Electrical and microstructural properties of screenprinted CdS layers for CdS-CdTe solar cells

Results are presented on an investigation into the development of electrical and microstructural properties of sintered CdS films as a function of sintering parameters, and the double role of the evaporating flux is illustrated. CdCl₂ used in the sintering, acting both as a sintering flux and as an n-type dopant. The sintering temperature and sintering period were varied, and special attention was paid to the controlling of the flux evaporation. A study of the microstructural and electrical properties was performed, using SEM-analysis, atomic absorption spectroscopy, resistivity, and Hall measurements. Data are presented on grain size, sheet resistance, carrier concentration, and carrier mobility versus sintering parameters. The results are explained in terms of the double role of the evaporating flux. It is found that the microstructure of screen-printed CdS films, sintered with the aid of CdCl₂ as a flux, is determined by the sintering temperature and by the effective sintering period, which is the period during which the flux can be kept active within the film.