Enabling High-Temperature Operation in All-Inorganic, All-Evaporated CsPbI2Br Photodetectors with Transparent Contacts

Abstract

All-inorganic CsPbI2Br perovskites are emerging as leading candidates for high-performance visible photodetectors due to their strong absorption, thermal resilience, and compatibility with complementary metal-oxide semiconductor (CMOS) platforms. However, ion migration under bias or thermal stress leads to trap-assisted leakage and interfacial barrier modulation at transparent conducting oxide (TCO) contacts, compromising device stability at elevated temperatures. In this work, we unravel how indium tin oxide (ITO) and indium zinc oxide (IZO) electrodes govern charge transport, trap–ion interactions, and operational stability in fully evaporated CsPbI2Br photodiodes on glass and Si/TiN substrates. On glass, IZO devices exhibit elevated dark currents, transient photocurrent overshoot, and strong field-induced barrier lowering due to oxygen-vacancy-mediated halide ion accumulation at the TiO2/IZO interface. ITO, in contrast, suppresses ionic polarization, enabling higher external quantum efficiency (EQE), responsivity, detectivity, and linear dynamic range (LDR). Low-temperature J–V analysis confirms that below 240 K, ion migration is frozen and both devices shift to trap-assisted tunneling-dominated transport, underscoring that interfacial differences emerge mainly through ionic activity at higher temperatures. Thermal admittance spectroscopy (TAS) reveals electrode-independent deep traps; however, TCO-dependent trap–ion coupling strength explains the divergent leakage behavior. Remarkably, when integrated on conductive Si/TiN substrates, both IZO and ITO devices exhibit suppressed ionic effects, low leakage, rapid response, and stable performance, emphasizing the critical role of substrate engineering. This study establishes electrode and substrate design as decisive strategies for enabling thermally resilient, ion-stable, CMOS-ready perovskite photodetectors.