Chinese scientists develop strategy to improve flexible tandem solar cell performance

BEIJING -- Chinese scientists have found a way to make flexible tandem solar cells more efficient and durable by enhancing the adhesion of top layers to the bottom layers of the cell, according to a recent research article published in the journal Nature Energy.

Copper indium gallium selenide (CIGS) is a commercial semiconductor known for its outstanding adjustable bandgap, strong light absorption, low-temperature sensitivity and superior operational stability, making it a promising candidate for bottom-cell use in next-generation tandem solar cells.

Flexible perovskite/CIGS tandem solar cells combine a top layer of perovskite, a material that efficiently converts sunlight into electricity, with a bottom layer of CIGS. As a result, this tandem cell holds great potential for lightweight, high-efficiency applications in the photovoltaic field.

However, the rough surface of CIGS makes it difficult to produce high-quality perovskite top cells — which limits the commercial prospects of these tandem cells.

Notably, researchers from the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences have developed an innovative antisolvent-seeding strategy to enhance the performance of perovskite top cells on rough surfaces.

Based on this strategy, the team fabricated a flexible monolithic perovskite/CIGS tandem solar cell measuring 1.09 square centimeters. Competing with top rigid counterparts, this device achieved an impressive stabilized efficiency of 24.6 percent (certified at 23.8 percent) — one of the highest reported values for flexible thin-film solar cells to date.

After 320 hours of operation and 3,000 bending cycles at a radius of one centimeter, the device retained over 90 percent of its initial efficiency, demonstrating exceptional mechanical durability and long-term stability.