Lead-free and amorphous organic–inorganic hybrid materials for photovoltaic applications: mesoscopic CH3NH3MnI3/TiO2 heterojunction

Abstract

As one type of organic–inorganic hybrid material, APbX₃ organic–inorganic lead perovskite materials have attracted considerable attention in optoelectronic applications. Although organic–inorganic lead perovskites possess high solar-to-electrical conversion efficiency, the toxic Pb in organic–inorganic lead perovskites is expected to cause environmental pollution in future mass applications. Thus, exploiting Pb-free organic–inorganic hybrid materials is urgently needed. In this study, a lead-free and amorphous CH₃NH₃MnI₃ (a-MAMnI₃) thin film was prepared by spin coating a mixed MnI₂ and MAI precursor solution on an electronic transport layer (ETL)-TiO₂. A mesoscopic a-MAMnI₃/TiO₂ heterojunction was formed by filling the mesoporous TiO₂ layer with MAMnI₃. The architecture of the optoelectronic device is FTO/ETL-TiO₂/a-MAMnI₃/Spiro-MeOTAD/Ag. The photovoltage of the optoelectronic device based on the mesoscopic a-MAMnI₃/TiO₂ heterojunction reached 300 mV under AM1.5, 100 mW cm⁻² simulated illumination. The evident photoresponse was observed at 530 nm green light. The test with 2000 s on/off cycling indicated the good stability and repeatability of the device. The findings pave a way for realizing Pb-free and amorphous organic–inorganic hybrid materials applied to optoelectronic logic devices, photodetectors, and optical memory devices.