Gradient layer arrangement for modulating the buried interface of inverted perovskite solar cells

The surface modification of transparent conductive oxides with self-assembled monolayers (SAM) based on carbazole has been demonstrated to be a workable strategy for the formation of efficient hole-selective contacts, thus significantly enhancing the power conversion efficiency (PCE) and stability of p-i-n perovskite solar cells (PSCs). While the inherent monolayer nature of SAM offers unique advantages, the buried interface poses a significant challenge to synergistic regulation for both perovskite (PVK) and SAM. In this study, an interfacial layer composed of an ionic compound, 3-(methylthio) propylamine hydroiodide (3MTPAI), is introduced between the PVK and SAM layers to enhance the photovoltaic performance of PSCs. 3MTPAI has been demonstrated to enhance the ion–dipole interactions of the SAM, facilitating a better-matched energy level between the PVK and hole transport layer (HTL). This, in turn, improves hole extraction/transport from the PVK layer to the HTL and reduces carrier recombination of the PSCs. Consequently, the PCE of the PSCs modified with 3MTPAI increases from 23.90 % to 25.30 %. Furthermore, devices treated with 3MTPAI exhibit enhanced stability, maintaining 90 % of the original PCE after 1000 h under conditions of 55 ± 5 % RH. Therefore, the buried interface modification strategy employing dual-role 3MTPAI molecules emerges as a viable approach to enhance the efficiency and stability of PSCs.