Bioinspired stability enhancement in deuterium-substituted organic-inorganic hybrid perovskite solar cells

In hybrid perovskite solar cells (PSCs), the reaction of hydrogens (H) located in the amino group of the organic A-site cations with their neighboring halides plays a central role in degradation. Inspired by the retarded biological activities of cells in heavy water, we replaced the light H atom with its abundant, twice-as-heavy, nonradioactive isotope, deuterium (D) to hamper the motion of H. This D substitution retarded the formation kinetics of the detrimental H halides in Pb-based PSCs, as well as the H bond-mediated oxidation of Sn2+ in Sn-Pb-based narrow-bandgap PSCs, evidenced by accelerated stability studies. A computational study indicated that the zero point energy of D-based formamidinium (FA) is lower than that of pristine FA. In addition, the smaller increase in entropy in D-based FA than in pristine FA accounts for the increased formation free energy of the Sn2+ vacancies, which leads to the retarded oxidation kinetics of Sn2+. In this study, we show that substituting active H with D in organic cations is an effective way to enhance the stability of PSCs without sacrificing photovoltaic (PV) performance. This approach is also adaptable to other stabilizing methods.

Automated summary

The reaction between hydrogens in organic cations and neighboring halides plays a central role in the degradation of hybrid perovskite solar cells (PSCs). By replacing light hydrogen with heavy non-radioactive deuterium, the motion of hydrogen is hampered, resulting in the retardation of detrimental reactions and improved stability of PSCs. This study demonstrates that substituting active hydrogen with deuterium in organic cations is an effective approach to enhance the stability of PSCs without compromising their photovoltaic performance.