Limiting factors and improving solutions of P-I-N type tin-lead perovskite solar cells performance

Abstract

In order to break through the limit of Shockley-Queisser (SQ) radiation and further improve the efficiency of perovskite solar cells, tin-lead perovskite solar cells have widely and successfully been used as narrow-bandgap bottom cells in all-perovskite tandem solar cells. The highest efficiency of tin-lead perovskite solar cells has recently reached 21.7%, which, however, is still lower than that of lead-based perovskite solar cells. This article analyzes the main factors that limit the further improving of their performances, and summarizes the effective solutions proposed by researchers in recent years. The main points are as follows: 1) by adding tin-rich additives, strong reducing agents or compounds containing large organic cations, Sn<sup>2+</sup> oxidation is inhibited and the p-doped degree of tin-lead perovskite and the open-circuit voltage loss are reduced; 2) through regulating the composition, changing the method of preparing the perovskite film, adding functional groups or solvent engineering, the crystallization rate of tin-lead perovskite film is delayed and the crystallization quality of the film is improved; 3) by selecting an appropriate electron transport layer or hole transport layer the influence of energy level mismatch on carrier transport or the instability of carrier transport layer on devices can be avoided. Finally, the future development of Sn-Pb perovskite solar cells is prospected. It is believed that the tin-lead perovskite solar cells can realize not only the high efficiency and stable single-junction solar cells, but also high efficiency perovskite-perovskite tandem solar cells.