High-performance circular-polarization-sensitive organic photodetectors based on a chiral plasmonic nanocavity

Chiral photodetectors, optoelectronic devices that can detect circularly polarized light (CPL), have attracted much attention as building blocks of next-generation information technology. However, their performance has been severely limited by the tradeoff between the external quantum efficiency (η_E) and the dissymmetry factor of photocurrent, the latter typically being limited by the small dissymmetry factor of absorption (g_A). This work numerically demonstrates that a circular polarization-sensitive organic photodetector (CP-OPD) based on a chiral plasmonic nanocavity can achieve both high η_E and g_A. The design of the chiral nanocavity, featuring a circular dichroic plasmonic mode with a high photonic density of states in the subwavelength thick photoactive layer, is decoupled with that of the photoactive layer, which enables the independent control of the circular dichroic and photon-to-charge conversion properties. By investigating the interaction between CPL and the molecules constituting the photoactive layer, a design principle of the plasmonic CP-OPD is established, resulting in superior performance with η_E = 23.8 % and g_A = 1.6.