In a groundbreaking development, researchers have pushed the boundaries of solar cell technology, achieving a significant leap in efficiency for lightweight, flexible solar cells. The study, led by Yukiko Kamikawa from the Global Zero Emission Research Center at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, has resulted in a notable advancement in the field of thin-film solar cells. The research, published in the journal Small Science, focuses on Cu(In,Ga)Se2 (CIGS) solar cells, which are known for their potential in flexible and lightweight applications.
The team at AIST has managed to enhance the performance of CIGS solar cells by addressing key challenges associated with low growth temperatures. By incorporating silver (Ag) alloying, sodium (Na) doping using alkali-silicate-glass thin layers (ASTLs), and cesium fluoride (CsF) post-deposition treatment (CsF-PDT), along with front shallow gallium (Ga) grading, the researchers have significantly improved the efficiency of these solar cells. The result is a conversion efficiency of 21.2%, a low voltage deficit of 0.346 V, and a high short-circuit current density of approximately 40 mA/cm². “The combination of these techniques has allowed us to achieve a high-quality CIGS absorber, which is crucial for improving the overall performance of the solar cells,” Kamikawa explained.
The study highlights the importance of optimizing the CIGS absorber’s quality through alkali doping and Ag alloying. This optimization is essential for benefiting from the surface field (SF) created by front shallow Ga grading. The SF increases the electrical field at the CIGS surface under forward bias voltage, which in turn improves the interfacial properties by repelling holes and reducing carrier recombination. “Device simulations have shown that the SF effectively enhances the electrical field at the CIGS surface, leading to better performance,” Kamikawa noted.
The implications of this research are far-reaching for the energy sector. The development of lightweight, flexible, and highly efficient solar cells opens up new possibilities for integrating solar power into a wide range of applications, from portable electronics to building-integrated photovoltaics. The ability to achieve high efficiency at lower growth temperatures also makes the manufacturing process more cost-effective and environmentally friendly.
This breakthrough could pave the way for future advancements in solar technology, particularly in the development of bottom cells for tandem solar cells. The findings suggest that by improving the bulk quality of the CIGS absorber, researchers can further enhance the performance of solar cells, making them more competitive in the market. As the demand for renewable energy continues to grow, innovations like these will be crucial in driving the transition to a more sustainable future.
