An-Najah Staff

Nano-sized CdS films were prepared by different techniques, namely electrochemical (ECD), chemical bath deposition (CBD) and electrochemical followed by chemical bath deposition (ECD/CBD). The deposited films were modified by annealing at 250°C and 350°C. Cooling of pre-heated films to room temperature was performed by slow gradual process and by quenching. Moreover, electro-active matrix of tetra(-4-pyridyl) porphyrinatomanganese (ΙΙΙ) sulfate complex (MP) and commercial polysiloxane paste (Sil) was used to coat the prepared CdS films. The effects of MP concentration and thickness of MP-Sil matrix, on CdS film electrode characteristics, were studied. Effect of annealing the coated CdS films at 120°C on its characteristics was also studied. Atomic force microscopy (AFM) images, X-ray diffraction (XRD), photoluminescence (PL) spectra and electronic absorption spectra were used to characterize the prepared electrodes. Photo-electrochemical (PEC) characteristics of different film electrodes, such as photo J-V plots, dark J-V plots, conversion efficiency and stability were all investigated. In general, XRD results showed that annealing process didn’t affect the film grain size of CdS nano-particles. AFM images showed that the annealed films have more uniform, smooth and more homogeneous surfaces than non-annealed counterparts. PL spectra of annealed and non-annealed films were not much different except in emission intensity values. Annealing enhanced the PEC characteristics by increasing the conversion efficiency and stability. AFM images showed that the slow cooling process gave more uniform, smooth and homogeneous film surfaces than fast cooling process. PL spectra of both films were not much different except in emission intensity values. Moreover, the slow cooling process gave higher conversion efficiency value than quenching process. The stability was the same for both films. The effect of coating CdS films with MP-Sil matrix was studied. PL spectra of coated and uncoated films were not much different except in emission intensity values. Moreover, the uncoated CdS films showed higher conversion efficiency than the coated films at the beginning of the measurement. After some time, the efficiency and stability of the coated electrodes were better than that for the uncoated ones. The effect of MP concentration inside the coating film was also studied. The PL spectra for three films were not much different. The highest conversion efficiency was obtained with CdS films having medium concentration of MP. Film stability was not influenced by changing MP concentration. The effect of thickness of MP-Sil matrix was studied. PL spectra for three films were not much different, except in emission intensity values. The highest conversion efficiency was obtained for CdS film with the thinner MP-Sil matrices. However, the electrode stability was not influenced by changing of MP-Sil matrix thickness. Effect of annealing of coated CdS films was also studied. PL spectra was not affected by annealing except in emission intensity value. Annealing the coated CdS films increased the PEC conversion efficiency but the stability was not influenced.