Grain structure of CdTe in CSS-deposited CdTe/CdS solar cells

The grain structure of CSS-deposited CdTe/CdS solar cells was studied as a function of annealing time in the presence of CdCl2. The structure was studied by chemically bevelling the cell to reveal the grains at all depths of the layer. The grain boundaries were revealed using a defect sensitive etch, and photomicrographs taken at intervals down the bevel. These photomicrographs were then analysed computationally. Histograms of grain radius for each micrograph were fitted well by the Rayleigh distribution. The average grain radii were found to vary linearly throughout the CdTe layer as (r) over bar = (0.107 x d) + 1.06, where d is the distance from the interface. This behaviour was unaffected by the CdCl2 treatment and is discussed with reference to a kinetic model of grain growth. Finally the use of correlation plots in analysing grain centroid distribution is described and some results presented. (C) 2000 Elsevier Science S.A. All rights reserved.