LAUSR

Two‐dimensional (2D) photodetecting materials have shown superior performances over traditional materials (e.g., silicon, perylenes), which demonstrate low responsivity (R) (<1 AW−1), external quantum efficiency (EQE) (<100%), and limited detection bandwidth. Recently, 2D indium selenide (InSe) emerged as high‐performance active material in field‐effect transistors and photodetectors, whose fabrication required expensive and complex techniques. Here, it is shown for the first time how molecular functionalization with a common surfactant molecule (didodecyldimethylammonium bromide) (DDAB) represents a powerful strategy to boost the (opto)electronic performances of InSe yielding major performance enhancements in phototransistors, Schottky junctions, and van der Waals heterostructures via a lithography‐compatible fabrication route. The functionalization can controllably dope and heal vacancies in InSe, resulting in ultrahigh field‐effect mobility (103 cm2 V−1 s−1) and photoresponsivity (106 A W−1), breaking the record of non‐graphene‐contacted 2D photodetectors. The strategy towards the molecular doping of 2D photodetecting materials is efficient, practical, up‐scalable, and operable with ultra‐low power input, ultimately paving the way to next‐generation 2D opto‐electronics.