Hole-Transport Material Advances Perovskite PV Systems

A solar panel material has achieved 20.2 percent power-conversion efficiency while reducing the costs of photovoltaic systems.

A 3D illustration of fluorine-dithiophene molecules on a surface of perovskite crystals. Courtesy of Sven M. Hein/EPFL.

Perovskite materials have become popular for light-harvesting films. However, they require expensive hole-transporting materials whose function is to move positive charges generated when light hits the perovskite film.

Now, a research team at the Swiss Federal Institute of Technology in Lausanne (EPFL) has engineered a hole-transporting material that costs only a fifth of the two existing material options, and offers an improved efficiency of 20.2 percent.

EPFL developed a molecularly engineered hole-transporting material: a simple dissymmetric fluorine-dithiophene (FDT). FDT can be easily modified, according to the researchers, meaning it could act as a blueprint for the next generation of low-cost hole-transporting materials.

"The best performing perovskite solar cells use hole transporting materials, which are difficult to make and purify, and are prohibitively expensive, costing over €300 per gram, preventing market penetration," said professor Mohammad Nazeeruddin. "By comparison, FDT is easy to synthesize and purify, and its cost is estimated to be a fifth of that for existing materials — while matching, and even surpassing their performance."

The research was published in Nature Energy (doi: 10.1038/nenergy.2015.17).