Control of blend morphology at multi-scale is critical for optimizing the power conversion efficiency(PCE)of plastic solar cells.To better understand the physics of photoactive layer in the organic photovoltaic devices,it is necessary to gain understanding of morphology and the corresponding electronic property.Herein we report the correlation between nanoscale structural,electric properties of bulk heterojunction(BHJ)solar cells and the annealing-induced PCE change.We demonstrate that the PCE of BHJ solar cells are dramatically improved(from1.3%to 4.6%)by thermal annealing,which results from P3HT crystalline stacking and the PCBM aggregation for interpenetrated network.The similar trend for annealinginduced photovoltage and PCE evolution present as an initial increase followed by a decrease with the annealing time and temperature.The surface roughness increase slowly and then abruptly after the same inflection points observed for photovoltage and PCE.The phase images in electric force microscopy indicate the optimized P3HT and PCBM crystallization for interpenetrating network formation considering the spectroscopic results as well.From the correlation between surface photovoltage,blend morphology,and PCE,we propose a model to illustrate the film structure and its evolution under different annealing conditions.This work would benefit the better design and optimization of the morphology and local electric properties of solar cell active layers for improved PCE.
Denghua LiHan YanChao LiYanlian YangZhixiang WeiChen Wang
聚合物太阳能电池(polymer solar cells,PSC)因其柔性、易加工性等特点成为目前新能源领域研究的热点之一.扫描探针显微技术(scanning probe microscopy,SPM)在高分辨形貌表征和电特性表征方面具有独特优势,近年来在PSC研究领域的应用逐渐受到广泛关注.本文综述了近年来利用SPM技术在纳米尺度研究PSC活化层的形貌、相分离、电荷分离、电势分布等的新进展,分别介绍静电力显微技术(electric force microscopy,EFM)、导电原子力显微技术(conductive atomic force microscopy,C-AFM)、开尔文探针力显微技术(Kelvin probe force microscopy,KPFM)等在PSC活化层的结构和局域电学特性表征中的应用,并对电特性扫描探针显微技术(electric SPM,ESPM)在PSC及其他具有光电特性的薄膜、器件等研究领域的应用前景进行了展望.
