Despite the very different underlying physics of organic photovoltaics (OPVs), inorganic p-n junction’s Shockley’s diode equation is often applied to describe current density–voltage (JV) curves of OPVs. The model parameters, including the diode saturation current, diode ideality factor, series, and parallel resistances, are usually extracted and treated as constants in JV curve analyses. In this work, we develop a drift-diffusion bilayer interface (DD-BI) model for bilayer OPVs, which treats the donor–acceptor (D–A) heterojunction using the detailed balance between densities of polaron pairs, free electrons, and free holes. From the DD-BI model, we derive a diode equation, which is of Shockley’s equation form, but each parameter is explicitly written in terms of the D–A interface properties. We call this model the self-consistent diode (SCD) model as it is consistent with the DD-BI results provided that the key parameters are from the simulation data. By studying the effects of light intensity and carrier mobility, we find that the Shockley SCD parameters are voltage dependent because of space charge accumulation around the D–A heterojunction. Our models are successful in explaining the common discrepancies in OPV JV curve analyses, such as the validity of fitting for series resistance, deviation of ideality factor from the theoretical values, and different resistance values under light and dark conditions. The results provide a better understanding of OPVs with a D–A heterojunction and how we can capture its physics using the SCD equation.

中文翻译：

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双层有机光伏等效电路参数的电压依赖性

尽管有机光伏（OPV）的基本物理原理非常不同，但无机pn结的Shockley二极管方程式通常用于描述OPV的电流密度-电压（JV）曲线。通常会提取模型参数，包括二极管饱和电流，二极管理想因数，串联电阻和并联电阻，并将其视为在JV曲线分析中的常数。在这项工作中，我们开发了用于双层OPV的漂移扩散双层界面（DD-BI）模型，该模型使用极化子对，自由电子和自由空穴的密度之间的详细平衡来处理施主-受主（DA）异质结。 。从DD-BI模型中，我们推导出了二极管方程式，它是Shockley方程式的形式，但是每个参数都是根据D–A界面属性明确编写的。我们将此模型称为自洽二极管（SCD）模型，因为它与DD-BI结果一致，只要关键参数来自仿真数据即可。通过研究光强度和载流子迁移率的影响，我们发现，由于D–A异质结周围的空间电荷积累，Shockley SCD参数与电压有关。我们的模型成功地解释了OPV JV曲线分析中的常见差异，例如，串联电阻拟合的有效性，理想因子与理论值的偏差以及在明暗条件下的不同电阻值。结果提供了对具有D–A异质结的OPV的更好理解，以及我们如何使用SCD方程捕获其物理信息。