Optimizing bifacial all-perovskite tandem solar cell: How to balance light absorption and recombination

The perovskite solar cell has attracted considerable interest for tandem device applications due to its bandgap tunability and high efficiency. Although improvements are made to all perovskite tandem cells, their power output is still not close to that of other tandem devices. One possible way to improve the power output is to absorb the rear incident light as a bifacial device. Unlike all previous work, where the focus for optimizing the design of a bifacial tandem device is light absorption, this paper also considers the recombination losses. The six most influential geometric parameters to the tandem device power output were identified through sensitivity analysis. With a physics-based machine learning methodology, we significantly cut down the computational cost to predict the optimal design for a bifacial four-terminal all-perovskite tandem solar cell under nine different albedo conditions. Furthermore, we quantify the change in the recombination losses for the bottom sub-cell under two scenarios: (1) at optimized configuration; (2) at different albedo. It is found that the optimal hole transport layer thickness for the bottom sub-cell increases at higher albedo and the opposite is true for the perovskite layer. A feasible pathway, balancing light absorption and recombination, is presented to improve the tandem device's power output.