What is the effect of the band structure on the Voc value of ternary planar heterojunction organic solar cells?
Dear W. Boukhili
Compared to single junction solar cells the multijunction solar cells are constructed from different energy gap semiconductors ramped from the smallest to largest energy gap with the smallest energy gap is the bottom cell
and the highest energy gap material is the top cell.So when the solar radiation falls on the multijunction cell, the top junction absorbs the shortest wavelength radiation and the cells in the middle absorbs the medium solar radiation and the bottom solar cells absorbs longest solar radiation. The multijunction solar cells are connected in series so in order to get the maximum output power one has to distribute the solar radiation amongst them such that their short circuit current must be equal.
The triple junction solar cell is a special case pf multijunction solar cells.
Since one has to distribute the radiation among the tandem multijunction cell then the shortcircuit current decreases as the number of the MJ cells increases.
As the cells are connected in series their opencircuit voltage sums up and increases with the number of tandem cells.
For one junction cell its open circuit voltage increases with its energy gap.
So, in summary the open circuit voltage will appreciable increases while the shortcircuit current decreases with much less ration than the increase in the open circuit voltage and hence the photoconversion efficiency appreciable increases with the increase of the number of the tandem cells.
The basic idea of the multijunction cell is to absorb more portion of the wide spectrum solar radiation.
Best wishes
Dear W. Boukhili
Compared to single junction solar cells the multijunction solar cells are constructed from different energy gap semiconductors ramped from the smallest to largest energy gap with the smallest energy gap is the bottom cell
and the highest energy gap material is the top cell.So when the solar radiation falls on the multijunction cell, the top junction absorbs the shortest wavelength radiation and the cells in the middle absorbs the medium solar radiation and the bottom solar cells absorbs longest solar radiation. The multijunction solar cells are connected in series so in order to get the maximum output power one has to distribute the solar radiation amongst them such that their short circuit current must be equal.
The triple junction solar cell is a special case pf multijunction solar cells.
Since one has to distribute the radiation among the tandem multijunction cell then the shortcircuit current decreases as the number of the MJ cells increases.
As the cells are connected in series their opencircuit voltage sums up and increases with the number of tandem cells.
For one junction cell its open circuit voltage increases with its energy gap.
So, in summary the open circuit voltage will appreciable increases while the shortcircuit current decreases with much less ration than the increase in the open circuit voltage and hence the photoconversion efficiency appreciable increases with the increase of the number of the tandem cells.
The basic idea of the multijunction cell is to absorb more portion of the wide spectrum solar radiation.
Best wishes
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