Initial photochemical stability in perovskite solar cells based on the Cu electrode and the appropriate charge transport layers

Abstract This paper presents a study on the initial light-induced degradation in inverted CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite solar cells (PSCs) with a structure of indium tin oxide (ITO)/poly (bis(4-phenyl) (2,4,6-trimethylphenyl) amine) (PTAA)/MAPbI 3 / [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/4,7-diphenyl-1, 10-phenanthroline (Bphen)/Cu under anoxic conditions. The pristine champion devices fabricated by our optimized techniques can achieve a power conversion efficiency (PCE) of ∼18% with a negligible hysteresis. Accelerated by exposure to concentrated sunlight of 200 mW/cm 2 , the short-term degradation tests show that the degradation effects of light exposure on the lattice and electronic structures of the MAPbI 3 active layer are almost negligible and the photoelectric parameters of devices demonstrate superior photochemical stability against illumination, which can be ascribed to the introductions of the Cu electrode and the proper charge transport layers of PTAA and Bphen. As the MAPbI 3 layers are integrated in devices and wrapped in these coverlayers, the volatile decomposition products originated from the photochemical reactions in MAPbI 3 active layer should be restrained inside of the active layer and finally regenerated MAPbI 3 . Moreover, the Cu electrode strongly retards the photochemical reactions by restraining the diffusion of I − ions and further enhances photochemical stability of the devices.