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

摘要

All-perovskite tandem solar cells are promising for breaking through thesingle-junction Shockley–Queisser limit, and that potentially raises interestin configuring efficient Sn-Pb alloyed narrow-bandgap perovskite solar cells(PSCs). However, the Sn-Pb alloyed perovskites are commonly plagued byuncontrollable crystallization dynamics and severe p-doping levels. Herein,an effective additive molecule is designed with heterovalent substitutionand antioxidant functions, whereby an organic metal coordinationcompound of tris(2,4-pentanedionato)gallium (TPGa) is employed toupgrade the quality of perovskite films. Ga~(3+) substitution obviously booststhe formation energy of Sn vacancies and heals the trap states. Meanwhile,the crystal structure evolution process is improved by the anchoring effectof 2,4-pentanedionato. The PSCs incorporating these improvements delivernot only a power conversion efficiency of 21.5 but also outstandingstability, as demonstrated by retaining 80 of the initial efficiency forover 1500 h. In addition, 23.14-efficient all-perovskite tandem solar cellsare further obtained by pairing this PSC with a wide-bandgap (1.74 eV)top cell. This study supports the feasibility of doping trivalent ions intothe Sn-Pb alloyed perovskites to compromise the self-p-doping effect andhighlights the importance of acetylacetone for passivating defects andhindering oxidation.