Hot-carrier Cooling Regulation for Mixed Sn-Pb Perovskite Solar Cells.

The rapid relaxation of hot carriers leads to energy loss in the form of heat and consequently restricts the theoretical efficiency limit of single-junction solar cells. However, this issue has not received much attention in tin-lead perovskites solar cells. Herein, we introduce tin(II) oxalate (SnC 2 O 4 ) into tin-lead perovskite precursor solution to regulate hot-carrier cooling dynamics. The addition of SnC 2 O 4 increases the length of carrier diffusion, extends the lifetime of carriers, and simultaneously slows down the cooling rate of carriers. Furthermore, SnC 2 O 4 can bond with uncoordinated Sn 2+ and Pb 2+ ions to regulate the crystallization of perovskite and enable large grains. The strongly reducing properties of the C 2 O 4 2- can inhibit the oxidation of Sn 2+ to Sn 4+ and minimize the formation of Sn vacancies in the resulting perovskite films. Additionally, as a substitute for tin(II) fluoride, the introduction of SnC 2 O 4 avoids the carrier transport issues caused by the aggregation of F - ions at the interface. As a result, the SnC 2 O 4 -treated Sn-Pb cells show a champion efficiency of 23.36%, as well as 27.56% for the all-perovskite tandem solar cells. Moreover, the SnC 2 O 4 -treated devices showed excellent long-term stability. This finding is expected to pave the way toward stable and highly efficient all-perovskite tandem solar cells. This article is protected by copyright. All rights reserved.