Coexisting and cooperating light-matter interaction regimes in a polaritonic photovoltaic system

Common quantum frameworks of light–matter coupling demonstrate the interaction between an atom and a cavity occurring through a single feedback channel: an exciton relaxes by emitting a photon that is stored in the cavity for several roundtrips before being re-absorbed to create another exciton, and so on. However, the possibility for the excited system to relax through two different channels belonging to two different regimes has been, until now, neglected. Here, we investigate the case in which the strong coupling regime and the photovoltaic effect cooperate to enhance the wavelength-dependent photocurrent conversion efficiency (defined as the incident photons to converted electrons ratio, namely the external quantum efficiency—EQE) of a photovoltaic cell specifically engineered to behave as an optical cavity tuned to the excitonic transition of the embedded active material (CH3NH3PbI3 perovskite). We exploit the angular dispersion of such photovoltaic cell to show that when the cavity mode approaches the energy of the exciton, the strong coupling regime is achieved and the EQE is significantly enhanced with respect to a classic configuration serving as a benchmark. Our findings do not aim at demonstrating an immediate impact in enhancing the performance of photovoltaic systems but, rather, constitute a proof-of-principle experimental demonstration of how the photovoltaic effect can benefit from the generation of polaritons. Nonetheless, such a peculiar cooperating dual-light–matter interaction could be exploited in future polaritonic photovoltaic architectures.