NREL and UNSW raise two-junction solar cell efficiency record to 32.9%
The US Department of Energy’s National Renewable Energy Laboratory (NREL) and the University of New South Wales (UNSW) in Australia have achieved record energy conversion efficiency for two-junction solar cells, creating a cell with two light-absorbing layers that converts 32.9% of sunlight into electricity (Myles A. Steiner et al, ‘High Efficiency Inverted GaAs and GaInP/GaAs Solar Cells With Strain‐Balanced GaInAs/GaAsP Quantum Wells’, Advanced Energy Materials, 13 December 2020).
Key to the cell’s design is a series of more than 150 ultrathin layers of alternating semiconductors that create quantum wells in the cell’s bottom absorber, allowing it to capture energy from a key range of the solar spectrum. While the new record only improves modestly on the previous 32.8% efficiency record, it is the first record-efficiency multi-junction solar cell to use a strain-balanced structure — a design that holds promise for further improvements.