Recently, lead-based halide perovskites have gained extensive attention due to their outstanding optoelectronic properties. However, the toxicity of lead would seriously limit its future application. To address these issues, in this work novel ligand-free organic–inorganic hybrid metal halide TBASnCl3 (C16H36NSnCl3) quantum dots are synthesized by a one-pot method at room temperature, and they showed high anti-water stability and high potential applications for high-performance UVC photodetectors. Our experimental data showed that the responsivity of the lateral photodetectors Au/TBASnCl3/Au, in which the active layer (i.e. TBASnCl3) was synthesized by further introducing SnF2 as a precursor besides SnCl2, reached 7.3 mA W−1 with a specific detectivity of 1.67 × 1011 Jones under 0.36 mW cm−2 254 nm illumination at −5 V, and it showed a long lifetime even in an environment with an air humidity of 60%. Therefore, it laid a solid foundation for further fabricating lead-free metal halide optoelectronic devices.