The Role of Optical and Electrical Design on the Reverse Bias Stability of Perovskite / Silicon Tandem Solar Cells

Reverse bias stability is a crucial feature impacting the reliability of solar modules. A solar cell can dissipate large amount of energy if placed in reverse bias upon events reducing its photo current output. Besides reducing the power output, excessive heating can result in hot-spots which could trigger the module failure. Halide perovskite-based photovoltaics add the intrinsic sensitivity of this class of materials to high temperature and electric fields. In this presentation the reverse bias behavior of 2T silicon perovskite tandem solar cells is discussed. The focus is on the electrical and optical design of the tandem cell to ensure the largest protection of the perovskite top cell from the silicon bottom cell. We will show the impact of shunt resistance and voltage breakdown of the silicon sub cell in tuning the reverse bias polarization of the perovskite top cell down to -40V, a value compatible with a bypass diode every 20 cells in series in a 60 cells containing module, in analogy to the standard c-Si modules. The analysis is linked to relevant production processes and materials choices, in order to provide a panoramic on how to improve the reverse bias stabilty of tandem solar cells. Moreover, the role of current mismatch between the two sub cells on the reverse bias stability will be analysed. It is shown the fundamental role of this parameters in determining the reverse bias stability in case of partial shadowing of a solar cell. Finally, the interplay between energy yield and reverse bias protection will be modeled providing guidelines for the optimal design of a tandem solar cell.