Minimizing Recombination Losses of Wide-Bandgap Perovskite for Highly Efficient Perovskite-Based Tandems

Metal halide perovskite-based tandem solar cells are promising green energy candidates to further improve thin film solar cells' efficiency for lower carbon dioxide emission of the energy conversion system. The wide-bandgap perovskite works as a top cell light harvester and typically consists of a mixed halide composition, which is currently limiting the overall tandem performance due to halide-segregation, bromide-involved defects states, and non-ideal contact materials leading to significant recombination losses [1,2]. As a result, the open circuit voltage (<i>V</i>_OC) deficit is larger for perovskites with bandgaps &gt;1.7eV than it is for medium bandgap ones [3,4]. In addition, upscaling the active area is a prerequisite for industrial application.<br/>Here, we develop new triple halide perovskite compositions with bandgaps of ~1.8 eV for all-perovskite tandem and 1.68 eV for perovskite-Si tandem, by combining additives and surface treatments. With the function of the additive and surface treatment, the recombination losses of ~1.8 eV perovskite bulk and interfaces have been reduced, resulting in a long carrier lifetime is up to 3 µs compared to 0.9 µs of the control sample. As a result, the <i>V</i>_OC of a single-junction ~1.8 eV device reached 1.36 V with antisolvent quenching and &gt;1.34 V with nitrogen quenching. By combining with a mixed tin-lead narrow bandgap perovskite as a bottom cell, a certified efficiency of 27.5% for an all-perovskite tandem solar cell is achieved. In addition, the energetic alignment offset between 1.68 eV perovskite and carrier transport materials has been decreased with the help of additive and surface treatment. The carrier lifetime and recombination losses of perovskite film itself and interfaces are also decreased. Finally, the 1.68 eV bandgap perovskite solar cell realized a <i>V</i>_OC of 1.29 V with 23% efficiency for a 0.09 cm² device and 18.0% efficiency on a small module of 4 cm² with 4 subcells. This progress allows us to fabricate highly efficient perovskite-based tandems and accelerate commercialization.<br/><b>References</b><br/>[1] T. Leijtens, K. A. Bush, <i>et al.</i>, <i>Nat. Energy</i> (2018), <b>3</b>, 828–838.<br/>[2] I. Levine, O. G. Vera, <i>et al.</i>, <i>ACS Energy Lett.</i> (2019), <b>4</b>, 1150–1157.<br/>[3] F. Peña-Camargo, P. Caprioglio, <i>et al.</i>, <i>ACS Energy Lett.</i> (2020), <b>5</b>, 2728–2736.<br/>[4] F. Yang, P. Tockhorn<i>, et al., Adv. Mater.</i> (2024), 36, 2307743.