The lifetime of photogenerated charge carriers is one of the most important parameters in solar cells, as it rules the recombination rate that defines the open circuit voltage and the required minimum extraction time. It is therefore also one of the most discussed factors in all photovoltaic research fields. Lifetime evaluation of solar cells is frequently conducted via both optical and electrical means with the purpose of obtaining a deeper understanding of the dominant performance limiting recombination mechanisms. In many earlier recombination designations, performed via transient electrical means in novel thin film solar cells, the lifetime has been observed to be a decaying exponential function of the open circuit voltage. In this work we re-evaluate these previously assigned lifetimes as often being severely influenced by capacitive decay rates of spatially separated charge carriers. These “lifetimes” have thus very little in common with lifetimes relevant under steady state operational conditions of the solar cell. We show that the problem of lifetime determination via electrical means arises from that the relaxation of such charges, being associated with quasi-static capacitances of geometric type or from space-charge regions in the device, is also a decaying exponential function of the instantaneous open circuit voltage. This misconception hence also explains the often observed large discrepancy between optically and electrically determined lifetimes. We finally provide a simple expression outlining under what conditions relevant bulk recombination lifetimes are electrically accessible in thin film solar cells.

中文翻译：

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回顾薄膜太阳能电池瞬态电特性的寿命；评估了硅，有机和钙钛矿设备的电容问题†

光生电荷载流子的寿命是太阳能电池中最重要的参数之一，因为它决定了定义开路电压和所需的最小提取时间的复合率。因此，它也是所有光伏研究领域中讨论最多的因素之一。太阳能电池的使用寿命评估通常通过光学和电气手段进行，目的是获得对主要性能限制重组机制的更深入的了解。在许多较早的重组名称中，通过在新颖的薄膜太阳能电池中的瞬态电学手段中，已经观察到寿命是开路电压的衰减指数函数。在这项工作中，我们重新评估了这些先前分配的寿命，这些寿命通常受到空间分离的电荷载流子的电容衰减率的严重影响。因此，这些“寿命”与在太阳能电池的稳态操作条件下相关的寿命几乎没有共同之处。我们证明了通过确定寿命的问题产生电气装置的原因是，与几何类型的准静态电容或设备中的空间电荷区域相关联的此类电荷的松弛也是瞬时开路电压的衰减指数函数。因此，这种误解还解释了通常观察到的光学寿命和电气寿命之间的巨大差异。我们最终提供了一个简单的表达式，概述了在什么条件下薄膜太阳能电池可以电访问相关的本体复合寿命。