Band Gap Solar Panels

The optical band gap see below determines what portion of the solar spectrum a photovoltaic cell absorbs.

Band gap solar panels.

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. 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. A semiconductor will not absorb photons of energy less than the band gap. Actually the energy converted is the energy corresponding to the band gap.

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. Photons with more energy than necessary to separate an electron pair do generate an electron and a hole with the balance of their enegy being dissipated in the form of heat. Rest of the photon energy is simply a waste in the solar cell as heat. 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. The band gap is the minimum amount of energy required for an electron to break free of its bound state. Therefore increasing the temperature reduces the band gap. 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 2 falling on an ideal solar cell only 33 7 of that could ever be turned into electricity 337 w m 2. Band gap energy differs from one material to another. Lower energy is therefore needed to break the bond. Photons with energy less than the band gap will not separate electron pairs and simply pass through the solar cell.

It has been estimated that about 1 1 loss occurs for every 1 c rise in temperature of the cell. 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. Limiting efficiency of solar cells solar cells operate on. And the energy of the electron hole pair produced by a photon is equal to the bandgap energy.