On the collection of photocurrent in solar cells with a contact grid

Abstract

The exact solution for the dependence of specific power of photoconversion in the mode of maximum collected power on distance l between lines of the contact grid has been obtained. It is shown that in an optimized case, when the change of the potential of heavily doped front layer under contacts and between contacts is less than kT/q, the characteristic length L can be introduced with a meaning of the distance at which the photocurrent reduces by a factor of e due to recombination. Variation of the filling factor of SC IVC due to the presence of contact grid is then analytically expressed via this length. It is found that in unoptimized case, when the distance between contact strips l is much longer than L, the photocurrent collection is determined by lesser, as compared to L, distance, at which the front layer potential changes from the value of Vm under contacts to the open- circuit voltage between the contacts. In this case the change of IVC filling factor due to the presence of contact grid is expressed again analytically via this new characteristic length. In the intermediate case, when l ≈ L, the solution of the problem can be found by numerical methods only.