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Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices
摘要： One source of instability in perovskite solar cells (PSCs) is interfacial defects, particularly those that exist between the perovskite and the hole transport layer (HTL). We demonstrate that thermally evaporated dopant-free tetracene (120 nm) on top of the perovskite layer, capped with a lithium-doped Spiro-OMeTAD layer (200 nm) and top gold electrode, offers an excellent hole-extracting stack with minimal interfacial defect levels. For a perovskite layer interfaced between these graded HTLs and a mesoporous TiO2 electron-extracting layer, its photoluminescence yield reaches 15% compared to 5% for the perovskite layer interfaced between TiO2 and Spiro-OMeTAD alone. For PSCs with graded HTL structure, we demonstrate efficiency of up to 21.6% and an extended power output of over 550 hours of continuous illumination at AM1.5G, retaining more than 90% of the initial performance and thus validating our approach. Our findings represent a breakthrough in the construction of stable PSCs with minimized nonradiative losses.
关键词： perovskite solar cells,stability,charge extraction,photoluminescence,hole transport layers,graded doping
更新于2025-11-14 15:25:21
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Maze-Like Halide Perovskite Films for Efficient Electron Transport Layer-Free Perovskite Solar Cells
摘要： Perovskite solar cells (PSCs) without an electron transport layer (ETL) exhibit fascinating advantages such as simplified configuration, low cost, and facile fabrication process. However, the performance of ETL-free PSCs has been hampered by severe charge carrier recombination induced either by current leakage (insufficient perovskite film coverage) or inferior charge extraction. Herein, an additive-assisted morphological engineering strategy is used to construct an intriguing bilayer perovskite film featuring a dense bottom layer and a maze-like top layer. Such maze-like perovskite films enable the construction of ETL-free PSCs with a PCE of 18.5% and negligible hysteresis, which can be attributed to the higher crystallinity and superior light-harvesting capability of the resultant perovskite film, as well as facilitated hole extraction at the hole transport layer (HTL)/perovskite interface. This work provides a simple approach to modify the perovskite film morphology and demonstrates the correlation between facilitated charge-carrier extraction and high-performance ETL-free perovskite photovoltaics.
关键词： light harvesting,morphological engineering,additives,perovskite solar cells,charge extraction
更新于2025-10-22 19:40:53
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Understanding Temperature-Dependent Charge Extraction and Trapping in Perovskite Solar Cells
摘要： Understanding the factors that limit the performance of perovskite solar cells (PSCs) can be enriched by detailed temperature (T)-dependent studies. Based on p-i-n type PSCs with prototype methylammonium lead triiodide (MAPbI3) perovskite absorbers, T-dependent photovoltaic properties are explored and negative T-coefficients for the three device parameters (VOC, JSC, and FF) are observed within a wide low T-range, leading to a maximum power conversion efficiency (PCE) of 21.4% with an impressive fill factor (FF) approaching 82% at 220 K. These T-behaviors are explained by the enhanced interfacial charge transfer, reduced charge trapping with suppressed nonradiative recombination and narrowed optical bandgap at lower T. By comparing the T-dependent device behaviors based on MAPbI3 devices containing a PASP passivation layer, enhanced PCE at room temperature is observed but different tendencies showing attenuating T-dependencies of JSC and FF, which eventually leads to nearly T-invariable PCEs. These results indicate that charge extraction with the utilized all-organic charge transporting layers is not a limiting factor for low-T device operation, meanwhile the trap passivation layer of choice can play a role in the T-dependent photovoltaic properties and thus needs to be considered for PSCs operating in a temperature-variable environment.
关键词： temperature dependence,charge trapping,recombination,charge extraction,passivation layer
更新于2025-09-23 15:21:01
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Vertically aligned 2D/3D Pb-Sn perovskites with enhanced charge extraction and suppressed phase segregation for efficient printable solar cells
摘要： The concept of mixed 2D/3D heterostructures has emerged as an effective method in improving the stability of lead halide perovskite solar cells (PSCs), which is, however, rarely reported in lead-tin (Pb-Sn) mixed perovskite devices. Here, we report a scalable process for depositing mixed 2D/3D Pb-Sn perovskite solar cells that deliver remarkably enhanced efficiency and stability compared to their 3D counterparts. The incorporation of a small amount (3.75%) of an organic cation 2-(4-fluorophenyl)ethyl ammonium iodide (FPEAI) induces the growth of highly orientated Pb-Sn perovskite crystals perpendicularly aligned to the substrate. Moreover, for the first time, phase segregation is observed in pristine 3D Pb-Sn perovskite, which is suppressed due to the presence of the 2D perovskites. Accordingly, a high current density of 28.42 mA cm-2 is obtained due to markedly enhanced spectral response and charge extraction. Eventually, mixed 2D/3D Pb-Sn perovskite devices with a bandgap of 1.33 eV yield efficiencies as high as 17.51% and in parallel exhibit good stability.
关键词： 2D/3D heterostructures,charge extraction,Pb-Sn perovskite,solar cells,phase segregation
更新于2025-09-23 15:21:01
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Performance improvement of polymer solar cells with binary additives induced morphology optimization and interface modification simultaneously
摘要： Active layer morphology optimization and electrode buffer layer interface modification are commonly used strategies in improving the performance of polymer solar cells (PSCs). In this study, we prepared PTB7: PC71BM bulk heterojunction PSCs with 1,8-diiodooctane (DIO) and polyethylene glycol (PEG) additives, and studied the influence of binary additives on exciton dissociation, charge transport and charge extraction. DIO facilitates donor/acceptor phase separation for efficient exciton dissociation and charge transport. The migration of PEG from active layer to the PEDOT:PSS layer improves the crystallinity of PTB7, optimizes charge transport pathway, and enhances the conductivity of PEDOT:PSS layer. With the combined advantages of binary additives in active layer morphology optimization and anode buffer layer modification, the device exhibits a high short-circuit current density of 20.03 mA/cm2 and an improved power conversion efficiency. Binary additive provides a promising method to optimize active layer morphology and improve interfacial buffer layer of PSCs simultaneously.
关键词： Charge extraction,Charge transport,Binary additive,Polymer solar cells,Morphology,Interface modification
更新于2025-09-23 15:19:57
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Flexible Alla??Solutiona??Processed Organic Solar Cells with Higha??Performance Nonfullerene Active Layers
摘要： All-solution-processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low-cost and ubiquitous applications. However, it is still challenging to fabricate efficient all-solution-processed organic solar cells with a high-performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all-solution-processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (HXMoO3) between the active layer and the PEDOT:PSS. The dual functions of HXMoO3 include: 1) its deep Fermi level of ?5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the HXMoO3 composition during the synthesis is critical in obtaining processing orthogonality between HXMoO3 and the PEDOT:PSS. Flexible all-solution-processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm2, respectively.
关键词： nonfullerene organic solar cells,all-solution-processed,hydrogen molybdenum bronze,charge extraction,wetting
更新于2025-09-23 15:19:57
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Modification of NiO <sub/>x</sub> hole transport layer for acceleration of charge extraction in inverted perovskite solar cells
摘要： The modification of the inorganic hole transport layer has been an efficient method for optimizing the performance of inverted perovskite solar cells. In this work, we propose a facile modification of a compact NiOx film with NiOx nanoparticles and explore the effects on the charge carrier dynamic behaviors and photovoltaic performance of inverted perovskite devices. The modification of the NiOx hole transport layer can not only enlarge the surface area and infiltration ability, but also adjust the valence band maximum to well match that of perovskite. The photoluminescence results confirm the acceleration of the charge separation and transport at the NiOx/perovskite interface. The corresponding device possesses better photovoltaic parameters than the device based on control NiOx films. Moreover, the charge carrier transport/recombination dynamics are further systematically investigated by the measurements of time-resolved photoluminescence, transient photovoltage and transient photocurrent. Consequently, the results demonstrate that proper modification of NiOx can significantly enlarge interface area and improve the hole extraction capacity, thus efficiently promoting charge separation and inhibiting charge recombination, which leads to the enhancement of the device performances.
关键词： charge extraction,hole transport layer,NiOx,perovskite solar cells,photovoltaic performance
更新于2025-09-23 15:19:57
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Efficient Charge Transfer and Carrier Extraction in All-Polymer Solar Cells Using an Acceptor Filler
摘要： All-polymer solar cells (all-PSCs) exhibit considerably improved mechanical and thermal stability than their polymer-fullerene counterparts. Despite their advantages, the power conversion efficiencies of all-PSCs are still lower than those of polymer-fullerene PSCs. In this study, we demonstrate that introducing a small amount of fullerene or nonfullerene acceptors as filler into the photoactive layer of PBDBT:N2200 all-PSCs can enhance charge transport properties, thereby the device performance. An appreciable enhancement (~21%) in the power-conversion-efficiencies (PCEs) of all-PSCs, from 6.13% to 7.42%, is obtained when fullerene with the amount of 25 wt% PBDBT is added. The performance improvement is primary from the enhanced short circuit current density (Jsc), which can be attributed to the enhanced exciton dissociation, reduced charge recombination, and balanced charge transport in the prescence of the fullerene filler. Similar behavior is also observed when fullerene is replaced by ITIC molecules. Importantly, the fullerene filler shows a negiligible effect on the device storage and light-soaking stability. Therefore, all-PSCs incorporating a proper selected acceptor filler is an efficient way to improve device performance without sacrificing stability. We believe that our study can pave a useful approach for developing stable and high performance PSCs.
关键词： filler,all-polymer solar cell,charge transport,ternary,charge extraction
更新于2025-09-19 17:13:59
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Enhanced charge extraction in carbon-based all-inorganic CsPbBr3 perovskite solar cells by dual-function interface engineering
摘要： Carbon-based all-inorganic CsPbBr3 perovskite solar cells (PSCs) have attracted growing interests due to low cost and excellent tolerances toward moisture, temperature, oxygen and ultraviolet light. However, carrier recombination of CsPbBr3 film and large energy level differences at CsPbBr3/carbon interface are still the most crucial problem for further enhancement of power conversion efficiency. In the current study, an intermediate energy level at CsPbBr3/carbon interface and CsPbBr3 film passivation are employed by coating hexane solution of CsPbBrxI3-x nanocrystals (NCs) on the perovskite layer. Through systematic study on interfacial engineering, it is found that CsPbBrxI3-x NCs with tunable energy level can remarkably reduce energy loss and hexane under passivation treatment can enlarge perovskite grain size as well as reduce trap state density. A champion power conversion efficiency of 9.45% is achieved for CsPbI3 NCs tailored all-inorganic CsPbBr3 PSC in comparison with 5.26% for NCs-free device, with the unencapsulated carbon-based CsPbBr3 PSC exhibiting remarkable long-term stability over 900 h in 80% relative humidity air atmosphere at 25 °C. This work provides an effective approach to promote charge extraction and reduce defect states density as well as enhance the performance of PSCs.
关键词： CsPbBrxI3-x nanocrystals,Interface engineering,Charge extraction,Solvent treatment,All-inorganic CsPbBr3 perovskite solar cells
更新于2025-09-19 17:13:59
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Understanding the High Performance of over 15% Efficiency in Single‐Junction Bulk Heterojunction Organic Solar Cells
摘要： The highly efficient single-junction bulk-heterojunction (BHJ) PM6:Y6 system can achieve high open-circuit voltages (VOC) while maintaining exceptional fill-factor (FF) and short-circuit current (JSC) values. With a low energetic offset, the blend system is found to exhibit radiative and non-radiative recombination losses that are among the lower reported values in the literature. Recombination and extraction dynamic studies reveal that the device shows moderate non-geminate recombination coupled with exceptional extraction throughout the relevant operating conditions. Several surface and bulk characterization techniques are employed to understand the phase separation, long-range ordering, as well as donor:acceptor (D:A) inter- and intramolecular interactions at an atomic-level resolution. This is achieved using photo-conductive atomic force microscopy, grazing-incidence wide-angle X-ray scattering, and solid-state 19F magic-angle-spinning NMR spectroscopy. The synergy of multifaceted characterization and device physics is used to uncover key insights, for the first time, on the structure–property relationships of this high-performing BHJ blend. Detailed information about atomically resolved D:A interactions and packing reveals that the high performance of over 15% efficiency in this blend can be correlated to a beneficial morphology that allows high JSC and FF to be retained despite the low energetic offset.
关键词： organic photovoltaics,charge extraction,recombination,solid-state NMR,low voltage losses
更新于2025-09-19 17:13:59