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Researchers at University of Tsukuba have elucidated the mechanism that allows for higher open-circuit voltage in environmentally friendly tin-based perovskite solar cells by optimizing the electron transport layer through electron spin resonance. This discovery is significant for advancing the efficiency of tin-based perovskite solar cells.

Tsukuba, Japan—Perovskite solar cells are gaining attention as the next generation of solar technology due to their high efficiency, flexibility, and potential for printing. Although lead-based perovskite has been used in high-efficiency solar cells, concerns regarding lead toxicity have led to increased interest in tin-based perovskite, which offers a more environmentally friendly alternative and a wide range of practical applications.

One challenge facing tin-based perovskite solar cells is their lower energy conversion efficiency compared to their lead-based counterparts. The use of indene-C₆₀ diadduct (ICBA), which consists of two indene molecules bonded to fullerene (C₆₀), is known to enhance performance in the electron transport layer. However, the precise mechanism behind this improvement has yet to be fully understood.

Perovskite solar cells are structured with a perovskite crystal sandwiched between a hole transport layer and an electron transport layer. In this study, researchers employed electron spin resonance to observe electron diffusion at the interface between the tin-based perovskite and the electron transport layer, while also examining band bending at this interface.

The investigation revealed that conventional PCBM, a fullerene derivative used in the electron transport layer, induces band bending at the interface with tin-based perovskite, facilitating charge recombination. This charge recombination leads to a reduction in open-circuit voltage (the maximum voltage available for extraction). By contrast, when ICBA is utilized in the electron transport layer, the researchers found that the resulting band bending effectively suppresses charge recombination, leading to higher open-circuit voltage.

These findings are expected to enhance the efficiency of tin-based perovskite solar cells.

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This work was partially supported by Japan Science and Technology Agency, MIRAI (JPMJMI20C5, JPMJMI22C1, and JPMJMI22E2); Japan Science and Technology Agency, SPRING (JPMJSP2124); New Energy and Industrial Technology Development Organization, Green Innovation; Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research (24K01325); University of Tsukuba, Organization for the Promotion of Strategic Research Initiatives. YS acknowledges partial support from Japan Society for the Promotion of Science, KAKENHI (JP20H00387).

Original Paper

Title of original paper:

Electron diffusion at Sn perovskite/fullerene derivative interfaces and its influence on open-circuit voltage

Journal:

npj Flexible Electronics

DOI:

10.1038/s41528-025-00424-5

Correspondence

Professor MARUMOTO Kazuhiro
Institute of Pure and Applied Sciences, University of Tsukuba

Related Link

Institute of Pure and Applied Sciences