Preparation of Large Grain and Dense CdS Thin Films Using Ultrasonic Agitation Chemical Bath Deposition

Abstract

We deposited CdS thin films onto F-doped SnO2 transparent conductive glass by ultrasonic agitation chemical bath deposition (UCBD). The influence of the annealing and CdCl2-treatment on the surface morphology, crystal structure, and direct band gap of the UCBD-CdS thin films was investigated. The effect of deposition time on the grain size of the CdS aggregates and the stack denseness of the UCBD-CdS thin films was compared. The results reveal that the small grains in the CdS aggregates were melted together and the CdS aggregate size did not change in the UCBD-CdS thin films after the CdCl2-treatment procedure. It is interesting that the ratio of the horizontal to vertical deposition rate varied with deposition time over the deposition period of the UCBD-CdS thin films. The deposition time was very important to obtain large CdS aggregate grains and dense UCBD-CdS thin films. Over a deposition time of 40 min the resulting UCBD-CdS thin films were dense and had a 180 nm grain size of CdS aggregates and a 80.8 nm of thin film thickness. The large-grained and dense UCBD-CdS thin films were suitable for thin film solar cells as a window layer.