Designing Heterovalent Substitution with Antioxidant Attribute for High‐Performance Sn‐Pb Alloyed Perovskite Solar Cells

Abstract All‐perovskite tandem solar cells are promising for breaking through the single‐junction Shockley–Queisser limit, and that potentially raises interest in configuring efficient Sn‐Pb alloyed narrow‐bandgap perovskite solar cells (PSCs). However, the Sn‐Pb alloyed perovskites are commonly plagued by uncontrollable crystallization dynamics and severe p‐doping levels. Herein, an effective additive molecule is designed with heterovalent substitution and antioxidant functions, whereby an organic metal coordination compound of tris(2,4‐pentanedionato)gallium (TPGa) is employed to upgrade the quality of perovskite films. Ga³⁺ substitution obviously boosts the formation energy of Sn vacancies and heals the trap states. Meanwhile, the crystal structure evolution process is improved by the anchoring effect of 2,4‐pentanedionato. The PSCs incorporating these improvements deliver not only a power conversion efficiency of 21.5% but also outstanding stability, as demonstrated by retaining 80% of the initial efficiency for over 1500 h. In addition, 23.14%‐efficient all‐perovskite tandem solar cells are further obtained by pairing this PSC with a wide‐bandgap (1.74 eV) top cell. This study supports the feasibility of doping trivalent ions into the Sn‐Pb alloyed perovskites to compromise the self‐p‐doping effect and highlights the importance of acetylacetone for passivating defects and hindering oxidation.