Band Gap Solar Panels

Band gap energy differs from one material to another.

Band gap solar panels.

The optical band gap see below determines what portion of the solar spectrum a photovoltaic cell absorbs. The inability to fully utilize the incident energy at high energies and the inability to absorb low energies of light represents a significant power loss in solar cells consisting of a single p n junction. In the bond model of a semiconductor band gap reduction in the bond energy also reduces the band gap. So the result is a loss in efficiency.

Solar cells with multiple band gap absorber materials improve efficiency by dividing the solar spectrum into smaller bins where the thermodynamic efficiency limit is higher for each bin. Any energy above the band gap energy is not utilized by the solar cell and instead goes to heating the solar cell. It has been estimated that about 1 1 loss occurs for every 1 c rise in temperature of the cell. Photons with energy less than the band gap will not separate electron pairs and simply pass through the solar cell.

Solar cells operate on. Traditional single junction cells with an optimal band gap for the solar spectrum have a maximum theoretical efficiency of 33 16 the shockley queisser limit. In a solar cell the parameter most affected by an increase in temperature is the open circuit voltage. And the energy of the electron hole pair produced by a photon is equal to the bandgap energy.

The band gap is the minimum amount of energy required for an electron to break free of its bound state. Lower energy is therefore needed to break the bond. Limiting efficiency of solar cells. The actual band gap for formamidinium fa lead trihalide can be tuned as low as 1 48 ev which is closer to the ideal bandgap energy of 1 34 ev for maximum power conversion efficiency single junction solar cells predicted by the shockley queisser limit.

This maximum occurs at a band gap of 1 34 ev. Therefore increasing the temperature reduces the band gap. Actually the energy converted is the energy corresponding to the band gap. The most popular solar cell material silicon has a less favorable band gap of 1 1 ev resulting in a maximum efficiency of about 32.

Rest of the photon energy is simply a waste in the solar cell as heat. When the band gap energy is met the electron is excited into a free state and can therefore participate in conduction. That is of all the power contained in sunlight about 1000 w m falling on an ideal solar cell only 33 7 of that could ever be turned into electricity 337 w m. A semiconductor will not absorb photons of energy less than the band gap.

The band gap determines how much energy is needed from the sun for conduction as well as how much energy is generated.