I am trying to calculate the recombination coefficients from the light-intensity-dependent Voc measurement. When I fitted the measured results following the equation Voc = (2kB*T/q)*ln[k1*(1+k2*G)0.5-1], the fitting result is good. kB, T, q, and G are the Boltzmann constant, temperature, electron charge, and average generation rate. k1 and k2 are the fitting parameters.
However, there is still a question of how to calculate the average generation rate from the illumination intensity. Because the illumination unit is ‘sun’ or ‘power’, but the unit of the average generation rate is cm-2 s-1.
In the research paper, k2 = 45 sun-1, and then it directly presents the result that k2 = 6.4 * 10-21.
Hej Yao.
I am sure this will help:
https://www.pveducation.org/pvcdrom/pn-junctions/generation-rate
First, you need the photon flux No in cm-2s-1. Then you may assume an average absorption coefficient alpha and integrate No*alpha*exp(-alpha*x) from x=0 (surface) to W (absorber thickness). This will give you the average Generation rate. If you have alpha(lambda) data, you may additionally integrate over all wavelengths...
if you assume complete absorption A=1 and you know the bandgap, then you can also just cut the photon flux at the band gap value and have the generation rate when you correct for the absorber thickness. So, to get to the unit cm with a 1µm thick absorber you need to multiply the photon flux in cm-2s-1 by 1e4 to get to a G in cm-3s-1.
Best wishes,
Jan.
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