Researchers have created photovoltaic (PV) cells designed like LEDs to emit light as well as absorb it.
The counterintuitive concept actually increases voltage and efficiency, according to the team at University of California, Berkeley, who worked with Alta Devices to produce a prototype.
PV cells produce electricity when photons from the sun hit the semiconductor, knocking electrons loose to flow free.
But this can also generate new photons, in a process called luminescence. The idea behind the new design is that these extra photons — which do not come directly from the sun — should be allowed to escape from the cell as easily as possible.
This has the effect of increasing the voltage that the cell is able to produce, leading to a new prototype with an efficiency of 28.3 per cent, up from the previous record for single-junction cells of 26 per cent.
‘Fundamentally, it’s because there’s a thermodynamic link between absorption and emission,’ said Owen Miller of UC Berkley.