Photovoltaic cell gap
In , the radiative efficiency limit (also known as the detailed balance limit, Shockley–Queisser limit, Shockley Queisser Efficiency Limit or SQ Limit) is the maximum theoretical using a single to collect power from the cell where the only loss mechanism is radiative recombination in the solar cell. It was first calculated by and This required amount of energy to excite an electron is defined as band gap. Band gap is an intrinsic property of semiconductors and eventually has a direct influence on the photovoltaic cell voltage. [pdf]
FAQS about Photovoltaic cell gap
What is a band gap in a solar cell?
The band gap represents the minimum energy required to excite an electron in a semiconductor to a higher energy state. Only photons with energy greater than or equal to a material's band gap can be absorbed. A solar cell delivers power, the product of current and voltage.
What happens if the band gap of a PV cell is too small?
At the same time, if the band gap of the PV material is too small compared to the incident photon energy, a significant amount of energy will be converted to heat, which is not a good thing for PV cell itself. No matter how much higher the photon energy is compared to the band gap, only one electron can be freed by one photon.
Why do photovoltaic cells have a limited efficiency?
No matter how much higher the photon energy is compared to the band gap, only one electron can be freed by one photon. This is the reason for the limited efficiency of the photovoltaic cells. The data in Figure 4.2 show how the maximum efficiency of a solar cell depends on the band gap.
What is a good band gap for a photovoltaic material?
The ideal photovoltaic material has a band gap in the range 1–1.8 eV. Once what to look for has been estab-lished (a suitable band gap in this case), the next step is to determine where to look for it. Starting from a blank canvas of the periodic table goes beyond the limitations of present human and computational processing power.
How do you determine a material's promise in photovoltaics?
If one were to choose a single parameter to perform a first screen to determine a material’s promise in photovoltaics, it would be its band gap. The band gap represents the minimum energy required to excite an electron in a semiconductor to a higher energy state.
How does a solar cell work?
Only photons with energy greater than or equal to a material’s band gap can be absorbed. A solar cell delivers power, the product of cur-rent and voltage. Larger band gaps produce higher maximum achievable voltages, but at the cost of reduced sunlight absorption and therefore reduced current.
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