Effects of Self-Hybridized Exciton-Polaritons on TMDC Photovoltaics

Hybrid light-matter states called exciton-polaritons have been explored to improve excitonic photovoltaic (PV) and photodiode efficiency, but the use of closed cavity structures results in efficiency gains over a narrow band, with losses in the short circuit current density under solar illumination. In WX₂ (X = S, Se), the simultaneous large optical constants and strong exciton resonance can result in self-hybridized exciton-polaritons (SHEPs) emerging from the strong coupling of excitons and optical cavity modes formed by WX₂. We perform thickness dependent device characterization of WS₂ and WSe₂ PVs to show that self-hybridized strong coupling enhances device efficiency on resonance while still enabling broadband absorption, resulting in improved short circuit current density under solar illumination. Ultimately, we leverage strong coupling to achieve external quantum efficiencies as high as 70% and record power conversion efficiencies approaching 7%. This result indicates the utility of SHEPs for light-energy harvesting applications.