To date, a few works have been reported for the photodetectors based on mono‐/multilayer MoSe2 nanosheets.43, 44, 45 Although they show outstanding device characteristics such as remarkable light response, their response speed (15 ms–8 s) remains too low to meet the requirements for practical applications, and broadband light detection is yet to be demonstrated.43, 44, 45 In conventional photodetectors, diode structure with vertical p–n junctions are normally adopted. Therefore response speed could be greatly enhanced due to the presence of strong built‐in electric field at junction interface as well as the shorter carrier transit time.46, 47, 48 In light of this, fabrication of MoSe2 homo‐/heterojunction‐based photodetectors is much desirable to further boost their performance. For instance, Duan et al. demonstrated the lateral epitaxial growth of MoSe2/MoS2 heterojunctions, which showed pronounced photoresponse characteristics.49 Choi et al. also reported the construction of MoSe2/graphene van der Waals heterostructures, and investigated the rapid transfer of photogenerated charge carriers between MoSe2 and graphene.50