Recently, 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 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 due to their high light absorption, suitable band gaps, and good stability. However, their development has stalled for nearly three decades since achieving 12.2% efficiency in high-temperature-processed devices 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, 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 (S2--GPT) process at 180 °C, effectively reducing shallow- and deep-level defects to reduce non-radiative 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 an 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.
CuInS2 thin-film solar cell fabricated by low-temperature solution-processing strategy delivers new records of efficiency and open-circuit voltage. (Image by ZHANG Chaofan)
