An interfacial degradation mechanism in inverted perovskite solar cells with a sol–gel derived NiOx hole transport layer

Abstract

NiO_x-based inverted perovskite solar cells (PSCs) exhibit desirable stability and efficiency potential. However, their long-term stability remains a significant concern necessitating the investigation of interfacial stability and degradation mechanisms. Hence, the present study offers a pragmatic comprehension of the degradation pathways of the perovskite (CH₃NH₃PbI₃) layer under environmental stressors. For this purpose, the sol–gel-derived NiO_x-based inverted PSCs were exposed to moisture, oxygen, and heat energy at four different stages of device fabrication. Then, the macroscopic visual image, optical absorption, X-ray diffractograms, and device performance decays were analyzed for these layer-by-layer (LBL) structural samples. Consequently, it was found that the rapid degradation of the inverted PSCs with a NiO_x hole transport layer under humidity, air, and thermal stresses was primarily related to silver diffusion into the perovskite layer and the irreversible breakdown of perovskite into its precursors. Furthermore, the performance of the NiO_x layer for versatile perovskite materials was studied via composition engineering (i.e., mixed cation and anion systems). This work may provide practical insight for improving our understanding of device stability, paving the way for commercialization.