Austin M. Kay*, Drew B. Riley*, Paul Meredith, Ardalan Armin and Oskar J. Sandberg*,
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引用次数: 0
摘要
自由电荷的重组是限制太阳能电池和光电探测器等基于有机半导体的光伏器件性能的一个关键损耗机制。通常使用瞬态电荷萃取(CE)实验来估算载流子密度对重组速率的影响以及相关的速率系数。然而,这些实验往往忽略了瞬态萃取过程中的重组效应。在这项工作中,我们利用瞬态漂移扩散模拟研究了 CE 实验对低移动性器件(如基于有机半导体的光伏器件)的有效性。我们发现,重组会导致不完全 CE,从而产生依赖于载流子密度的重组速率常数和被高估的重组阶数;这种效应取决于电荷载流子迁移率和电阻电容时间常数。为了克服 CE 实验的这一内在局限性,我们提出了一个考虑电荷载流子重组的分析模型,并利用数值模拟对其进行了验证,同时利用该模型修正了在实验确定的双分子重组速率常数中观察到的载流子密度依赖性。
A New Framework for Understanding Recombination-Limited Charge Extraction in Disordered Semiconductors
Recombination of free charges is a key loss mechanism limiting the performance of organic semiconductor-based photovoltaics such as solar cells and photodetectors. The carrier density-dependence of the rate of recombination and the associated rate coefficients are often estimated using transient charge extraction (CE) experiments. These experiments, however, often neglect the effect of recombination during the transient extraction process. In this work, the validity of the CE experiment for low-mobility devices, such as organic semiconductor-based photovoltaics, is investigated using transient drift-diffusion simulations. We find that recombination leads to incomplete CE, resulting in carrier density-dependent recombination rate constants and overestimated recombination orders; an effect that depends on both the charge carrier mobilities and the resistance–capacitance time constant. To overcome this intrinsic limitation of the CE experiment, we present an analytical model that accounts for charge carrier recombination, validate it using numerical simulations, and employ it to correct the carrier density-dependence observed in experimentally determined bimolecular recombination rate constants.
期刊介绍:
The Journal of Physical Chemistry (JPC) Letters is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, chemical physicists, physicists, material scientists, and engineers. An important criterion for acceptance is that the paper reports a significant scientific advance and/or physical insight such that rapid publication is essential. Two issues of JPC Letters are published each month.