Ultrafast Electrochemical Synthesis of Defect‐Free In ₂ Se ₃ Flakes for Large‐Area Optoelectronics

Because of its thickness-dependent direct bandgap and exceptional optoelectronic properties, indium(III) selenide (In2 Se3 ) has emerged as an important semiconductor for electronics and optoelectronics. However, the scalable synthesis of defect-free In2 Se3 flakes remains a significant barrier for its practical applications. Here, a facile electrochemical strategy is presented for the ultrafast delamination of bulk layered In2 Se3 crystals in nonaqueous media, resulting in high-yield (83%) production of defect-free In2 Se3 flakes with large lateral size (up to 26 µm). The intercalation of tetrahexylammonium (THA+ ) ions mainly creates stage-3 intercalated compounds in which every three layers of In2 Se3 are occupied by one layer of THA molecules. The subsequent exfoliation leads to a majority of trilayer In2 Se3 nanosheets. As a proof of concept, solution-processed, large-area (400 µm × 20 µm) thin-film photodetectors embedded with the exfoliated In2 Se3 flakes reveal ultrafast response time with a rise and decay of 41 and 39 ms, respectively, and efficient responsivity (1 mA W-1 ). Such performance surpasses most of the state-of-the-art thin-film photodetectors based on transition metal dichalcogenides.