Investigation On Photoelectric Properties Of TiO₂ Nano-structure Film Loaded With Quantum Dots

In recent years, the quantum dots(QDs)–based composite structures have shown excellent photoelectric performance in fields of photoelectric devices and photocatalytic. In this paper, the traditional n-type semiconductor Ti O2 with good conductivity and stability was hybridized with Pb S QDs. We focused on the electronic transition process of the composite structure as well as the influence of QDs layer on conductive behavior and charge transport process of hybrid film. The major findings in the research are as follow:(1) The Pb S QDs with oleic acid(OA) capped were synthesized by hot- injection method under various reaction time. The luminescence spectra showed the size-related red shift by increasing reaction time. The effect of 3- mercaptopropionic acid(MPA) modification on optical properties of Pb S films and on the photoelectric properties of the devices with structure of FTO/Ti O2/Pb S/Au were concerned. The discussion indicates that the replacement of short ligands by MPA can change surface states of Pb S QDs prepared by long ligands OA and reduce interspace between Pb S QDs. It improved the carrier transport ability in Pb S QDs film and enhanced the photoelectric conversion efficiency of the device from 0.32% to 0.48%.(2) The all- inorganic solid bulk-heterojunction photoelectric device based on the Pb S QDs embedded in Ti O2 nanocrystalline film was simply fabricated by SILAR method. The influence mechanism of heat-treatment temperature and growth layers of Pb S Q Ds film was discussed. The experimental condition was optimized for better device behavior. We also fabricated the Pb S(Cd S) film via alternate deposition of Pb S and Cd S to modify the Pb S surface. After Cd S modificatied, the open-circuit voltage, short-circuit current density, incident photon to current conversion efficiency(IPC E) and the carrier recombination resistance for the decvice were increased of 200%, 35%, 50% and 150%, respectively. The dark J-V curves indicated a thousand-fold decrease of the trap state density. These results suggested that the strategy of alternate deposition of Pb S and Cd S was benefited for the depression of charge carrier recombination.(3) The photoelectrochemical(PEC) performance and photocatalytic activity of Ti O 2 nanorod arrays(NRs) loaded with carbon quantum dots(CQDs) have been investigated. In comparison with Ti O2 NRs, the absorption ability of Ti O2 NRs loaded with CQDs was enhanced. The transient photocurrent and open-circuit potential under visible light illumination were increased of 300% and 2.5%, respectively. The photocatalytic degradation efficiency of Methylene Blue(MB) under visible light illumination was increased from 25% to 33%. The electrochemical impedance spectra(EIS) and Mott-Schottky plots were measured to investigate the charge transport. With CQDs loaded, the charge transfer resistance and the electron lifetime were improved. The negative shift in flat-band potential and the position raise in conduction band both enhance the electron reduction properties.