Effects of Self-Hybridized Exciton-Polaritons on WS2 Photovoltaics

Excitonic semiconductors such as transition metal dichalcogenides (TMDCs) are attractive for next-generation photovoltaics (PVs) with low cost, light weight, and low material consumption. In WS2 and other TMDCs, the simultaneous large optical constants and strong exciton resonance can result in the primary photogenerated species being self-hybridized exciton-polaritons emerging from the strong coupling of excitons and optical cavity modes formed by the WS2. We show that strong coupling can benefit photovoltaic performance, with external quantum efficiencies and power conversion efficiencies enhanced by an order of magnitude, approaching values of 55 and 2%, respectively. Thickness dependent device characterization is performed to study the polariton dispersion, revealing anomalous internal quantum efficiency and fill factor behavior that are attributed to polariton-modified exciton transport processes. Our results uncover a significant mechanism in the photoconversion process for PVs from high index, excitonic semiconductors and indicate the utility of strong coupling for optoelectronic devices.