Perovskite-CIGS Tandem Sets New Efficiency Benchmark

Key takeaways:

• Tokyo City University achieved a record 25.14% efficiency for a perovskite-CIGS tandem solar cell

• The tandem structure combines 2 thin-film technologies, enabling lightweight and flexible PV applications

• A newly developed interface layer improved the crystallinity of the perovskite layer and supported higher device performance

Perovskite and tandem technologies have seen multiple developments over the past couple of years, especially for the latter, since the efficiency potential of a multi-junction cell is higher than that of a single-junction cell. Researchers from Tokyo City University recently announced a record-efficiency cell with a perovskite-CIGS tandem structure. CIGS stands for copper indium gallium selenide, which comes under the thin-film solar cell category, similar to perovskite.

There have been several efficiency records and process developments with perovskite-silicon tandem architectures, which were highlighted at the TaiyangNews Next-Generation PV Technology Conference 2026. A comparatively small community is also working on alternative tandem architectures, such as double perovskite-silicon, perovskite-perovskite, and perovskite-CIGS tandems.

As part of its research on perovskite-CIGS tandem, Tokyo University’s Advanced Research Laboratories has developed a perovskite-CIGS cell with 25.14% efficiency on a photosensitive area of 1 cm². The previous record holder for this type of cell was Helmholtz-Zentrum Berlin (HZB), with an efficiency of 24.6% achieved in early 2025.

This tandem combination offers flexibility, as both cells are thin-film-based and exhibit greater flexibility than crystalline silicon, opening up a wide range of curved-surface applications for these PV products.

The record efficiency was achieved by developing a new carrier recombination interface layer between the 2 cells. According to the press release, this layer acts as a barrier for the CIGS bottom cell and improves the crystallinity of the perovskite layer formed on top of it. However, the technical details of this layer are unknown at the time of writing.

The final tandem cell measured 4 µm in thickness, comprising a 3 µm CIGS cell and a 1 µm perovskite cell. The experiments in this study used glass as the substrate; however, the press release states that other compatible lightweight and flexible substrates can also be used. The research team highlights the scope for improvement in this tandem technology, with a focus on optimizing the perovskite and CIGS compositions. Additionally, the efficiency and durability of these cells are planned to be improved by enhancing passivation and additives used in the core materials.

The research was led by Prof. Ryosuke Ishikawa of Tokyo City University, in collaboration with Dr. Naogo Ishizuka, Principal Researcher at the National Advanced Research Laboratories of the National Institute of Advanced Industrial Science and Technology (AIST). The project was commissioned by the New Energy and Industrial Technology Development Organization (NEDO).