Cadmium sulfide thin films manufactured by chemical bath deposition method

Abstract

The objective of this work was the investigation of CdS grown by CBD on commercial glass and glass covered by transparent conductive oxide (TCO) substrates. Both TCO and CdS are window layers influencing the photovoltaic response of the cell. CBD technology offers the possibility of the deposition of a thin uniform film with a minimal thickness on a rough substrate surface. CBD growth of CdS using uncoated glass substrates enabled optimization of deposition parameters, e.g. concentrations of CdSO/sub 4/, NH/sub 3/ and thiourea SC(NH/sub 2/), bath temperature and deposition time. Successively glass plates coated with TCO (SnO/sub 2/, ZnO) layers were used as substrates. Both as-grown and air-annealed samples were studied. Investigation of optical transmission in the range 350 - 2200 nm, using Perkin - Elmer Lambda 19 spectrophotometer enabled the evaluation of heat treatment and selected technological parameters on CdS and CdS/ TCO bilayer optical properties. SEM and AFM surface morphology investigations indicate that CdS films reproduce morphology and roughness of the polycrystalline TCO sublayer. That conformal growth and thickness uniformity of cadmium sulfide thin films deposited by CBD technique are presumably the main reasons of their superior quality as buffer layers in CIS solar cells.