Unconventional organic solar cell structure based on hyperbolic metamaterial

Abstract

Hyperbolic metamaterial (HMM) has attracted considerable attention due to its enhanced light-matter interaction for tuning the photonic density of states and producing bulk plasmon polariton (BPP). In this study, we demonstrate the application of HMM in organic solar cells (OSCs) with superior performance for the first time. The designed HMM structure composed of multiple pairs of MoO₃/Au stacks possesses a hyperbolic dispersion behavior in the primary light absorption regime of the photoactive material. To effectively couple BPP into the photoactive layer, the first pair of the HMM structure is designed to be a portion of the OSC structure, serving as the hole transport layer and anode. The unconventional HMM incorporated OSCs (HMM-OSCs) exhibit ∼29.4% enhancement in the power conversion efficiency (PCE) relative to similar OSCs using one pair of MoO₃/Au and ∼11% improvement in PCE as compared to conventional OSCs with the fully reflective electrode. Compared to conventional OSCs, the performance improvement is primarily from the improved short circuit current density from a broad wavelength range of the enhanced photon-to-charge conversion efficiency due to the higher exciton generation and dissociation probability, as suggested by the photocurrent analysis and steady-state photoluminescence measurements. The experimental observation agrees well with that inferred from theoretical simulation for the enhancement in the local electric field and exciton generation rate for the designed HMM structure. Therefore, the designed HMM-OSCs can successfully couple BPP into operation with a large impact on light absorption efficiency enhancement. Our design principle can serve as a useful guideline for the application of HMM in other optoelectronic devices.