It is well known that in case of a solar cell the open circuit voltage is limited by the band gap of the material. But in case of hetero structure solar cell what happens to this criteria. Is it possible to cross the band gap of the material in case of a hetero structure solar cell. or is there any other technique available to do so?
Dear Girija,
welcome,
A heterojunction solar cell is composed of two semiconductor materials. One is the absorber which has the lower bandgap and the window emitter layer which has a widebandgap to allow the passage of lower wavelengths of the incident solar radiatio to pass to the absorber layer. So from the conceptual point of view the open circuit voltage is limited by the bandgap lower band gap material.
If the heteroface is ideal then the reverse saturation current will be smaller than the homojunction solar cells made solely from the absorber material.
This leads to an increase in the opencircuit voltage compared to homojunction from the absorber.
To increase the open circuit voltage one would increase the energy gap of the absorber. This has been really observed. But unfortunately increasing the bandgap beyond certain value the photoconversion efficiency of the solar cell will decrease. So, there is an optimum bbandgap which is about 1.35 eV.
Best wishes
Thanks Dr. Abdelhalim Zekry for your value able suggestion. One more thing will be help full for me if you share some thing about the thermodynamical efficiency limit of SJ hetero structure solar cell.
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