Self-cleaning solar cell coatings based on TiO2/ZnO nanocomposite photocatalyst

TiO2 and ZnO nanoparticles are successfully prepared using a sol-gel method. A series of TiO2/ZnO composite films with varying ZnO content were prepared by the drop casting method. The influence of the ZnO content in TiO2/ZnO composite films on the structural, morphological and optical properties was investigated. The XRD measurements indicate that the coating technique to prepare film samples did not affect the structure of the materials for both TiO2 and ZnO films since the diffraction peaks appeared on the pattern in the same peak position as they appear in the standard cards for TiO2 and ZnO powders. FTIR analysis confirmed the successful synthesis of TiO2, ZnO and composite film samples. FESEM microscopy showed that the TiO2 nanoparticles were larger than the ZnO nanoparticles, making the ZnO film appear smoother than the TiO2 film. It indicated the good results of mixing these two nanoparticles because the small particles of ZnO closed the pores of the TiO2 film and the film appeared more smother. The TiO2 film and the 0.75TiO2/0.25ZnO composite film exhibited indirect band gap transition while the ZnO film and the remaining composite samples showed direct band gap transition. The water contact angle was approached to almost zero angle with 15 min of illumination, which is important and necessary for self-cleaning and photocatalytic effects. The I-V characteristic curve of the film coated solar cell was compared with that of the uncoated solar cell. The best efficiency (10.529) was obtained by the solar cell coated with the 0.25TiO2/0.75ZnO composite film.