Overcoming theoretical limits on solar cell capacity

Subject: Science and tech

Section: Msc

Photovoltaics and solar cells:

Photovoltaics is a study focusing on the conversion of light energy into electrical energy.
Solar cells, which are key devices in photovoltaics, harness the energy from the Sun, Earth’s primary light and energy source.
Solar cells are comprised of semiconducting materials, such as doped silicon, that facilitate this energy conversion.

How Solar Cells Work:

Sunlight interacting with semiconductor sex cites electrons from a lower-energy valence band to a higher-energy conduction band, leaving behind a “hole” in the valence band.
A hole represents a vacant site with a positive charge due to the absence of an electron.
The transition of electrons and the creation of holes generate electron-hole pairs, essential for creating photocurrent in semiconductors.

The Shockley-Queisser Limit:

It is a theoretical concept that defines the maximum efficiency potential of a solar cell to produce electricity.
Named after Physicists William Shockley (U.S.) and Hans-Joachim Queisser (Germany).
Factors such as transparency loss (~25%) and thermalisation (~30%) limit the maximum efficiency of solar cells.
Modern solar cells convert only about a third of the incident solar energy into electrical energy.

Challenges and Innovations:

Semiconductors struggle to utilize photons with either insufficient energy to overcome the band gap or those with excess energy that merely heats the device.
Efforts to surpass the Shockley-Queisser limit include carrier multiplication (allowing a photon to create multiple electron-hole pairs) and hot carrier extraction (capturing high-energy photons before they convert to heat).
South Korean physicist Young Hee Lee highlights these methods as promising pathways to enhance solar cell efficiency.

Source: TH