聚合物:富勒烯薄膜光伏电池的反常高温热稳定性研究

聚合物太阳能电池光电转换效率已接近商业化要求,但稳定性差却成为其实用化瓶颈因素.高温暴晒是聚合物太阳能电池实用化必须面临的环境,因此提高聚合物太阳能电池的热稳定性至关重要.本文以典型的Poly(3-hexylthiophene-2,5-diyl(P3HT):6,6]-Phenyl-C61-butyric acid methyl ester(PC61BM)基聚合物太阳能电池为研究模型,考察其在不同加热温度下(50~110℃)持续工作时的器件效率变化行为,结果发现电池在高温下表现出一种非常规的性能衰减再回升的行为,具体表现为高温下电池首先表现指数式急速衰减(20%~25%),随后发生反常的性能快速恢复至接近初始效率,之后电池保持超长的高温稳定性.光学显微镜和激光光束诱导电流成像结果证明,顶电极覆盖可以有效抑制活性层中PC61BM的聚集结晶,因而电池的反常热诱导稳定性提升与PC61BM的大量聚集结晶无关.活性层薄膜的紫外可见吸收光谱和器件外量子效率的表征结果证明,持续高温加热没有促进PC61BM二聚体的形成,反而有利于PC61BM二聚体的解离.综合实验分析结果,推测PC61BM在光照下的快速二聚反应及其高温解离是导致电池表现出反常热稳定性提升行为的主要原因.实验结果揭示了初期制备的聚合物太阳能电池实际处于一种亚稳态,对器件进行短暂的前期热退火有利于稳定活性层结构,消除亚稳态,有效提升器件稳定性.本研究工作不仅对富勒烯基聚合物太阳能电池的热诱导反常稳定性提升机理机制给出了解释,而且提供了一种提高聚合物太阳能电池稳定性的新策略.

Study on the Abnormal High Temperature Thermal Stability of Polymer:Fullerene Photovoltaic Cells

The power conversion efficiency of polymer solar cells(PSCs)is approaching commercial requirements,but its poor stability has become the next key challenge before the commercialization of PSCs.The high temperature working environment is what PSCs must endure in actual work,so it is necessary to improve the thermal stability of PSCs.Poly(3-hexylthiophene-2,5-diyl(P3HT):6,6]-Phenyl-C61-butyric acid methyl ester(PC61BM)-based PSCs was used as a research model to investigate its degradation behavior at different annealing temperatures(50?110℃).The results show that the PSCs exhibit an abnormal thermally induced stability enhancement behavior.During the high temperature aging process,the power conversion efficiency(PCE)of PSCs abruptly decay 20%?25%within the first 10 h,and then quickly recovered within 200 h,and finally remained stable for a long time(1000 h).Optical microscopy and laser beam induced current imaging characterizations prove that the top electrode covering can effectively inhibit the aggregation and crystallization of PC61BM in the active layer,so the abnormal aging behavior of the PSCs is not caused by the large amount of aggregation of PC61BM.Ultraviolet-visible absorption and external quantum efficiency characterizations prove that continuous high-temperature heating does not promote PC61BM dimerization,but facilitates the dissociation of PC61BM dimers.Based on all the above experimental results,it is speculated that the dimerization of PC61BM and the dissociation of its dimer at high temperature are the main reasons for the abnormal thermal stability enhancement of PSCs.This study also reveal that the newly prepared PSCs are actually in a metastable state,and a short-term thermal annealing of the device in the early stage is helpful to improve the stability of PSCs.This research work not only explains the thermally induced abnormal stability enhancement mechanism of fullerenebased PSCs,but also provides a new strategy to improve the stability of PSCs.