Replacing the fullerene layer in perovskite solar cells with an ionic salt significantly improved their performance, efficiency, and durability, according to a global research team led by the National Renewable Energy Laboratory (NREL). The findings were published in Science.
Perovskite solar cells use a crystalline semiconductor structure known for its high sunlight absorption and efficiency. However, long-term stability remains a key challenge.
The NREL-led team addressed this by altering the electron transport layer, which moves sunlight-triggered electrons through the cell to generate electricity. Traditionally, this layer uses fullerene (C60), but its weak molecular interface limits performance and stability.
To improve it, researchers introduced an ionic salt called CPMAC by chemically modifying C60. This change tripled the mechanical strength of the transport layer, boosting the cell’s durability.
The modified cells reached a lab-record efficiency of 26.1%, compared to 25.5% for traditional C60-based cells. They also demonstrated better thermal stability:
- 26% efficiency with 2% degradation after 2,100 hours at 65°C
- 25.5% efficiency with 5% degradation after 1,500 hours at 85°C
A small solar minimodule (6 cm², four subcells) showed 23% efficiency with under 9% degradation after 2,200 hours at 55°C.
The work was supported by the U.S. Department of Energy and involved researchers from NREL, King Abdullah University of Science and Technology, Newcastle University, CubicPV Inc., the University of Colorado Boulder, Arizona State University, and the University of Toledo.
