TX-100 assisted CBD-Cds thin films

Abstract

Among various deposition methods of CdS thin films, chemical bath deposition (CBD) stands out owing to its simplicity and low-cost of fabrication to produce high quality thin films. Triton X 100 (TX-100) is a nonionic surfactant which is widely used as a detergent. In this work CdS thin films were fabricated using the CBD method in the presence of TX-100 (CBD/TX100-CdS). The performances of the fabricated samples were then compared with films deposited without TX-100, using conventional CBD method (CBD-CdS). CBD/TX100- CdS was deposited on thoroughly cleaned fluorine-doped tin oxide (FTO) coated conducting glass substrates using 0.001 M CdSO₄, 0.002 M CS(NH₂)₂, 1.1 ml of NH₄OH solution and 0.647 mg cm⁻³ of TX-100 in a reaction vessel for one hour. For CBD-CdS, same steps were followed with the use of same chemicals except TX-100. Both TX-100 treated and untreated CdS thin films were fabricated under bath temperatures of 40, 60 and 80 ̊C. Later, all the samples were air annealed at 300 ̊C for one hour. The fabricated samples were characterized using GIXRD, SEM, UV-visible spectroscopy, Mott-Schottky and photo electrochemical (PEC) cell. GIXRD results reveal that the deposited films are hexagonal in phase. Transmittance in the range 300-800 nm was found to be higher for CBD/TX100-CdS compared to CBD-CdS samples. The SEM images indicate all the CBD/TX100-CdS has smaller cluster sizes compared to CBD-CdS samples, which leads to higher band gap values obtained from UV-visible spectroscopy for CBD/TX100-CdS. PEC cell measurements yield that both ISC and VOC values for CBD/TX100-CdS are higher compared to CBD-CdS, while CBD/TX100-CdS fabricated at 60 ̊C bath shows the best ISC×VOC product. These impressive ISC values observed for CBD/TX100-CdS samples can be due to higher surface roughness of CBD/TX100-CdS, as a result of its smaller cluster sizes. Additionally, the flat band potential calculations from Mott-Schottky measurements also reveal that the deposited CBD/TX100- CdS films have higher flat band potential compared to CBD-CdS. All these results confirm that the optical and electrical properties of the CdS thin films can be effectively improved by the introduction of TX-100 to the deposition medium.