Researchers at China's Wuhan University assume that the practical use of all-perovskite tandem solar cells is hampered by the subpar performance and stability issues associated with mixed tin–lead (Sn–Pb) narrow-bandgap perovskite subcells. In their recent study, they focus on these narrow-bandgap subcells and develop an all-in-one doping strategy for them.
The scientists introduce aspartate hydrochloride (AspCl) into both the bottom poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate) and bulk perovskite layers, followed by another AspCl posttreatment. They show that a single AspCl additive can effectively passivate defects, reduce Sn4+ impurities and shift the Fermi energy level.
Additionally, the strong molecular bonding of AspCl–Sn/Pb iodide and AspCl–AspCl can strengthen the structure and thereby improve the stability of Sn–Pb perovskites.
Ultimately, the implementation of AspCl doping in Sn–Pb perovskite solar cells reportedly yielded power conversion efficiencies of 22.46% for single-junction cells and 27.84% (27.62% stabilized and 27.34% certified) for tandems with 95% retention after being stored in an N2-filled glovebox for 2,000 h.
These results could suggest that all-in-one AspCl doping is a favorable strategy for enhancing the efficiency and stability of single-junction Sn–Pb perovskite solar cells and their tandems.