(January 18, 2016) EPFL
scientists have developed a solar-panel material that can cut down on
photovoltaic costs while achieving competitive power-conversion efficiency of
20.2%.
Some of the most promising solar cells today use
light-harvesting films made from perovskites – a group of materials that share
a characteristic molecular structure. However, perovskite-based solar cells use
expensive “hole-transporting” materials, whose function is to move the positive
charges that are generated when light hits the perovskite film. Publishing in
Nature Energy, EPFL scientists have now engineered a considerably cheaper
hole-transporting material that costs only a fifth of existing ones while
keeping the efficiency of the solar cell above 20%.
As the quality of perovskite films increases, researchers
are seeking other ways of improving the overall performance of solar cells.
Inadvertently, this search targets the other key element of a solar panel, the
hole-transporting layer, and specifically, the materials that make them up.
There are currently only two hole-transporting materials available for
perovskite-based solar cells. Both types are quite costly to synthesize, adding
to the overall expense of the solar cell.
To address this problem, a team of researchers led by
Mohammad Nazeeruddin at EPFL developed a molecularly engineered
hole-transporting material, called FDT, that can bring costs down while keeping
efficiency up to competitive levels. Tests showed that the efficiency of FDT rose
to 20.2% – higher than the other two, more expensive alternatives. And because
FDT can be easily modified, it acts as a blueprint for an entire generation of
new 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,” says
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.”