Simplified surface defects of Sn-Pb perovskite for efficient all-perovskite tandem solar cells

Abstract

Alloyed Sn-Pb perovskites are demonstrating an increasingly important position due to ideal bandgaps for single and tandem applications. However, Sn incorporation would cause more complex defect management such as boosted deep defect density, serving as highly efficiently non-radiative recombination centers. Traditional one-step passivation methods cannot well passivate these complex defects, making it difficult to further improve open-circuit voltage and efficiency. To fundamentally solve this issue, here we develop a sequential passivation (se-passivation) approach to reconstruct defect types from complexity into simplicity, which then can be efficiently passivated by using well-developed comprehensive passivation strategies. Consequently, vacuum-assisted deposited Sn-Pb perovskite solar cells achieve a record open-circuit voltage of 0.91 V with a nonradiative loss as low as 60 mV. Combining with a 1.79- eV wide-bandgap front sub-cell, we delivered an astonishing efficiency of 28.16 % in all-perovskite tandem solar cells.