Solar PV R&DProject Improved PV Energy Conversion
A report on how the process of photochemical upconversion could be applied to solar cells, in order to boost their light harvesting efficiency.
The solar cells that one sees going about everyday activities are made of silicon, and have a single energy threshold. Such cells do not absorb particles of light (photons) with an energy below about 1.1 electron‐ volts (eV, the energy it takes to move an electron across a voltage of 1.1 volts). The entire visible spectrum spans 1.6‐3.0 eV, and so silicon solar cells can make use of these photons, and part of the infrared spectrum. However, whether they absorb a red (2 eV) or blue (3 eV) photon, they will only use 1.1 eV of the energy, their energy threshold, or band‐gap. These limitations, missing the photons below the band‐gap, and wasting the portion of energy above the band‐gap, limit the energy conversion efficiency of a single‐ threshold silicon solar cell to about 30%.
Australian researchers have pushed silicon to exceed 25% efficiency, which approaches the fundamental limitation – the silicon ceiling. To push through the silicon ceiling, one requires better usage of the solar spectrum.