Germany's HZB Achieves 25.5% Efficiency Record for CIGS-Perovskite Tandem Solar Cell

en.Wedoany.com Reported - German researchers have achieved a power conversion efficiency record for a tandem solar cell combining a perovskite top layer and a copper indium gallium selenide (CIGS) thin-film bottom layer.

The research is part of the EU-funded "SOLMATES" project, led by the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), which aims to explore the integration of CIGS and perovskite technologies. HZB stated that the project's previous record was 24.6%.

HZB researcher Guillermo Farias Basulto said that to surpass the previous milestone, the team tested various cell structures based on continuous improvements, including CIGSe bottom cells with different bandgaps (1.05 eV and 1.1 eV) and two types of aluminum-doped zinc oxide with different thicknesses but similar properties.

To reduce interfacial recombination losses and improve device stability, the researchers screened multiple combinations of nickel oxide (NiOx) and self-assembled monolayers (SAMs) as hole transport layers. They also optimized the electron-selective contact process by adjusting the initial thermal evaporation rate of fullerene C60 (Buckminsterfullerene) on an ultra-thin 1 nm lithium fluoride passivation layer.

The record-breaking cell has an area of only 1.081 cm². SOLMATES researchers fabricated a mini-module using a similar material stack, achieving an efficiency of approximately 19.7% over an area of 2.25 cm².

Farias Basulto emphasized the potential of the experimental approach in achieving higher efficiencies, stating that the physics inherent in the current cell structure suggests that 25.5% is merely a stepping stone, as internal tests on similar structures have already reached an efficiency of 27.5%.