Recently, solar cell researchers from Uppsala University in Sweden collaborated with the European Technical Centre of First Solar to publish their findings in the academic journal Nature Energy, achieving a record-breaking efficiency of 23.64% in generating electricity from copper indium gallium selenide (CIGS) solar cells.
According to data from the International Energy Agency, the deployment of solar panels globally is rapidly increasing, with solar power accounting for over 6% of global electricity generation in 2022.
The most important characteristics of solar cells are their ability to absorb light and efficiently transfer energy to electrical loads, thereby minimizing energy loss caused by conversion to heat within the cells.
Currently, the best solar modules can convert sunlight into electricity at efficiencies exceeding 22%. One of the goals of solar cell research is to achieve efficiencies of over 30% at reasonable production costs.
CIGS thin-film technology presents a competitive alternative for standalone solar cells, with the added advantage of being applicable in other scenarios such as the bottom cell in tandem solar cell configurations.
In CIGS solar cells, the light-absorbing material is based on chalcopyrite, composed of copper (Cu), indium (In), gallium (Ga), and selenium (Se), hence the abbreviation CIGS, with the addition of silver and sodium.
To enhance the efficiency of electron separation, this layer undergoes rubidium fluoride treatment and is then placed between a transparent glass panel and a metal molybdenum backplate. The balance between sodium and rubidium, two alkali metals, and the composition of the CIGS layer are crucial for conversion efficiency.
To achieve this, researchers introduced a higher proportion of silver into the CIGS layer and achieved a "hockey stick" distribution of gallium, with higher concentrations near the backplate and lower, stable concentrations closer to the buffer layer of the cell. This distribution minimizes lateral and depth variations in bandgaps, reducing open-circuit voltage losses and thus achieving a new record efficiency of 23.64%.
The study provides comprehensive material and electrical analyses of the solar cells, comparing them with previous records in the same category.
"These analyses hopefully lay the groundwork for further improvements in cell performance. For the CIGS technology known for its high reliability, this new record suggests it could provide a viable alternative for new applications such as tandem solar cells," said Marika Edoff, Professor of Solar Cell Technology at Uppsala University, who led the research.
Related Paper: https://doi.org/10.1038/s41560-024-01472-3
