Maximising photocurrent in ultrathin Nb-doped MoS2 Schottky solar cells

In ultrathin transition-metal dichalcogenide (TMDC) Schottky solar cells, photocurrent is difficult to control when rectifying-junction formation and hole extraction cannot be optimised independently. Here we separate these functions in Nb-doped MoS2 devices and show that the photogenerated current can be predicted to first order from its optical limit. Using dry van der Waals assembly, we contact p-MoS2 through a heavily doped p+-MoS2/Au hole-extraction layer while independently defining the rectifying interface with Cr or Ag. Scanning photocurrent microscopy localizes the response to the metal/p-MoS2 overlap, and EQE combined with transfer-matrix modelling shows that the spectral photocurrent follows absorptance in the MoS2 layer of the full optical stack. In a before-and-after test on the same device, adding h-BN increases the modelled absorbed-photon limit and the measured photovoltaic output, consistent with h-BN modifying MoS2 absorptance through thin-film interference in the multilayer stack. Across Ag-contacted devices, the experimental photogenerated current density scales with the stack-specific optical-limit current density and is described by an effective AM1.5G-weighted collection factor of approximately 0.86. A representative device reaches 3.0% power conversion efficiency under AM1.5G illumination. These results provide a practical way to predict and improve photocurrent in ultrathin TMDC Schottky photovoltaics from measurable stack parameters.