Theory of grain-boundary and intragrain recombination currents in polysilicon p-n-junction solar cells

The physics controlling recombination in polysilicon p-n-junction solar cells is described. Analytic models characterizing this recombination, whose parameters can be related directly to experiment, are developed. The analysis reveals that, in general, the description of intragrain and grain-boundary recombination in a polysilicon solar cell requires the solution of a nonlinear three-dimensional boundary-value problem. Cases of practical interest for which this problem is tractable are discussed. The analysis predicts an
\exp (qV/2kT)
dependence (the reciprocal slope factor is exactly two) for carrier recombination at a grain boundary within the junction space-charge region of a nonilluminated, forward-biased cell. This result, and others of the analysis, are consistent with preliminary experimental data.