Berlin team sets new tandem solar cell record
The tandem solar cell combines CIGSe and perovskite semiconductors. It is slightly larger than 1 square centimeter and achieves a record efficiency of 25.5% for this combination of materials.
Berlin researchers have set a fresh benchmark for solar technology. A team from Helmholtz-Zentrum Berlin (HZB) and the Center for the Science of Materials Berlin (CSMB) at Humboldt-Universität zu Berlin combined a CIGS semiconductor layer with perovskite to convert 25.5 percent of sunlight into electricity, according to the HZB press release. That beats the previous record of 24.6 percent for the same material combination and cell size, and the result has now been certified and added to the Solar Cell Efficiency Tables, known in the industry as the Green Tables, the reference list used by the global photovoltaics community.
Getting into that particular table takes more than just a high efficiency number. Cells also need an area larger than 1 square centimeter, unlike other lists that track record efficiencies regardless of size.
To beat their own previous mark from the European SOLMATES project, the team tested CIGSe cells with two different bandgaps and varied the thickness of aluminum doped zinc oxide layers, while also trying out different cell architectures. Chemist Wuai Zhang worked through combinations of nickel oxide and self assembled monolayers to cut down energy losses at material interfaces and improve stability, and fine tuned how a fullerene layer was deposited on an ultra thin lithium fluoride coating.
The record cell measures 1.081 square centimeters. In a related project, researchers from HTW Berlin and HZB also built a mini module reaching close to 19.7 percent efficiency at 2.25 square centimeters.