Researchers from Spain's UPV/EHU, ICIQ-BIST, CIDETEC and Mexico's Instituto Politécnico Nacional have explored the effect of chalcogen substitutions in fullerene derivatives to enhance efficiency and stability of perovskite solar cells.
The team examined the effects of chalcogen substitution in the chemical structure of phenyl-butyric acid methyl ester (PCBM) on the performance and stability of inverted perovskite solar cells (PSCs). PCBMs are the most widely used electron transport materials in inverted PSCs. However, these compounds can suffer from lack of stability under irradiation. In the race for optimizing the PCBM-like derivatives, the thiophene moiety has garnered significant attention for enhancing the performance and stability of PSCs. The novelty in this study relies on the tests done on the selenophene derivative. This compound was compared to thiophene and furan substituted derivatives, and to the reference PCBM without a chalcogenophene moiety, demonstrating a better surface passivation and reduced interfacial charge recombination.
"Our research reveals that the incorporation of selenophene into the fullerene structure significantly improves the performance and stability of perovskite solar cells. By carefully tuning the electron transport layer, we were able to reduce recombination losses and enhance charge mobility, which are crucial for advancing the efficiency of these next-generation solar cells", said Prof. Emilio Palomares, group leader and ICIQ Director.
Additionally, this study investigated the differences between using the fullerene cages C70 and C60 in the PCBM chemical structure. The photovoltaic results demonstrated that the key is the adequate control of the thickness of the electron transport layer. Overall, the improvements result from the reduction in trap-assisted recombination, an increase in electron mobility, and improved charge extraction processes.
"This work investigates the impact of a chalcogen atom substitution on PCBM derivatives that are used as the electron transport layer (ETL) in solar cells. POLYMAT prepared three PCBM derivatives with different chalcogen moieties, whereas the complete fabrication and advanced optoelectronic characterisation of the solar cells were conducted by the Palomares group. Through the analysis of the results, we were able to determine the molecular interactions at the ETL/perovskite interface", according to Dr. José G. Sánchez, one of the lead authors of this work.
