ETRI develops eco-friendly colour CIGS solar cells
Korean team replace CdS buffer layer with zinc- based materials to achieve 18 percent conversion efficiency
Research on solar cells to secure renewable energy sources are ongoing around the world. The Electronics and Telecommunications Research Institute (ETRI) in South Korea succeeded in developing eco-friendly colour Cu(In,Ga)Se2 (CIGS) thin-film solar cells.The research was published in the journals Nano Energy and Progress in Photovoltaics: Research and Application.
CIGS thin-film solar cells are made by coating multiple thin films on a glass substrate. They have a relatively higher absorption coefficient among non-silicon based cells, resulting in high conversion efficiency and long stability. Also, they require less raw materials compared to silicon-based cells; hence less process and material costs.
One downside has been the difficulty in commercialisation as they use a buffer layer which contains toxic heavy metal, cadmium. Thus, the ETRI team replaced the CdS buffer layer with zinc (Zn) based materials - which is not harmful - and managed to achieve approximately 18 percent conversion efficiency; thus eliminating the obstacle to commercialisation.
Likewise, the availability of more than seven colours including purple, green, and blue - without the need for additional process or cost - means one step closer to full-on commercialisation. Moreover, the researchers succeeded in identifying a new analysis method using photo-pumping terahertz spectroscopy and a mechanism for improving the conversion efficiency of solar cells with Zn-based buffer layers.
The solar cells are only 3? thick and can be coated on a flexible substrate as well as a glass substrate. This means that they could be bent or folded, expanding applications as a next-generation eco-friendly energy source.
"This technology will contribute to the solar power system development through the production of high value-added colour photovoltaic modules," said Yong-Duck Chung, the ETRI principal researcher.
'Ultrafast wavelength-dependent carrier dynamics related to metastable defects in Cu(In,Ga)Se2 solar cells with chemically deposited Zn(O,S) buffer layer' by Woo Jung Lee et al; Nano Energy, Volume 74, August 2020.
'Color tuning in Cu(In,Ga)Se2 thin‐film solar cells by controlling optical interference in transparent front layers' by Dae‐Hyung Cho et al; Progress in Photovoltaics: Research and Applications, first published 25th March 2020