Ultrafast Electrochemical Synthesis of Defect‐Free In₂Se₃ Flakes for Large‐Area Optoelectronics

Abstract Because of its thickness‐dependent direct bandgap and exceptional optoelectronic properties, indium(III) selenide (In₂Se₃) has emerged as an important semiconductor for electronics and optoelectronics. However, the scalable synthesis of defect‐free In₂Se₃ flakes remains a significant barrier for its practical applications. Here, a facile electrochemical strategy is presented for the ultrafast delamination of bulk layered In₂Se₃ crystals in nonaqueous media, resulting in high‐yield (83%) production of defect‐free In₂Se₃ 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 In₂Se₃ are occupied by one layer of THA molecules. The subsequent exfoliation leads to a majority of trilayer In₂Se₃ nanosheets. As a proof of concept, solution‐processed, large‐area (400 µm × 20 µm) thin‐film photodetectors embedded with the exfoliated In₂Se₃ 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.