A team of researchers from the National University of Singapore, Empa Materials Science and Technology, and Helmholtz Institute Erlangen-Nürnberg for Renewable Energy claimed to have achieved a record efficiency of 29.9% for a semi-transparent perovskite cell.

The team paired the perovskite cells with a copper indium gallium diselenide (CIGS) bottom cell, allowing for their wider commercialization.

In the past, electrical and optical losses have limited the performance of wide-band-gap perovskite semi-transparent solar cells and reduced their widespread commercial usage. This prompted the researchers to attempt to maximize the performance of perovskite front cells.

Published in ScienceDirect, the research states how efficient thin-film tandems possess a huge potential for applications in building-integrated photovoltaics, transportation (such as vehicles and drones), and agrivoltaics, where efficiency, lightweight, and flexibility are important metrics.

The rough surface of CIGS requires special coating methods to enhance perovskite absorber quality and mitigate recombination losses. While the complex flattening process enhanced efficiency, it made the production of perovskite or CIGS less cost-effective.

With the new method, the scientists mechanically stacked the perovskite top cell and the CIGS bottom cell, making the two optically coupled but electrically independent. This leaves no room for interaction between the perovskite layer and the reactive layers in the bottom cell, allowing for greater design flexibility.

The team introduced new electrical and optical techniques, using ‘methyldiammonium diiodide’ and adjusting the optical interference spectrum.

This helped achieve a record efficiency of 20.2% (21.8% by J-V scan) for a semi-transparent perovskite cell and 81.5% average near-infrared transmittance. When paired with a CIS bottom cell, the tandem efficiency reached 29.9%.

As the two cells will be processed separately, this simplifies the manufacturing process, resulting in lower capital costs and faster market entry and, thus, easing the commercialization process. Their commercial viability study also demonstrated that the perovskite/CIGS 4T thin-film tandem can achieve a cost-competitive scenario despite its higher manufacturing cost due to its high energy yield potential.

The research presents several opportunities for diversifying thin-film-based perovskite or CIS tandem cells.

The findings come on the heels of a discovery earlier this year, where researchers found a low-cost and scalable carbon ink formulation that can enable scalable manufacturing of perovskite solar cells.

In 2022, researchers in Germany also achieved 22.5% efficiency in perovskite-silicon tandem solar cells, enabling the likely industrial-scale production of these cells.