Hi, I've been wrestling with this question off and on for a while. I recall reading in the past that a Schottky junction has a upper limit in Voc close to Eg/2 but I can't seem to remember the reference or find other references to support this. Does anyone have a good explanation for limits for Voc in a Schottky vs a PN juntion? Do both have the same upper bound thermodynamic limit (i.e. Shockley–Queisser)?
Again I will answer this question in terms of general background about semiconductor device perspective. According to Barden’s approximation If we assumes that solar cell is made from Schottky structure and silisyum based then automatically we have to accept Voc value could extend up to 2/3 times of forbidden band gap potential value of the semiconductor material.
If we assumes that solar cell is made from homojunction structure and silisyum based then automaticall we have to accpet that Voc value could extend up to forbidden band gap potenatial value of the semiconductor material.
Dear Kyle,
Adding to the above answer of Abdulkadir,
The open circuit of a single junction solar cell is given by:
V0c= n Vt log ( Iph / I0),
n is the ideality factor, Vt the thermal voltage, Iph is the photo generated current and I0 the reverse saturation current. So for the external quantum deficiency the Iph will be equal for the two types of the cells. Then the main difference lies in the reverse saturation current. The nature of the reverse saturation current is different in the two cells. In the SB cell I0 is limited by majority carrier flow of the potential barrier from the semiconductor to the metal while the reverse saturation current in the pn junction is limited by the diffusion of minority carrier across the junction. So, normally the reverse saturation current of the SBSC is larger that that of the p-n SC. And consequently the open circuit voltage of the latter is greater than the former.
However, some basic structural changes were made for the SBSC to approach that of the p-n SC by introducing an i layer to suppress the majority carrie current between the metal and the semiconductor such that ultimately one forms the so called induced n-p junction and in this way the they approach each other. The achieved open circuit voltage is slightly larger than Eg/2 fo silicon.
For more information please follow the link:http://sjbyrnes.com/NSE290-FinalPaper.pdf
wish you success
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