Bifacial CuInSe2 solar cells achieve record efficiency on transparent substrates
by Riko Seibo
Tokyo, Japan (SPX) Jul 22, 2025
The Division of Energy and Environmental Technology at the Daegu Gyeongbuk Institute of Science and Technology (DGIST) has developed a next-generation thin-film solar cell capable of generating electricity from both sides. Spearheaded by Principal Researchers Daehwan Kim and Shijoon Sung, the team fabricated narrow band gap CuInSe2 solar cells using copper, indium, and selenium on transparent electrode substrates, introducing a bifacial architecture that enhances energy yield.
Bifacial solar cells are designed to harvest sunlight from both the front and back sides, boosting power generation without increasing the installation footprint. However, producing high-performance thin-film devices on transparent electrodes has been challenging due to their limited heat tolerance. Traditional fabrication methods require high temperatures, which degrade transparent materials and compromise cell efficiency.
To overcome this, the DGIST team incorporated silver (Ag) into the CuInSe2 compound, enabling the deposition process at a reduced temperature below 420C. They also optimized the device structure by creating a gallium (Ga) gradient at the base of the absorber layer, which improved charge transport and reduced recombination losses. These innovations significantly enhanced the performance of CuInSe2 bifacial solar cells on heat-sensitive transparent substrates.
The resulting devices achieved a notable 15.3% efficiency from the front and 8.44% from the rear, with a bifacial power generation density of 23.1 mW/cm-ranking among the highest globally for thin-film cells of this type.
“This study offers a new possibility to increase efficiency for thin-film solar cells based on transparent substrates,” stated Kim and Sung. “We will further expand the scope of applications for high-efficiency bifacial solar cell technology based on transparent substrates.”
The study was co-authored by PhD student Ali Amanat and researcher Donghwan Jeon. It appeared as the cover article in the June 17 online edition of Advanced Energy Materials.
Research Report:Highly Efficienct Bifacial Narrow Bandgap Ag-CuInSe2 Solar Cells on ITO
Related Links
Daegu Gyeongbuk Institute of Science and Technology
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