The voltage loss incurred by nonradiative charge recombination should be reduced to further improve the power conversion efficiency of organic solar cells (OSCs). This work discusses the nonradiative voltage loss in OSCs with systematically controlled energy offset between optical bandgap and charge transfer (CT) states. It is demonstrated that the nonradiative voltage loss is a function of the energy offset; it drops sharply with decreasing energy offset. By measuring the quantum yields of electroluminescence from OSCs and decay kinetics of CT states, it is found that the radiative decay rate of CT states becomes larger when the energy offset is negligible compared with those in conventional OSCs with sufficient energy offset. This behavior is rationalized by hybridization between CT and local excited states, resulting in a considerable enhancement of the oscillator strength of CT states. Based on a trend observed in this study, the precise mechanism by which the energy offset affects the nonradiative voltage loss is discussed.

中文翻译：

---

能量偏移在有机太阳能电池非辐射电压损失中的作用

应减少非辐射电荷复合引起的电压损失，以进一步提高有机太阳能电池（OSC）的功率转换效率。这项工作讨论了OSC中的非辐射电压损耗，其中在光学带隙和电荷转移（CT）状态之间具有系统控制的能量偏移。证明了非辐射电压损失是能量补偿的函数；随着能量补偿的降低，它急剧下降。通过测量来自OSC的电致发光的量子产率和CT状态的衰减动力学，发现当能量偏移可忽略时，与具有足够能量偏移的常规OSC相比，CT状态的辐射衰减率变得更大。这种行为通过CT和局部激发态之间的混合得以合理化，结果大大增强了CT状态的振荡器强度。基于本研究中观察到的趋势，讨论了能量偏移影响非辐射电压损失的精确机制。