Near-UV Phototransistors Based on an All-Inorganic Lead-Free Cs₃Cu₂I₅/CuTCNQ Hierarchical Heterostructure

With the rapid advances in metal halide perovskite optoelectronics, eliminating toxic lead from perovskites has been an urgent demand. However, state-of-the-art lead-free perovskite photodetectors are still challenged with issues of low photoresponse, poor stability, etc. Here, all-inorganic lead-free perovskite (Cs3Cu2I5) single crystals that possess good stability under air exposure are synthesized via a facile solid reaction method. Meanwhile, a higher photoluminescence quantum yield of 95.2% and a prolonged carrier lifetime of 1.127 μs are obtained by further optimizing the synthesis. Benefiting from the polyporous surface and hollow structure of Cu-7,7,8,8-tetracyanoquinodimethane (CuTCNQ) microtubes, more Cs3Cu2I5 nanocrystals can adhere on the innershell and outershell of CuTCNQ-15 microtubes. This unique structure contributes to the improved efficiency of utilizing incident light and promotes charge carrier generation and transportation. As a result, the hierarchical CuTCNQ/Cs3Cu2I5 (hollow microtube/nanocrystal) heterostructure phototransistor exhibits a high responsivity of 88.36 A W–1 and a large detectivity of 1.66 × 1012 Jones. The proposed lead-free perovskites and mixed-dimensional heterojunctions are promising for sensitive light detection.