November 9 (SeeNews) - US scientists have designed a perovskite solar cell that achieves an average steady-state efficiency of 18.4%, with a high of 21.7% and a peak efficiency of 26%.
The scientists at the University of California, Berkeley and Lawrence Berkeley National Laboratory use a new technique to sandwich two types of perovskite into a single photovoltaic (PV) cell. The two perovskite solar cell materials, each tuned to absorb a different wavelength or color of sunlight, are combined into one "graded bandgap" solar cell that, the researchers say, absorbs nearly the entire spectrum of visible light. They have succeeded in mating the two materials thanks to using a single-atom thick layer of hexagonal boron nitride between the perovskite layers.
"The efficiency is higher than any other perovskite cell – 21.7 percent – which is a phenomenal number, considering we are at the beginning of optimizing this," said Alex Zettl, senior author of the paper that was published online on Monday.
The perovskite/boron nitride sandwich is placed atop a lightweight aerogel of graphene that, among other things, serves as a moisture barrier. The cell is then capped at the bottom with a gold electrode and at the top by a gallium nitride layer that collects the electrons that are generated within the cell, the scientists explain.
Perovskite is a promising, inexpensive material for photovoltaics. The UC Berkeley and Berkeley Lab scientists see the first perovskite solar cells potentially going on the market next year. Their cell design is described as a "major advance" in the field.