Photoinduced degradation of organic solar cells with different microstructures

An in situ measurement setup is established to investigate the photoinduced degradation effects in a controllable inert gas ambient environment for the two different microstructures of poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl-C61-butyricacid methyl ester(PCBM) bulk-heterojunction organic solar cells. The two devices are fabricated with the solvent vapor drying process followed by a thermal annealing(vapor drying device) and only a normal thermal annealing process(control device), respectively. Their power conversion efficiencies(PCEs) and aging features are compared. Their different degradation behaviors in light absorption are confirmed. In addition, irradiation-induced changes in both nanostructure and surface morphology of the P3HT:PCBM blend films treated with two different fabrication processes are observed through scanning electron microscopy and atomic force microscopy. Aggregated bulbs are observed at the surfaces for control devices after light irradiation for 50 h, while the vapor drying devices exhibit smooth film surfaces, and the corresponding device features are not easy to degrade under the aging measurement. Thus the devices having solvent vapor drying and thermal annealing show better device stabilities than those having only the thermal annealing process.     

基于P3HT∶PCBM体异质结有机太阳电池的光老化

使用聚-3已基噻吩(P3HT)和富勒烯衍生物(PCBM)作为给体和受体材料,并制备结构为ITO/PEDOT∶PSS/P3HT∶PCBM/Ca/Al有机太阳电池。采用自主搭建的光老化实验平台,一方面对有机太阳电池在空气氛围下的光老化性能进行深入地研究;另一方面忽略水和氧的影响,研究了在惰性气体的氛围下50 h的光老化实验。研究发现,相对于在惰性气体中光老化样品的开路电压没有变化,在空气中光老化样品的开路电压由0.63 V降低至0.58 V,这说明空气中水和氧对有机太阳电池性能有较大地影响;而在惰性气体下对有机太阳电池的实验表明,光老化后有机太阳电池的短路电流和能量转换效率显著降低,光电转换效率(IPCE)测试表明光老化后活性层光吸收能力也有明显地降低。扫描电子显微镜(SEM)和原子力显微镜(AFM)形貌研究揭示了其性能下降的主要原因,即光老化前后薄膜表面变化明显,方均根粗糙度明显变大是导致器件性能变差的主要原因。