A Simple Method to Extract the Diffusion Length from the Output Parameters of Solar Cells - Application to Polycrystalline Silicon

摘要

This work presents a simple method to obtain the effective diffusion length L_(eff) a solar cell directly from measured values of open circuit voltage, short circuit current density, and the doping density in the base of the cell. In the second part of this paper, we extract L_(eff) from literature data of polycrystalline silicon cells, with grain sizes from 10~(-2) to 10~4 μm, modeling the extracted L_(eff) as a function of the grain size g, and the recombination velocity S_(GB) at the grain boundaries. For g > 1 μm, our model predicts 10~5 < S_(GB) < 10~7 cm/s. Cells with g < 1 μm, are understood with 10~1 < S_(GB) < 10~3 cm/s. This finding supports the hypothesis that the key to high efficiencies at small grain sizes is the use of {220}-textured films.