Enhancing efficiency of tin-based perovskite solar cells

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 interest in tin-based perovskite, which offers a more environmentally friendly alternative.

However, a challenge of 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 sandwiches between a hole transport layer and an electron transport layer; in this study, researchers from the University of Tsukuba used 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 utilised in the electron transport layer, the researchers found that the resulting band bending effectively suppresses charge recombination, leading to higher open-circuit voltage.

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

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