
Six junction solar cell reaches 47 per cent efficiency
Scientists at the National Renewable Energy Laboratory (NREL) in the US have built a solar cell with a record efficiency approaching 50 per cent.
The six-junction solar cell now holds the world record for the highest solar conversion efficiency at 47.1 per cent, which was measured under concentrated illumination. A variation of the same cell also set the efficiency record under one-sun illumination (or normal conditions) at 39.2 per cent.
“This device really demonstrates the extraordinary potential of multijunction solar cells,” said John Geisz, a principal scientist in the High-Efficiency Crystalline Photovoltaics Group at NREL and lead author of a new paper on the record-setting cell.
The paper, “Six-junction III-V solar cells with 47.1% conversion efficiency under 143 suns concentration,” appears in the journal Nature Energy.
To construct the device, NREL researchers relied on III-V materials. Each of the cell’s six junctions (the photoactive layers) is specially designed to capture light from a specific part of the solar spectrum. The device contains about 140 total layers of various III-V materials to support the performance of these junctions. The high cost means these III-V solar cells are most often used to power satellites where concentrated sunlight is more available.
Each junction contains a window layer, n-type emitter, unintentionally doped (UID) layer, ptype base, and back-surface field (BSF). Each junction layer is a few microns thick, using mixtures of gallium, indium,phosporus, selenium and GaAs.
On Earth the six-junction solar cell is well-suited for use in concentrator photovoltaics, said Ryan France, co-author and a scientist in the III-V Multijunctions Group at NREL.
“One way to reduce cost is to reduce the required area,” he said, “and you can do that by using a mirror to capture the light and focus the light down to a point. Then you can get away with a hundredth or even a thousandth of the material, compared to a flat-plate silicon cell. You use a lot less semiconductor material by concentrating the light. An additional advantage is that the efficiency goes up as you concentrate the light.”
France described the potential for the solar cell to exceed 50 per cent efficiency as “actually very achievable.” Dual junction silicon and tandem perovskite solar cells are currently at 28 per cent efficiency.
Geisz said that currently the main research hurdle to exceeding 50 per cent efficiency is to reduce the resistive barriers inside the cell that impede the flow of current. Meanwhile, he notes that NREL is also heavily engaged in reducing the cost of III-V solar cells, enabling new markets for these highly efficient devices.
Related solar cell articles
- GRAPHENE TANDEM PEROVSKITE CELL TAKES EFFICIENCY OVER 26 PER CENT
- PEROVSKITE THIN FILM CELL TAKES ON MAINSTREAM SOLAR PANELS
- INK-JET PRINTED PEROVSKITE SOLAR PANEL REACHES RECORD EFFICIENCY
- JINKOSOLAR SHRUGS OFF THE EFFECT OF CORONAVIRUS AS IT MOVES TO MONOCRYSTALLINE SOLAR MODULE PRODUCTION
