Preparation And Photo-electric Properties Of TiO₂ /Narrow Bandgap Semiconductor Composite Films

TiO₂ was applied widely in the water splitting, sensors, photocatalysis and dye sensitized solar cells(DSSC), especially DSSC for its conversion photo energy to electric energy directly. In the study people discover that: 1. The surface/interface states in anode have important fact to the carrier transfer. 2. The sensitivity to light, absorbance range and cost of organic dye limit its application. Researchers found that one dimention array structure as nanowires and nanorods can help to improve charge transfer notably, and narrow bandgap semiconductors were used as sensitizer responding to their large absorbance coefficient, low cost et al. To improve this condition, we prepared TiO₂ nanorod array, TiO₂/CdS quantum dot and TiO₂/CuInSe₂ composite film. The work is mainly in following three aspects:We prepared TiO₂ nanorod array on FTO with/ without seedlayer, glass with/ without seedlayer, respectively. The morphologic, structure and photoelectronic properties were investigated with SEM, XRD, SPS, U-V absorbance, respectively. The results showed that the substrate had important impact on the TiO₂ not only on the improvement to the morphology, but also to the interface states. It is mainly resulted from the lattice match between TiO₂ and SnO₂.Based on the TiO₂ array, we prepared CdS quantum dots/ TiO₂ composite film and investigated its elemental composition, structure and phtotoelectronic properties with SEM, EDS, TEM, U-V reflectance spectrum and surface photovoltage techniques. These results showed that 90 nm thicknesses of CdS quantum dots reached the deepest incident length. The accumulate of electrons in CdS layer surface state accelerated the injection of electrons from CdS to TiO₂ on one fact, and on another fact the electrons in the inner layer form a barrier blocking the ones in the outer layer, which is the major reason of carrier lose.Based on the TiO₂ nanorod array, we tried to prepared Cu/In/Se compound/ TiO₂ composite film with electrodeposition method. These experiments were the previous work of preparation of CIS/TiO₂ composite film. During the process of deposition we found the hydrogen evolution reaction near the cathode prevented the ions deposition to the interspace of nonarods, which result in the low quality of Cu/In/Se compound film and low separate efficiency of carriers.