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Revealing the compositional effect on the intrinsic long-term stability of perovskite solar cells
摘要： Understanding role of individual cation and halide components on the intrinsic long-term stability of perovskite solar cells (PSCs) is of great importance to pursue devices with high efficiency and superior long-term stability simultaneously. In this work, we report a low dopant content (1%) doping strategy to reveal the role of individual bromide and methylammoniun (MA) on the intrinsic operational stability of formamidinium lead iodide (FAPbI3-based) PSCs. This strategy enables us to tune the trap density of perovskite films while keep their apparent morphological and optical properties unchanged. Our results demonstrate that incorporation of MA into the FAPbI3-based PSCs is harmful to the long-term stability due to defect-induced degradation. And Br incorporation is beneficial to enhance the stability of FAPbI3-based PSCs via suppressing the trap density in the perovskite films. This work highlights the importance of defects management for improving the long-term operational stability of perovskite solar cells.
关键词： compositional effect,defects management,intrinsic stability,trap density,perovskite solar cells
更新于2025-09-23 15:21:01
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Oriented Crystallization of Mixeda??Cation Tin Halides for Highly Efficient and Stable Leada??Free Perovskite Solar Cells
摘要： As the most promising lead-free branch, tin halide perovskites suffer from the severe oxidation from Sn2+ to Sn4+, which results in the unsatisfactory conversion efficiency far from what they deserve. In this work, by facile incorporation of methylammonium bromide in composition engineering, formamidinium and methylammonium mixed cations tin halide perovskite films with ultra-highly oriented crystallization are synthesized with the preferential facet of (001), and that oxidation is suppressed with obviously declined trap density. MA+ ions are responsible for that impressive orientation while Br- ions account for their bandgap modulation. Depending on high quality of the optimal MA0.25FA0.75SnI2.75Br0.25 perovskite films, their device conversion efficiency surges to 9.31% in contrast to 5.02% of the control formamidinium tin triiodide perovskite (FASnI3) device, along with almost eliminated hysteresis. That also results in the outstanding device stability, maintaining above 80% of the initial efficiency after 300 h of light soaking while the control FASnI3 device fails within 120 h. This paper definitely paves a facile and effective way to develop high-efficiency tin halide perovskites solar cells, optoelectronic devices, and beyond.
关键词： trap density,methylammonium bromide,oriented crystallization,tin halide perovskites,divalent tin ions
更新于2025-09-23 15:21:01
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Enhanced device performance with passivation of the TiO <sub/>2</sub> surface using a carboxylic acid fullerene monolayer for a SnPb perovskite solar cell with a normal planar structure.
摘要： Research on tin-lead (SnPb) perovskite solar cells (PSCs) have gained popularity in recent years due to their low bandgap which could be applied to tandem solar cells. However, most of the work are based on inverted PSCs using PEDOT:PSS as the hole transport layer as the normal structure PSCs show lower efficiency. In this work, the reason behind the low efficiency of normal structure SnPb PSCs is elucidated and the method to overcome the problem has been attempted through surface passivation. In the case of normal PSCs, at the interface between titania layer and SnPb perovskite there are many carrier traps observed originating from Ti-O-Sn bonds. In order to avoid the direct contact between titania and SnPb perovskite layer, the titania surface is passivated with carboxylic acid C60 resulting in efficiency increase from 5.14 % to 7.91 %. This will provide a direction of enhancing the efficiency of normal structure SnPb PSCs through heterojunction engineering.
关键词： passivation,Perovskite solar cells,Tin,titania,Lead,trap density,interface
更新于2025-09-23 15:19:57
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Highly Reproducible and Efficient FASnI <sub/>3</sub> Perovskite Solar Cells Fabricated with Volatilizable Reducing Solvent
摘要： Lead-free tin halide perovskite solar cells (PSCs) have attracted great attention because of their low toxicity, ideal band gap, and high carrier mobilities. However, the efficiency and reproducibility of tin halide PSCs has been limited because of the facile oxidation of Sn2+ to Sn4+. Herein, liquid formic acid (LFA) was introduced as a reducing solvent in the FASnI3 (FA: formamidinium) perovskite precursor solution. Unlike solid reducing additives, the LFA solvent is volatile, so no residual LFA remained in the FASnI3 perovskite film. Use of the LFA solvent resulted in production of the FASnI3 perovskite film with high crystallinity, low Sn4+ content, reduced background doping, and low electronic trap density. As a result, an efficiency of over 10% was obtained for lead-free tin halide PSCs with improved reproducibility.
关键词： tin,Lead-free,oxidation,trap density,standard reduction potential
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - 2D Simulations of the NS-Laser Shock Peening
摘要： We report on the impact of H2 high-pressure annealing (HPA) onto In0.7Ga0.3As MOSCAPs and quantum-well (QW) MOSFETs with Al2O3/HfO2 gate-stack. After HPA with process condition of 300 °C, H2 ambient and pressure of 20 atm, we observed notable improvements of the capacitance–voltage (CV) characteristics in InGaAs MOSCAPs with Al2O3/HfO2 gate-stack, such as reduction of equivalent-oxide-thickness and less frequency dispersion in the accumulation region. There was 20% improvement of the interfacial trap density ( Dit). Then, we incorporated the HPA process into the fabrication of sub-100-nm In0.7Ga0.3As QW MOSFETs, to investigate the impact of HPA process. After HPA process, the device with L g = 50 nm exhibits improved subthreshold-swing (SS) = 105 mV/decade, in comparison with SS = 130 mV/decade for the reference device without HPA process. Finally, we carried out reliability assessment under a constant-voltage-stress (CVS), and it turns out that the HPA process was effective in mitigating a shift of threshold voltage ((cid:2)VT ) during the CVS. These are attributed to the effective passivation of oxide traps in the high-k dielectric layer and interfacial traps, after HPA process in the H2 ambient.
关键词： interfacial trap density (Dit),subthreshold-swing (SS),high-pressure annealing,atomic layer deposition (ALD),InGaAs MOSFET
更新于2025-09-19 17:13:59
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Charge Transport and Photovoltaic Properties of Conjugated Polymer PTB7:PC71BM Based Solar Cells
摘要： We investigate the charge transport in organic solar cells based on PTB7:PC71BM by measuring the J (V) characteristics at different temperatures (140–325 K). In dark, two models dominate the transport. The Ohmic law overcomes for the low applied low voltages, and for high voltages the trapped charge limited current governs the transport with an average total concentration of trap around 5.62 × 1015 cm?3. At higher voltages there is evidence of an electrode-to-bulk limited transition, with conductivity dominated by the Poole–Frenkel effect. The photovoltaic conversion properties of the junction were also studied by carrying out the J–V measurements at room temperature under illumination of 100 mW/cm2 and a power conversion efficiency of 6.49% has been achieved. the other cell parameters, the short-circuit current density JSC, the open circuit voltage VOC and de fill factor FF, were found to be 12.87 mA/cm2, 0.77 V and 0.65 respectively. These values were compared with other organic solar cells found in literature.
关键词： Charge transport,Photovoltaics,Organic materials,Trap density
更新于2025-09-19 17:13:59
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Solvent engineering of LiTFSI towards high-efficiency planar perovskite solar cells
摘要： The performance and stability of perovskite solar cell (PSC) are inseparable from the quality of perovskite film, and the solvent engineering is being seemed as an effective strategy to enhance the properties of perovskite. Acetonitrile (ACN) is often used as a solvent to dissolve bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), but ACN can corrode the perovskite film, which hinders the promotion of PSC efficiency and durability. Herein, a solvent engineering approach is implemented to search for suitable alternatives for ACN to abate the degradation of the perovskite films. The results demonstrate that isopropanol (IPA) with smaller polarity can effectively dissolve LiTFSI and slow down the degradation of the perovskite layer compared with ACN, which can result in the reduction of defects as well as the nonradiative recombination. Consequently, the devices using LiTFSI/IPA as additive achieve superior power conversion efficiencies (PCEs) with relatively less hysteresis effects and get a champion PCE of 19.43%, while the device using LiTFSI/ACN gets an inferior PCE of 17.12%.
关键词： Trap density,Nonradiative recombination,Solvent engineering,Isopropanol,Perovskite solar cells
更新于2025-09-16 10:30:52
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Tuning methylammonium iodide amount in organolead halide perovskite materials by post-treatment for high-efficiency solar cells
摘要： In this study, the composition of organic-inorganic perovskite materials is tuned by methylammonium iodide (MAI) post-treatment for high photovoltaic performance. By spin-coating MAI solutions of different concentrations, the amounts of PbI2 and MAI in perovskite layers are tuned. In perovskites, the removal of PbI2 through a reaction with MAI decreases the hysteresis in photocurrent density-voltage curves. Further, by treating perovskites with a high-concentration MAI solution, the excess MAI is incorporated into the perovskites. These perovskites with excess MAI show better power conversion efficiencies (of up to 20.7%) than perovskites with excess PbI2, because of the decrease in trap density. Since the present post-treatment can control perovskite composition without affecting the morphology and crystallinity of the perovskite crystals, this technique would be a useful tool to improve the photovoltaic performance of perovskite solar cells.
关键词： ion composition,performance enhancement,perovskite solar cells,trap density,surface treatment
更新于2025-09-12 10:27:22
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Well-grown low-defect MAPbI3–xClx films for perovskite solar cells with over 20% efficiency fabricated under controlled ambient humidity conditions
摘要： The conventional MAI [(CH3NH3I (MAI)):PbI2:PbCl2= 3 : 0 : 1 [abbreviated as (3:0:1)]] precursor solution is known to result in CH3NH3PbI3–xClx films with large grain sizes when processed in an inert atmosphere, but it gives non-uniform perovskite films containing lots of voids and cracks when processed in ambient air. Furthermore, a dramatically longer annealing time (usually 100 min) is required for these films (3:0:1) due to the slow formation of the MAPbI3 phase via MACl loss, which is not conducive to perovskite film formation under ambient conditions due to perovskite degradation upon long exposure to moisture. Pure MAPbI3 films can be formed very rapidly from (1:1:0) (MAI:PbI2:PbCl2= 1 : 1 : 0) solution within a short annealing time, but they show small grain sizes and poor film quality. This work demonstrated that a fractional substitution of PbI2 with PbCl2 in the ([MAI]:[PbI2]= 1 : 1) precursor solution has a significant influence on film morphology and quality in terms of crystallization rate, grain size, crystallinity, and trap density of the formed perovskite film. Perovskite films can be formed with 5-min annealing at 100 °C from the precursor (MAI: PbI2:PbCl2= 1: 0.8 : 0.2) processed in ambient air (humidity, 20% RH), exhibiting more uniform, increased grain size and higher film quality with reduced trap densities compared to film (1:1:0), thus leading to significantly improved power conversion efficiency (PCE), from 16.7% for perovskite solar cells (PrSCs) based on film (1:1:0) to 20.04% for the cell based on film (1:0.8:0.2). Further, the effects of R (R= [MAI]/[PbI2+PbCl2]) on morphology, hole mobility, carrier lifetime and efficiency of PrSCs were systematically and thoroughly investigated. This study found that MAPbI3–xClx at R=1 can enable the highest hole mobility and longest carrier lifetime, thus giving the best performance at R=1.
关键词： mixed halide perovskite solar cells,lead chloride,grain size,trap density,crystal growth intermediates
更新于2025-09-12 10:27:22
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Atomic-layer deposition of crystalline BeO on SiC
摘要： For the ?rst time, an epitaxial beryllium oxide (BeO) ?lm was grown on 4H silicon carbide (4H-SiC) by atomic layer deposition (ALD) at a low temperature of 250 °C. The BeO ?lm had a large lattice mismatch with the substrate (> 7–8%), but it was successfully grown to a single crystal by domain-matching epitaxy (DME). The bandgap energy, dielectric constant, and thermal conductivity properties of crystalline BeO are suitable for power transistors that require low leakage currents and fast heat dissipation in high electric ?elds. Physical characterization con?rmed the single-crystalline BeO (0 0 2). Raman analysis showed that the E1 and A1 phonon modes of ALD BeO were intermixed with the E2 and A1 phonon modes of SiC, resulting in a signi?cant increase in phonon intensity. After heat treatment at a high temperature, a small amount of SiO2 interfacial oxide was formed but the stoichiometry of BeO was maintained. From the capacitance-voltage (C-V) curves, we obtained a dielectric constant of 6.9 and calculated a low interface trap density of 6 × 1010 cm?2·eV?1 using the Terman method at Ec-Et = 0.6 eV. The high bandgap, thermal conductivity, and excellent crystallinity reduced the dangling bonds at the interface of BeO-on-SiC.
关键词： Interface trap density,Atomic layer deposition,Domain matching epitaxy,Silicon carbide,Beryllium oxide
更新于2025-09-11 14:15:04