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Highlights2D Mo2C was produced by a modified chemical vapor deposition method, and 2D Mo2C-Au was formed as an asymmetric contact structure with a large work function difference.Mo2C/MoS2/Au photodetectors powered by asymmetric contact structure can work under self-powered condition with a responsivity of 10−1 mA W−1. The detection performance of the photodetectors can be stable for at least 110 days.AbstractSelf-powered devices are widely used in the detection and sensing fields. Asymmetric metal contacts provide an effective way to obtain self-powered devices. Finding two stable metallic electrode materials with large work function differences is the key to obtain highly efficient asymmetric metal contacts structures. However, common metal electrode materials have similar and high work functions, making it difficult to form an asymmetric contacts structure with a large work function difference. Herein, Mo2C crystals with low work function (3.8 eV) was obtained by chemical vapor deposition (CVD) method. The large work function difference between Mo2C and Au allowed us to synthesize an efficient Mo2C/MoS2/Au photodetector with asymmetric metal contact structure, which enables light detection without external electric power. We believe that this novel device provides a new direction for the design of miniature self-powered photodetectors. These results also highlight the great potential of ultrathin Mo2C prepared by CVD in heterojunction device applications.