(color online) (a) Schematic diagram of Nb-doping for converting n-MoSe₂ to p-MoSe₂. (b) I_ds–V_ds characteristics measured in different gate configurations. The insets: optical image and schematic of the vertical homojunctions based on MoSe₂. (c) J_d–V_ds curves under different laser powers. The inset: short circuit current and open circuit voltage as a function of P_Laser. (d) EQE and D* with respect to the laser power under different V_ds.^[50]