Preparation of NiO/TiO2 Composite Films for Enhanced Dye Sensitized Solar Cell Efficiency

Abstract

Abstract Spray pyrolysis technique has been applied for preparing many kinds of thin films because this technique offers a lot of advantages, such as inexpensive cost, uncomplicated process and large scale production. Therefore, the spray pyrolysis technique is used for making pure TiO2 and NiO/TiO2 composite films in this report. A NiO/TiO2 composite film is getting attention to be used as a compact layer in dye sensitized solar cell (DSSC) because NiO can be used as a hole collector and a barrier for energy recombination properties. Moreover, the NiO/TiO2 composite film exhibits superhydrophilic properties that can increase absorption efficiency for a dye solution. This study has an objective to improve the efficiency of DSSC by changing the ratio of NiO/TiO2 in the composite films. The pure TiO2 and NiO/TiO2 composite films were prepared at 200℃ by spray pyrolysis technique using a Ti(OCH(CH3)2)4 solution and a mixture of Ti(OCH(CH3)2)4 solution with Ni(NO3)2•6H2O powder, respectively. The effect of the ratio between Ni(NO3)2•6H2O powder and Ti(OCH(CH3)2)4 solution (0.5 atm%, 1 atm%, 2 atm%, and 4 atm% of Ni(NO3)2•6H2O) on the efficiency of DSSCs were studied. The surface morphology, crystal structure and optical properties of TiO2 and NiO/TiO2 composite films on FTO and glass substrates were characterized by using field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and UV-VIS spectrophotometer, respectively. The FE – SEM images showed that the films were smooth surface and dense when prepared at 200 ℃. The XRD results of TiO2 and NiO/TiO2 composite films on the FTO substrates showed that the TiO2 crystals were anatase phase because the peak at 25.30 corresponds to (101) planes of anatase. The spectrophotometer results showed that the optical transmittance for all samples were about 80%. For the energy conversion efficiency characterization, it was found that the NiO/TiO2 composite films that were prepared from 0.5 atm% of Ni(NO3)2•6H2O solution had the better energy conversion efficiency than TiO2 films.