The Shockley Queisser limits the efficiency of single junction solar cells and sets the maximum efficiency for Si solar cells at about 30%. The limit is imposed because of two constraints. First, the energy a solar cell generates from each conversion event is approximately maximized by its bandgap, irrespective of the incoming photon energy. Thus, energetic photons lose most of their energy to heat in the solar cell. Second, a solar cell cannot harness photons at wavelengths longer than its bandgap. Therefore, splitting of energetic photon to two Near-IR (NIR) photons doubles the quantum efficiency and the output energy a PV delivers. Also the fusion of two NIR photons below the bandgap of PV to generate one photons accessible for the PV (energy above the PVs bandgap) bust the potential efficiency of PV above Shockley Queisser limit.
Nonlinear optics (NLO) offers efficient frequency conversion. Yet, it cannot contribute to PVs due to operation limits at high intensity and coherence, much above the solar radiation. Solar powered lasers allows to increase intensity and coherence by orders of magnitude, thus it is the missing link between PVs and NLO. But thus far, power threshold of solar laser is above 2000 suns , making it inapplicable for PVs. Here I propose to build solar powered laser at low solar concentration (below 2 suns), which will open the field of NLO for PVs. This proposal is based on my recent experimental demonstration , which enables the reduction of current power threshold of incoherently pumped laser by three orders of magnitude. In addition to PVs, this research opens the way to new high power lasers, and many on-chip applications in spectroscopy, sensing, and communication.
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