Record 25.14% efficiency for perovskite/CIGS tandem cell

Perovskite-CIGS tandem solar cell achieve record 25.14% efficiency at Tokyo City University Japan

Researchers at Tokyo City University in Japan have reportedly achieved a new world record power conversion efficiency for a tandem solar cell which combines a perovskite top cell with a copper-indium-gallium-selenide (CIGS) bottom cell. The two-terminal device has an active area of 1 cm² and reached a certified efficiency of 25.14%. The result was certified by Japan’s National Institute of Advanced Industrial Science and Technology (AIST). Researchers in Japan claim to have achieved a world record power conversion efficiency for a tandem solar cell based on a top perovskite device and a bottom cell based on copper, indium, gallium and selenium (CIGS). They said further efficiency improvements can be expected by optimizing the cell configuration to improve the short-circuit current. In addition, they aim to accelerate research and development toward practical application through improvements in additives and passivation technology, with no further technical details of the new cell design being revealed.

This surpasses the previous record of 24.6% for a perovskite-CIGS tandem, which was set by Germany’s Helmholtz-Zentrum Berlin (HZB) in February 2025, after which groups worldwide had been trying to push the technology beyond the 25% threshold. The Japanese team notes that, until now, this 25% mark had remained out of reach despite intensive international research efforts. The tandem device has a two-terminal (2T) configuration, an active area of 1 cm2, and an certified efficiency of 25.14%.  “Since then, improvement research has been conducted around the world, but the 25% barrier had not been broken,” the Japanese team stated. The layer promotes better crystallinity of the perovskite film by providing a more suitable growth surface. At the same time, it reduces interfacial recombination losses which would otherwise lower device efficiency. It also prevents unwanted chemical reactions between the CIGS layer and perovskite precursors.

The new record cell is built on a CIGS bottom device originally developed at AIST, paired with a perovskite top cell which uses an improved absorber layer with higher crystallinity. This enhancement is enabled by a newly introduced interfacial barrier layer between the two subcells, which provides a more favorable surface for perovskite growth, suppresses interfacial recombination losses, and blocks undesirable chemical reactions between the CIGS absorber and the perovskite precursor materials. The top cell was built with a substrate made of indium tin oxide (ITO), a self-assembled monolayer (SAM) known as MeO-2PACz, the perovskite absorber, an electron transport layer (ETL) relying on buckminsterfullerene (C60) and tin dioxide layer deposited via atomic layer deposition (ALD-SnO2), another ITO layer, an antireflective coating made of magnesium fluoride (MgF2), and silver metal contact.

The scientists explained that the cell is based on bottom CIGS device developed by AIST itself and top perovskite cell with an improved perovskite absorber with higher cristallinity, which was achieved via a new barrier layer placed between the two cells. In the top perovskite cell, the researchers employed an indium tin oxide (ITO) substrate, a MeO-2PACz self-assembled monolayer (SAM), the perovskite absorber, and an electron transport stack consisting of buckminsterfullerene (C60) and an atomic-layer-deposited tin dioxide (ALD-SnO₂) layer, followed by an additional ITO layer, a magnesium fluoride (MgF₂) antireflection coating, and a silver contact. The CIGS bottom cell uses soda-lime glass (SLG) as the substrate, a molybdenum (Mo) back contact, the CIGS absorber layer, a cadmium sulfide (CdS) buffer, and a zinc oxide (ZnO) window layer. Tested under standard illumination conditions, the tandem cell achieved an efficiency of 25.14%.

Under standard test conditions, the tandem device delivered not only 25.14% efficiency but also an open-circuit voltage of 1.845 V, a short-circuit current density of 16.25 mA/cm², and a fill factor of 83.5%. The team expects that further gains are possible by refining the device architecture to increase the short-circuit current, and they plan to speed up development toward practical applications through improved additives and passivation strategies, although detailed information on these aspects has not yet been disclosed. We have to wait for final outcome in near future.