基于光学与光—电转换模型对聚合物电池功能层厚度与性能相关性分析

本文基于Forouhi-Bloomer 模型得到了这种功能层的光学常数.根据菲涅耳系数矩阵法计算了这种器件内的光电场分布,并计算了不同厚度的聚合物功能层的光子吸收数.同时,通过Onsager-Braun理论,分析了在无外加电场下聚合物功能层厚度对激子分离概率的影响.理论分析和实验结果证明:在特定的薄膜制备工艺下,器件结构为ITO/PEDOT/ P3HT:PC₆₀BM /LiF/Al时,聚合物功能层厚度在100 nm左右时,可以使器件的光子吸收数最大化,同时避免了激子分离概率的降低. 关键词： 光学常数 激子 聚合物太阳能电池

Analysis of the effect of active layer thickness on polymer solar cell performance based on optical and opto-electronic model

Polymer solar cell with excellent performance is currently composed of the blend bulk-heterojunction formed by conjugated polymer as donor material and fullerene as acceptor material, among which P3HT and PCBM are most widely used. For the photoelectric thin film device, the optical and the electric characteristics of the active layer can affect the device performance directly. The optical constants of the active layer are obtained primarily based on the Forouhi-Bloomer model. According to the Fresnel coefficient matrix, the numbers of photons absorbed by different active layer thick devices are investigated by calculating electromagnetic field distributions inside this structure. To make a specific analysis of the thickness effect on dissociation probability of bound pairs without external excitation, the model of Onsager-Braun is adopted. Theoretical analysis shows that the active layer with a thickness of 100 nm can maximize photon absorption by the device without reducing the dissociation probability of excitons obviously. As a result, an optimal thickness of the active layer is about 100 nm, which is confirmed by the theoretical and the experimental results from the device with the structure of ITO/PEDOT/ P3HT:PC₆₀BM /LiF/Al.