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MIT Breaks Theoretical Efficiency Limit of Solar Cells


MIT-solar-cell-efficiencyAn MIT demonstration revealed the ability to top the theoretical upper limit of solar cell efficiency which is currently 32 percent.

It was a silicon solar cell that showed that the Shockley-Quiesser Limit could be bypassed, suggesting a silicon alternative to perovskites and other solar cell types.

An efficiency of 32 percent is considered high, being that it is difficult for solar systems to maintain high heat as well as utilize an optical filter proficient at filtering out undesired wavelengths. Attempts at moving beyond this maximum have been a struggle.

Although results showed an efficiency of 6.8 percent and that the demonstration was in its early stage, the researchers seemed to think their standards for the sake of working towards breaking the Shockley-Quiesser Limit had been met.

One of the researchers David Bierman stated, ““…This is the first time we’ve actually put something between the sun and the PV cell to prove the efficiency” of the thermal system. Even with this relatively simple early-stage demonstration, Bierman says, “we showed that just with our own unoptimized geometry, we in fact could break the Shockley-Queisser limit.”

Thermophotovoltaics, the process of converting heat into electricity through photons, is the solar cell’s method of operation. Special materials trap heat supplied from the sun and prevent the heat from reaching the solar cell at first. The materials are made of nanophotonic crystals as well as vertically aligned carbon nanotubes.

Carbon nanotubes are used because the entire color spectrum can be captured through the solar cell to generate thermal radiation. This type of radiation, which encompasses the heat, is turned into wavelengths needed by the photovoltaic material.

It might be some time before the silicon solar cell reaches the market, but the possibility of bypassing the Shockley-Quiesser Limit under normal circumstances makes the wait worth it.


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