Chiral Molecular Environment Determining Selective Coordination of Cysteine to Perovskite Halogen Vacancies

Amino acid, with amino, carboxyl, and other functional groups in one molecule, is proposed as an effective multisite passivator for perovskite solar cells (PSCs). However, the chirality-induced difference in photovoltaic properties of PSCs caused by subtle changes of the molecular environment between enantiomers of the amino acid has received almost no attention. Herein, for the first time, l- and d-cysteine are introduced into carbon-based fully printable mesoscopic PSCs as additives and 17.41 and 15.12% of power conversion efficiency are obtained, respectively. The essential causes of the differences in photoelectric conversion performances are deeply explored within a density-functional theory (DFT) framework and relative photophysical characterization. DFT reveals that the enhancement of negative surface electrostatic potential around the carboxyl group is due to the chiral molecular environment favoring intramolecular charge transfer with l-cysteine, strengthening the coordination to undercoordinated Pb2+ (halide vacancy) defects. In addition, the advantages of the chiral environment of l-cysteine are also reflected in the inhibition of nonradiative recombination, perovskite crystallization, stability, and light capture, etc. It opens up a novel research pathway extending passivation mechanism from functional groups to the molecular environment.

Automated summary

In this study, L- and D-cysteine were introduced into carbon-based fully printable mesoscopic perovskite solar cells as additives, achieving power conversion efficiencies of 17.41% and 15.12% respectively. Density functional theory (DFT) was used to explore the reasons for the differences in photoelectric conversion performance, including enhanced negative surface electrostatic potential, inhibition of nonradiative recombination, improved perovskite crystallization, stability, and light capture.