Scientists with Berkeley Lab and the University of Illinois combined quantum dot light emitters with spectrally matched photonic mirrors to create blue light collecting solar cells. These special solar cells reportedly collect blue photons at 30 times the concentration of conventional solar cells, the highest luminescent concentration factor ever. The scientists contend that this development may lead to the low-cost solar cells utilize the high-energy part of the solar spectrum efficiently.
Berkeley Lab director Paul Alivisatos who led the research pointed out that they also achieved an optical efficiency of 82-percent for blue photons. Alivisatos and Ralph Nuzzo of the University of Illinois are two of the authors of a paper in ACS Photonics describing the development.
An LSC (luminous solar concentrator) employs a process called Stokes shift to absorb the light on a plate embedded with highly efficient light emitters called “lumophores”. The lumophores re-emit the absorbed light at longer wavelengths, and an inexpensive waveguide directs the re-emitted light to a micro-solar cell, which converts it to electricity. The plate is much larger than the micro-solar cell. So, the light is highly concentrated.
The micro-solar cell uses only small amounts of expensive III−V photovoltaic materials. Previously, parasitic losses have limited the concentration factor and collection efficiency of the molecular dyes that were used as lumophores.
“We replaced the molecular dyes in previous LSC systems with core/shell nanoparticles composed of cadmium selenide (CdSe) cores and cadmium sulfide (CdS) shells that increase the Stokes shift while reducing photon reabsorption,” Bronstein said.
Berkeley Lab, he National Renewable Energy Lab (NREL), the University of Illinois, and Caltech have begun partnering on a new DOE solar concentrator project called MOSAIC because of the success of the LSC. MOSAIC stands for Micro-scale Optimized Solar-cell Arrays with Integrated Concentration.