Research On Photoelectric Performance Based On CdSe/CdS Co-sensitized Quantum-dot-sensitized Solar Cell

With the rapid consumption of fossil fuels on earth, and the increasing environmental pollution problems.New type of clean, renewable energy has become the world universal attention and research.The solar energy as a kind of an inexhaustible, inexhaustible green energy, and the use of solar energy is one of the main ways to make low cost, high conversion efficiency, abundant raw materials and pollution-free photovoltaic cells.Over the past several years, quantum-dot-sensitized solar cells?QDSSCs? have gained much attention as an alternative to organic-dye- sensitized solar cells due to their versatile properties of high molar extinction coefficient, multiple exciton's generation, tunability of the bandgap and the theoretical photovoltaic conversion efficiency?PCE? of 44% boosted up to the Shockley-Queisser limit of 32% for semiconductor solar cell. Nevertheless, compared to dye-sensitized solar cells?DSSCs? and perovskite solar cells, QDSSCs still show rather limited efficiency. To achieve the higher efficiency, the crucial factors are the improvement of light harvesting efficiency, the reduction of charge recombination and the faster transfer excited electrons.In the thesis, basing on Cd S/Cd Se co-sensitized system, focusing on how to optimize the deposition of ODs and the charge transfer path in QDSSCs to improve the efficiency of QDSSCs were designed. It mainly includes the following three aspects:1)The modification of Ti O₂ photoanodes, Ti O₂ hierarchical spheres?Ti O₂-HS?have been fabricated by a simple hydrothermal method in this paper. These Ti O₂-HS composed of the aggregations of Ti O₂ nanowires with countless porous holes show good electronic transfer, high loading of quantum dots and high diffused re?ection ability. These Ti O₂-HS were designed as the overlayer for light blocking and applied to Cd Se/Cd S co-sensitized solar cells?QDSSCs? based on bare Ti O₂ nanoparticles?Ti O₂-NP?. The results show that the values of the short-circuit current density?Jsc?and the power conversion efficiency??? have been increased up to 16.81 m A·cm-2 and4.50%. which has increased by 24.7% compared to the QDSCs without a scatteringlayer?3.61%?.2) basing on Cd S/Cd Se co-sensitized, Pb S, Cd S and Cd Se quantum dots?QDs?were assembled onto Ti O₂ photoanodes by simple successive ionic layer absorption and reaction?SILAR? to fabricate Cd Se/Cd S/Pb S co-sensitized solar cells. An improved power conversion efficiency?PCE? of 5.11% was achieved for Cd Se/Cd S/Pb S co-sensitized solar cells at one sun illumination, which had an improvement of 22.6% over that of the Cd Se/Cd S co-sensitized solar cells?4.17%?.This enhancement is mainly attributed to their better ability of the absorption of solar light with the existence of Pb S QDs, the reduction of charge recombination of the excited electron and longer lifetime of electrons.3)Using the CBD method, Mg²⁺ doped Cd Se with different percent and Cd S quantum dots co-sensitized solar cell were prepared. With doping Mg²⁺cation in Cd Se, the conduction band and valence band of quantum dot improves, which is benefical to charge transport in solar cell, reducing the recombination between electrons and holes, improving ability of the absorption of solar light. Therefore, the photocurrent and power conversion efficiency are improved. The results show that the values of the short-circuit current density and the power conversion efficiency???have been increased up to 21.15 m A·cm-2and 5.89%.