Elucidating the underlying physics in a two-terminal all-perovskite tandem solar cell: A guideline towards 30% power conversion efficiency

Abstract

We develop an optoelectronic model for a two-terminal all-perovskite tandem solar cell comprising a top cell, a bottom cell, and a recombination junction in between that connects the two sub-cells in series electrically. In short, the model considers incoherent and coherent light propagation in the glass and thin-film layers respectively, as well as charge carrier transport, generation, and recombination. After calibrating the model to the state of the art two-terminal all-perovskite tandem solar cell with an efficiency of 24.5%, we first study the current matching behavior and S-shaped current–voltage curve of this tandem cell due to the recombination junction. Next, the light interference effect is investigated. Layer thicknesses are adjusted to increase the short circuit current. From a loss analysis, the leading order recombination channels are the surface and Shockley–Read–Hall recombinations. Moreover, we show that the power conversion efficiency of this calibrated tandem model can reach 30.5% by adjusting the layer thicknesses, increasing carrier mobility, and reducing recombination loss. Finally, after switching to bifacial operation, the model predicts a power conversion efficiency of around 35%.