A P-Type Organic Dye as Interface Layer for Efficient and Stable Inverted Perovskite Solar Cells

Nickel oxide (NiO_x) is a promising hole-transport material widely used in inverted perovskite solar cells (PSCs) due to its high carrier mobility and good transparency. However, light-induced degradation of the NiO_x-perovskite heterojunction remains the main factor limiting the long-term operational lifetime of these solar cells. In this study, a traditional p-type organic dye (TPA-CN), commonly used in p-type NiO_x dye-sensitized solar cells, is employed as self-assembled monolayer (SAM) molecules for interface modification between NiO_x and perovskite in inverted PSCs. In TPA-CN, carboxyl anchoring groups passivate Ni^{3 +} defects on NiO_x and enhance hole extraction, while the cyano group passivates undercoordinated Pb^{2 +} in the buried perovskite layer, lowering trap density. Furthermore, TPA-CN functions as an interfacial bridge, boosting charge transfer from the perovskite to NiO_x, which improves both the performance and stability of perovskite solar cells (PSCs). As a result, TPA-CN-modified devices achieve a peak power conversion efficiency (PCE) of 25.54%, compared to 21.80% for unmodified control devices. Notably, unencapsulated devices maintain 89.2% of their initial PCE after 1800 h under ambient conditions (ISOS-D-1) and 95.3% after 500 h of continuous 1-sun illumination. This research presents an effective molecular design approach for developing high-performance inverted PSCs using charge-selective materials.