Perovskite Silicon Tandem Solar Cells with 39.5% Power Conversion Efficiency: Science or Fiction?

Fully-textured perovskite silicon tandem solar cells merge between a high efficiency potential and compatibility to existing silicon production lines, making them a suitable candidate for wide scale photovoltaic deployment. In this work, we delve in a first step into the dynamics of perovskite crystallization by monitoring the structural evolution from precursor to perovskite phase via in-situ X-ray diffraction, and outline guidelines to obtain highly crystalline perovskite films. Then, we investigate the impact of different process parameters on shaping the final perovskite film properties. Incorporated in a fully-textured tandem architecture, the device delivers 26.7% efficiency. A loss analysis reveals that high series resistance and non-radiative recombination losses at the perovskite/electron transport layer (C60) interface severely limit the performance. We tackle these losses simultaneously by employing a multifunctional perovskite crystallization and surface passivation agent enabling the fabrication of a 30.0% efficient tandem solar cell. Looking one step ahead, experimentally identified solar cell parameters are combined to an opto-electrical simulation model, thus determining a device practical efficiency potential of 39.5% for this tandem solar cell design.