Fig. 1: Operation, device structure, and EQE of a PM-OPD.

Schematic energy diagram a under dark at flat band condition and b negatively biased under illumination. c schematic device structure. d Voltage-dependent EQE (solid lines) of the device shown in c comprising ZnPc blended with C₆₀ at 3 wt%. Each line corresponds to one symbol in d. Dashed red line shows the absorption spectrum of the same blend. Additionally, in e, the relative enhancement factor as a function of applied reverse bias is presented. Symbols show the ratio between EQE at 670 nm at each voltage from d normalized by the EQE at 670 nm at 0 V. The blue line is a guide to the eye. Note that no saturation is observed, indicating that EQE can be further increased. Inset shows the chemical structure of C₆₀, ZnPc and HATNA-Cl₆. The energy level values of ZnPc, C₆₀, and HATNA-Cl₆ in a are taken from the literature^55,56,57.