Development of new, highly efficient bifacial solar cells

Copper indium gallium selenide (CIGS) solar cells with a metallic back contact have achieved an impressive efficiency of 23% and demonstrated excellent stability. CIGS technology is very promising for further development and improvement. The EU-funded Hi-BITS project aims to develop a groundbreaking device structure that incorporates both photon recycling and high bifaciality. This innovative structure is expected to increase the efficiency of CIGS to a remarkable 25%. On this basis, the project will develop four new applications that leverage the advantages of bifaciality and other integrated features to further increase efficiency. In addition, Hi-BITS will work to improve existing components to increase overall efficiency, making these solar cells well suited for various applications, including building integration, vehicles, and agriculture.

Project plan

CIGS solar cells currently achieve an efficiency of 23% with a metallic back contact and an absorber layer >2 m thick, as well as excellent stability. The Hi-BITS partners will introduce a disruptive device structure that enables a high degree of bifaciality and photon recycling. Efficiency will be improved to over 25% thanks to innovative high-quality CIGS absorbers and passivation at the back contact, which eliminates composition gradients and reduces absorber thickness. Hi-BITS will explore four different applications that leverage all of these characteristics, including bifaciality, flexibility and reflectivity, semi-transparency, and suitability for tandems. While bifaciality captures scattered light reflected from the ground, thereby increasing annual yield, reflectivity and flexibility enable photon recycling for lightweight modules. The required back reflector can be easily integrated into the bifacial Hi-BITS cells. To close the efficiency gap between large-area modules and record-breaking cells, Hi-BITS will improve monolithic integration to increase the productive area of the module, as well as semiconductor quality through rapid feedback methods suitable for industrial processes. The applications envisaged as a result of Hi-BITS meet market requirements and are particularly well suited for integration into buildings or vehicles, or for agricultural photovoltaics. Modules for these new applications will be tested outdoors in three different European climate zones to demonstrate higher energy yield and stability. Life cycle analyses and cost calculations taking into account circular economy aspects will highlight the superior sustainability of these new modules. Hi-BITS involves five European PV manufacturers and will improve a technology that does not depend on imports of ingots or wafers, thereby strengthening the European PV value chain. The results will advance thin-film manufacturing through higher efficiency, lower raw material consumption, shorter and well-controlled processes, better module technologies, and novel applications.

Start date: October 1, 2023

End date: September 30, 2026