Chemical Bath Deposition and characterization of CdS – PbS thin films.

CdS–PbS thin films have been deposited on glass substrates by the chemical bath deposition technique. Cadmium sulphide thin layer was first deposited on glass substrate from a solution of cadmium chloride (CdCl2) and thiourea (NH2CSNH2) with triethanolamine (TEA) as complexing agent. CdS – PbS films were obtained by depositing lead sulphide (PbS) films on the CdS – coated glass substrates from a solution of lead nitrate [Pb(NO3)2] and thioacetamide NH3CSNH2. Complexing agent again was TEA while in both cases aqueous ammonia (NH3) created the necessary alkaline medium for the reaction to take place. The energy dispersive X – ray fluorescence (EDXRF) analysis confirmed the composition of the CdS and PbS thin films. Optical measurements were performed with a single-beam UNICAM Heλ 105 Spectrophotometer in the wavelength range of 195nm – 1000nm. The optical transmittance of CdS-PbS films is extremely low, in most cases zero within the UV and first half of the visible region but peaked at 49.4% (at λ = 994nm) for the 150oC air-annealed samples and at 44.7% (at λ = 994nm) for the as grown samples in the near infra-red region. The absorbance is infinitely large in the UV and first half of the visible regions for both as-deposited films and annealed films, respectively but falls exponentially between the second half of the visible and near infra-red regions. The films have peak reflectance within the visible region. The films showed good characteristics for deployment not only as UV filters but also in solar control coating applications.Keywords: Chemical bath, CdS, PbS, Thin Films, transmittance