Isothiourea-based buried interface modification for high-efficiency and stable perovskite solar cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Oxygen vacancies and undercoordinated Pb2+ in SnO2 electron transport layers cause non-radiative recombination in perovskite solar cells.
• This recombination degrades solar cell efficiency and stability, and promotes ion migration.

Purpose of the Study:

• To address non-radiative recombination and ion migration in perovskite solar cells.
• To improve the performance and stability of perovskite solar cells through interface modification.

Main Methods:

• Interface passivation using two multi-functional isothiourea bridge molecules: CESC (S-carboxyethyl isothiourea hydrochloride) and DASC (S-[2-(dimethylamino) ethyl] isothiourea dihydrochloride).
• Application of these molecules at the buried interface between SnO2 and perovskite layers.

Main Results:

• Dual-functional passivation achieved by filling O2- vacancies and binding uncoordinated Pb2+ ions.
• Increased power conversion efficiencies to 18.75% (DASC) and 19.04% (CESC) from 17.20% (control).
• Enhanced stability, with unpackaged cells retaining 91.2% (CESC) and 89.5% (DASC) efficiency after 1000 hours in high humidity.

Conclusions:

• Isothiourea molecules effectively passivate defects at the SnO2/perovskite interface.
• Interface modification with CESC and DASC significantly improves perovskite solar cell performance and stability.