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Enabling low voltage losses and high photocurrent in fullerene-free organic photovoltaics
摘要： Despite significant development recently, improving the power conversion efficiency of organic photovoltaics (OPVs) is still an ongoing challenge to overcome. One of the prerequisites to achieving this goal is to enable efficient charge separation and small voltage losses at the same time. In this work, a facile synthetic strategy is reported, where optoelectronic properties are delicately tuned by the introduction of electron-deficient-core-based fused structure into non-fullerene acceptors. Both devices exhibited a low voltage loss of 0.57 V and high short-circuit current density of 22.0 mA cm?2, resulting in high power conversion efficiencies of over 13.4%. These unconventional electron-deficient-core-based non-fullerene acceptors with near-infrared absorption lead to low non-radiative recombination losses in the resulting organic photovoltaics, contributing to a certified high power conversion efficiency of 12.6%.
关键词： non-fullerene acceptors,power conversion efficiency,voltage losses,charge separation,organic photovoltaics
更新于2025-11-14 15:18:02
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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
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Thermal-Annealing Effects on Energy Level Alignment at Organic Heterojunctions and Corresponding Voltage Losses in All-Polymer Solar Cells
摘要： Matched energy level alignment is a key requirement for efficient organic devices such as organic light-emitting diodes, photovoltaics, and field-effect transistors. The effect of thermal stress/annealing on energy level alignment and related properties of the devices are less discussed compared to the extensively explored effect on morphology and corresponding device performance. Here all polymer solar cells (all-PSCs) are employed to study thermal annealing effects on energy level alignment and the corresponding effect on the device properties of the all-PSCs. It is found that optimized energy level alignment can be achieved by thermal annealing. An interface dipole layer at the donor/acceptor interface is introduced by energy level realignment that assists charge generation by reducing geminate recombination so that the voltage loss is dramatically reduced, improving the performance of the all-PSCs.
关键词： Thermal Annealing,Voltage losses,Polymer solar cell,General design rule,Energy level alignment
更新于2025-09-19 17:13:59
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Fundamental Aspects Concerning the Validity of the Standard Equivalent Circuit for Large‐Area Silicon Solar Cells
摘要： The standard equivalent circuit of a solar cell amounts to a lumped description by separate diode and resistor elements. Since its application to a large-area silicon solar cell effectively implies averaging the emitter resistance which, however, is closely coupled to the p–n junction, it is not self-evident that it works more or less well. Using an analytically solvable distributed series resistance model and systematically treating the deviations from the ideal case of zero emitter resistance, the equivalent circuit is found in linear order in the sheet resistivity. In this linear order, the lumped voltage losses are fully compatible with the integrated Joule losses; this compatibility turns out to be a necessary and sufficient condition for modeling the local series resistance of a large-area silicon solar cell. In higher orders of the sheet resistivity, however, the lumped voltage losses are not compatible with the integrated Joule losses, which means that the equivalent circuit cannot describe these higher orders. The equivalent circuit resulting from the linear-order lumped series resistance accounts for the experimentally observed variation of the lumped series resistance along the current–voltage characteristic, which turns out to be fully described by a dependence on the dark diode current only.
关键词： Joule losses,equivalent circuit,solar cell modeling,voltage losses,local series resistance
更新于2025-09-12 10:27:22
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How to Report Record Open‐Circuit Voltages in Lead‐Halide Perovskite Solar Cells
摘要： Open-circuit voltages of lead-halide perovskite solar cells are improving rapidly and are approaching the thermodynamic limit. Since many different perovskite compositions with different bandgap energies are actively being investigated, it is not straightforward to compare the open-circuit voltages between these devices as long as a consistent method of referencing is missing. For the purpose of comparing open-circuit voltages and identifying outstanding values, it is imperative to use a unique, generally accepted way of calculating the thermodynamic limit, which is currently not the case. Here a meta-analysis of methods to determine the bandgap and a radiative limit for open-circuit voltage is presented. The differences between the methods are analyzed and an easily applicable approach based on the solar cell quantum efficiency as a general reference is proposed.
关键词： bandgap,nonradiative voltage losses,Shockley–Queisser model,fill factor losses,photovoltaics,radiative limit,recombination
更新于2025-09-12 10:27:22