A single molecule boosts perovskite solar cell efficiency and lifespan

A new study in Science shows that the incorporation of a synthetic molecule into the design enhances the energy efficiency and longevity of perovskite solar cells. The benefits of the molecule, known as CPMAC, were found through an international collaboration that included King Abdullah University of Science and Technology (KAUST).   

CPMAC is an abbreviation for an ionic salt synthesized from buckministerfullerene, a black solid made of carbon atoms known as C60. Perovskite solar cells are typically made with C60, which has contributed to record energy efficiency. While preferred, C60 also limits the performance and stability of the solar cells, leading scientists to explore alternative materials.  

"For over a decade, C₆₀ has been an integral component in the development of perovskite solar cells. However, weak interactions at the perovskite/C₆₀ interface lead to mechanical degradation that compromises long-term solar cell stability. To address this limitation, we designed a C₆₀-derived ionic salt, CPMAC, to significantly enhance the stability of the perovskite solar cells," explained Professor Osman Bakr, Executive Faculty of the KAUST Center of Excellence for Renewable Energy and Sustainable Technologies (CREST), who led the KAUST contributions to the research.  

The chemistry of CPMAC improved the electronic properties of the solar cells. Cells with CPMAC had a power conversion efficiency – a standard metric used to evaluate the energy efficiency of solar cells – that was 0.6% higher than solar cells built with C60.  

If the average power plant produces 1 gigaWatt of power, then less than a 1% difference would still be enough to power 5,000 extra homes.  

"When we deal with the scale of a typical power station, the additional electricity generated even from a fraction of a percentage point is quite significant," said Hongwei Zhu, a research scientist at KAUST who also contributed to the study.  

Furthermore, CPMAC solar cells showed a drop in their power conversion efficiency that was one third that of C60 solar cells when the two types were exposed to hot temperatures at different humidities for over 2,000 hours, a benchmark for testing the stability of solar cells.  

The difference between the two types became more apparent upon assembling them into modules consisting of four solar cells, a simplified model of a solar panel, which generally consists of somewhere between 50 to 100 cells. 

These benefits were attributed to CPMAC reducing defects in a key component of the solar cell known as the electron transfer layer by creating ionic bonds with the perovskite rather than the weaker van der Waals bonds made with C60.