Wang Rui's team from the Future Industry Research Center and College of Engineering at Westlake University has made significant breakthroughs in the field of flexible tandem solar cells, successfully stacking perovskite with copper indium gallium selenide materials, resulting in a photoelectric conversion efficiency of 23.4%. The related research paper was recently published in Nature Photonics.

Flexible perovskite/copper indium gallium selenide tandem solar cells.

If single-junction perovskite solar cells are like a "single-layer cake," then tandem solar cells come in multi-layered flavors. Different flavors of cake layers correspond to different semiconductor material layers, each capable of "catching" sunlight of a specific wavelength. In this way, it can absorb a wider range of solar energy than "single-layer" cells, converting sunlight into electricity more efficiently, thus breaking the ceiling for single-junction solar cell conversion efficiency.

The team successfully layered perovskite with copper, indium, gallium, and selenide—two different flavors of the "cake". This flexible, thin, and lightweight multilayer solar cell is only as thick as a hair's diameter and is expected to be applied in the future to irregular surfaces such as buildings, automobiles, aircraft, and flexible wearable devices.