Lead halide perovskite sensitized WSe₂ photodiodes with ultrahigh open circuit voltages

Two-dimensional semiconductors (2DSCs) have attracted considerable interests for optoelectronic devices, but are often plagued by the difficulties in tailoring the charge doping type and poor optical absorption due to their atomically thin geometry. Herein, we report a methylammonium lead iodide perovskite (CH₃NH₃PbI₃)/2DSC heterojunction device, in which the electric-field controllable ion migration in the perovskite layer is exploited to induce reversible electron- and hole-doping effects in the underlying monolayer tungsten diselenide (WSe₂) to form a programmable p–n photodiode. At the same time, the CH₃NH₃PbI₃ layer functions as a highly efficient sensitization layer to greatly boost the optical absorption and external quantum efficiency (EQE) of the resulting photodiode. By asymmetrically poling the perovskite layer, gold-contacted CH₃NH₃PbI₃/WSe₂ devices show a switchable open circuit voltage up to 0.78 V, along with a high EQE of 84.3%. The integration of tunable graphene-contacts further improves the photodiode performance to achieve a highest open circuit voltage of 1.08 V and a maximum EQE of 91.3%, greatly exceeding those achieved previously in 2DSC lateral diodes. Our studies establish a non-invasive approach to switch optoelectronic functions and open up a new avenue toward high-performance reconfigurable optoelectronic devices from 2DSCs.