Light ideality factor, the slope of open-circuit voltage versus the logarithm of the illumination intensity, is a topic of continuing debate in solar cells. However, the generally accepted interpretation of the ideality factor will fail when the factor is larger than 2. This work demonstrates that the mechanism for light ideality factor is degeneracy of carriers by using the generalized Einstein coefficient in the drift-diffusion model. Moreover, this work proposes that the light ideality factor should satisfy the relation of 0:1:2:4 under different illumination conditions. This work challenges the generally accepted interpretation of the ideality factor and provides a better understanding of organic solar cells.

光理想系数，开路电压的斜率与照明强度的对数，是太阳能电池中不断争论的话题。但是，当理想因数大于2时，理想因数的一般解释将失败。这项工作表明，通过在漂移扩散模型中使用广义爱因斯坦系数，光理想因数的机理是载波的简并性。此外，这项工作提出，在不同的照明条件下，光理想因子应满足0：1：2：4的关系。这项工作对理想因素的公认解释提出了挑战，并为有机太阳能电池提供了更好的理解。