标题：Unraveling the unstable amorphous phase evolution effect on burn-in loss in polymer-fullerene solar cells
作者：Yang, Xiao-Yu; Niu, Meng-Si; Qin, Chaochao; Bi, Peng-Qing; Chen, Zhi-Hao; Feng, Lin; Liu, Jian-Qiang; Hao, Xiao-Tao
作者机构：[Yang, Xiao-Yu; Niu, Meng-Si; Bi, Peng-Qing; Chen, Zhi-Hao; Feng, Lin; Liu, Jian-Qiang; Hao, Xiao-Tao] Shandong Univ, Sch Phys, State Key Lab Crystal 更多
通讯作者：Hao, XiaoTao;Liu, JQ;Hao, XT
通讯作者地址：[Liu, JQ; Hao, XT]Shandong Univ, Sch Phys, State Key Lab Crystal Mat, Jinan 250100, Shandong, Peoples R China.
关键词：Stability; Burn-in loss; Morphology; Charge transport
摘要：The performance degradation of organic photovoltaics is one of the main limitations to their commercialization, especially an initial, rapid degradation-period, termed as a burn-in loss. Herein, we demonstrate that burn-in loss is caused by the presence of thermodynamically unstable mixed-amorphous phase in the active layer. By using a combination of grazing incidence small angle X-ray scattering and photophysical process experiments, we observe that [6,6]-Phenyl C61 butyric acid methyl ester (PC61BM) molecules rapidly move from the finely-mixed amorphous regimes into crystalline or ordered regimes under accelerated conditions (ISOS-D-2 protocol), resulting in a fast short circuit current (Jsc) burn-in loss. Following an ultraviolet radiation (UV) light processing to control amorphous phase, the kinetics of thermally induced PC61BM crystallization can be slowed down due to the formation of the photo-induced PC61BM dimers in the active layer leading to a smaller burn-in loss. In the case of UV irradiated films, even if the molecules migrated out of amorphous phase, the PC61BM-rich phase becomes loose, rather than the compact and sphere-shaped aggregation, which has been observed in pristine films. These analyses reveal the evolution of thermodynamically unstable amorphous phases eventually leading to a decline power conversion efficiency within a short period of time. The results provide a further design basis of organic photovoltaic materials with good thermal stability and high efficient simultaneously.