Conductive-bridge interlayer contacts for two-dimensional optoelectronic devices

Photodiodes based on two-dimensional semiconductors are of potential use in the development of optoelectronic devices, but their photovoltaic efficiency is limited by strong Fermi level pinning at metal–semiconductor contacts. Typical metal–interlayer–semiconductor contacts can address this issue, but can also lead to an increase in series resistance. Here we report a conductive-bridge interlayer contact that offers both Fermi level depinning and low resistance. We create an oxide interlayer that decouples the metal and semiconductor, while embedded gold nanoclusters in the interlayer act as conductive paths that facilitate efficient charge transport. Using these contacts, we fabricate a tungsten disulfide (WS₂) photodiode with a photoresponsivity of 0.29 A W⁻¹, linear dynamic range of 122 dB and power conversion efficiency of 9.9%. Our approach also provides a platform for probing photocarrier dynamics, and we find that contact recombination substantially affects photovoltaic performance. In addition, we illustrate the potential of using photodiodes with these conductive-bridge interlayer contacts as full-colour two- and three-dimensional imagers.