Study Of Quantum Dots Deposition On The Surface Of TiO₂ And Their Applications For Quantum Dots Sensitized Solar Cells

With the characteristics of band gap controllable, high extinction coefficient and the multiple exciton effect, quantum dots made the quantum-dots sensitized solar cells become the focus of the third generation solar cells. However, Cd S/Cd Se quantum dots sensitized solar cells still exhibit moderate power conversion efficiency, limited by low quantum dots coverage and serious charge recombination. Herein, we have studied the quantum dots deposition method to improve the energy conversion efficiency. The main results achieved in this work are listed as following:1. We have developed a novel route to increase the coverage of the quantum dots. 1-dodecanethiol are used as a surface protection molecules to absorb on the surface of the quantum-dots. Then, in the secondary chemical bath process, the new emerged quantum-dots would only grow on the Ti O₂ surface and thus the coverage would remarkably increase. Eventually the coverage of quantum dots got up to 85.4%. This effectively enhanced light utilization and led to an increase in the photocurrent of the QDSSCs. And the reduced blank surface of Ti O₂ suppressed the recombination of electron-hole efficiently.2. We designed a new quantum dots deposition method, that Cd Cl₂ dispersed spontaneously on to the surface of Ti O₂, and converting the Cd Cl₂ in situ to Cd S by chemical vapor deposition. This method can make quantum dots form uniform dispersion while preventing their aggregation, thus suppressed the internal recombination of quantum dots and interface recombination between Ti O₂ and electrolyte.3. The applicability of the spontaneous dispersion method was studied by comparing two kinds of photoanode with different specific surface area and pore diameter distribution, anatase Ti O₂ nanosheets-based hierarchical spheres and Ti O₂ hierarchical hollow spheres. We found that this method was more suitable for photoanode with large pore distribution. As a result, the conversion effifiency of 6.10% based on Ti O₂ hierarchical hollow spheres photoanode was obtained.