Performance Potential for Locally Contacted Perovskite Solar Cells

Abstract

In perovskite solar cells (PSCs), a common characteristic of highly effective interface passivation materials is low conductivity. Gains in voltage are thus often disproportionately offset by resistive losses. Local contact approaches can minimize this trade-off and have a proven track record in conventional silicon photovoltaics. Indeed, recent record efficiencies for centimeter-scale PSCs exploit architectures where the passivation layer partially covers the perovskite-transport layer interface. Herein, a three-dimensional numerical device model is used to determine practical performance limits to local contact geometries and consider both the optimum contact dimensions and the trade-offs involved in relaxing these dimensions for ease of fabrication. It is observed that the potential for substantial power conversion efficiency (PCE) increases with local contacts. In devices where power loss occurs solely through recombination at the contacted interface, PCE can be enhanced by up to 10% absolute compared to a full-area contact. However, optimum PCEs depend on contacts on the order of nanometers. It is shown that more fabrication-friendly micrometer-scale contacts still boost PCE, but the absolute enhancement falls short due to the relatively low bulk perovskite charge carrier diffusion length. This may ultimately motivate methods of interface engineering that produce “effective” local contact geometries at nanometer scales, such as via self-forming layers.