ge wafers for space photovoltaics
摘要： We report on the effect of electron and proton irradiation on effective minority carrier lifetimes (τeff) in p-type Ge wafers. Minority carrier lifetimes are assessed using the microwave-detected photoconductance decay (μW-PCD) method. We examine the dependence of τeff on the p-type doping level and on electron and proton radiation fluences at 1 MeV. The measured τeff before and after irradiation are used to estimate the minority carriers’ diffusion lengths, which is an important parameter for solar cell operation. We observe τeff ranging from ~50 to 230 μs for Ge doping levels between 1 × 1017 and 1 × 1016 at.cm-3, corresponding to diffusion lengths of ~500–1400 μm. A separation of τeff in Ge bulk lifetime and surface recombination velocity is conducted by irradiating Ge lifetime samples of different thicknesses. The possible radiation-induced defects are discussed on the basis of literature.
关键词： Space photovoltaics,Minority carrier lifetime,Germanium,Surface passivation,Irradiation
更新于2025-09-23 15:19:57
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Amphoteric imidazole doping induced large-grained perovskite with reduced defect density for high performance inverted solar cells
摘要： Intrinsic defect density in polycrystalline halide perovskite films are required to be low enough to suppress charge recombination loss for improvement in performance of perovskite solar cells (PeSCs). In this paper, we propose the use of amphoteric imidazole to achieve high crystalline quality of CH3NH3PbI3 perovskite absorption layer. The imidazole additive plays a synergistic role in controlling the perovskite crystal growth for large grain size and passivating the uncoordinated ions (e.g., Pb2+) defects, resulting in improved carrier transport/lifetime and suppressed non-radiative recombination. The champion power conversion efficiency (PCE) of PeSCs with imidazole is improved to 16.88%, from the control device with a PCE value of 14.65%. Besides, the stability of imidazole modified perovskite films is further improved by limiting ion immigration at grain boundaries against moisture and heat stresses. The findings pave an avenue for synergistically modulating crystallization and healing defect in perovskite to achieve efficient and stable solar cells.
关键词： Defect passivation,CH3NH3PbI3,Grain boundary,Inverted solar cell,Non-radiative recombination
更新于2025-09-23 15:19:57