Scientists at the Lawrence Berkeley National Laboratory and the University of Illinois have made solar cells that collect blue photons at 30 times the concentration of conventional solar cells. This paves the way for the development of low-cost solar cells that efficiently use this high-energy part of the solar spectrum.
Conventional solar cells directly absorb sunlight and convert it into electricity; luminescent solar concentrators (LSCs), on the other hand, absorb the light on a plate embedded with highly efficient light-emitters called “lumophores”. These then re-emit the absorbed light at longer wavelengths, a process known as the Stokes shift. This re-emitted light is directed to a micro-solar cell which converts it into electricity.
Because the plate is much larger than the micro-solar cell, the solar energy hitting the cell is highly concentrated. So only small amounts of expensive photovoltaic materials are needed to collect light from an inexpensive luminescent waveguide.
The scientists replaced the molecular dyes used in previous LSC systems with nanoparticles composed of cadmium selenide cores and cadmium sulfide shells. These increase the Stokes shift while reducing photon re-absorption yielding LSCs that collect blue photons at 30 times the concentration of conventional solar cells.
The researchers believe that they will be able to achieve even higher concentration ratios through improvements to the luminescence quantum yield, waveguide geometry, and photonic mirror design.