Interfacial electrostatic interaction-enhanced photomultiplication for ultra-high external quantum efficiency of organic photodiodes

Abstract

A photomultiplication-type organic photodiode (PM-OPD), where an electric double layer (EDL) is strategically embedded, is demonstrated with an exceptionally high external quantum efficiency (EQE) of 2,210,000%, responsivity of 11,200 A W− 1, specific detectivity of 2.82 × 1014 Jones, and gain-bandwidth product of 1.92 × 107 Hz as well as high reproducibility. A metal-semiconductor Schottky interface consisting of an EDL enables the stabilization of trapped electron states within the acceptor domains of the photoactive layer by electrostatic interactions, boosting the PM-OPD gain generation. The effects of the EDL on the energetics of trapped electron states are confirmed by numerical simulations based on the drift-diffusion approximation of charge carriers. The feasibility of the fabricated high-EQE PM-OPD is demonstrated via a pixelated prototype image sensor. We believe that this new OPD platform opens up the possibility for the ultra-high-sensitivity organic image sensors, while maintaining the advantageous properties of organics.