HMN 2026: How Low-temperature CuInS? solar cells edge past 12.2% mark after nearly 30 years

The research team of Professor Wang Mingtai at the Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, developed a low-temperature solution-processing strategy for fabricating CuInS₂ thin-film solar cells and achieved a CuInS₂ solar cell with an efficiency of up to 12.28%. Their findings were published in Joule.

Photovoltaic energy is a promising source of renewable and sustainable power, but developing solar cells that are efficient, stable and low-cost remains a major challenge. Chalcogenide materials, such as CuInS₂, are attractive candidates because of their high light absorption, suitable band gaps and good stability. However, their development has stalled for nearly three decades after high-temperature-processed devices achieved 12.2% efficiency in 1996.

In this study, the team developed a low-temperature solution-processing strategy that combines two key technological innovations.

They designed an interdigitation architecture in an indium-rich CuInS₂ absorber layer at temperatures below 300°C (572°F), which overcomes the limitations of conventional bilayer structures caused by short charge diffusion lengths and enhances both photon absorption and charge generation. In addition, they introduced a sulfur anion-induced gradient phase transformation (S^2--GPT) process at 180°C (356°F), effectively reducing shallow- and deep-level defects, reducing nonradiative recombination and creating an internal electric field that improves the transport of photogenerated charges.

With these innovations, the CuInS₂ solar cell reached an efficiency of 12.28%, slightly higher than the previous record of 12.2%, and an open-circuit voltage of 0.83 V, indicating a strong power-generating capability. Impressively, even without encapsulation, the device retained 86.3% of its initial efficiency after 500 days under ambient conditions, showing outstanding long-term stability and demonstrating that low-temperature processing can produce both efficient and durable solar cells.

This work provides a scalable, low-cost and stable CuInS₂-based solar cell platform, offering a promising alternative to perovskite solar cells, which still face stability challenges.

Provided by
Hefei Institutes of Physical Science, Chinese Academy of Sciences

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