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

Yan, Wenjian; Li, Chongwen; Peng, Cheng; Tan, Shuchen; Zhang, Jiakang; Jiang, Haokun; Xin, Feifei; Yue, Fang et al. · Adv Mater · 2024

basic_science · Level V

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Abstract

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