Conjugated N-Type Diradical Semiconductor Empowers High-Performance TiO₂-Based Perovskite Solar Cells

Titanium dioxide (TiO₂) plays a critical role as an electron transport layer in perovskite solar cells (PSCs). However, the efficiency of TiO₂-based PSCs lags significantly behind that of tin dioxide (SnO₂)-based counterparts, primarily due to their high density of surface defects and low conductivity. In this work, we developed a novel n-type conjugated diradical semiconductor, namely IDT-R, which features suitable energy levels and superior electron mobility. Importantly, when deposited on TiO₂, IDT-R serves a dual function: it effectively passivates surface defects while concurrently enhancing the intrinsic conductivity of TiO₂. This synergistic effect significantly improves electron extraction and transport at the buried interface. Consequently, the devices based on IDT-R deliver a high power conversion efficiency (PCE) of 25.38% along with enhanced thermal stability. This work focuses on modulating the electrical properties of TiO₂ and explores, for the first time, a n-type diradical semiconductor toward interface engineering at the electron-selective contact in PSCs.