Structure Regulation And Performance Optimization Of Quantum Dot Sensitized-Solar Cell

The direct conversion of solar energy into electrical energy has great significance to solve the problem of energy crisis and environmental issues.Quantum dot sensitized solar cell, as the third generation solar cell, has received widespread attention in the photovoltaic industry due to the high theoretical energy conversion efficiency and low production cost. Unfortunately, to date, the photoelectric conversion efficiency of quantum dot sensitized solar cell is still lower than those of traditional solar cells.Based on the structure and the principle, this article investigated the preparation method of quantum dot sensitized photoanode, the energy level regulation of quantum dot, the material properties of photoanode and counter electrode, and the preparation process of the device on the performance of quantum dot sensitized solar cell. We designed the CdPbS quantum dot sensitized electrode prepared by the codeposition method, the tunable energy band CdSexS(1-X) quantum dot sensitized photoanode, the nitrogen doped microporous titania spheres for photoanode, and the inorganic organic nanocomposite TiO2-PEDOT for the counter electrode. Moreover, we investigated the influence of these operations on quantum dot-sensitized solar cell.Firstly, we fabricated CdPbS quantum dots sensitized electrode by the codepositon method. Through the investigation of the Pd/Cd ratio, the electrolyte composition, the sedimentary sensitization cycles, and the thickness of TiO2 nanocrystalline film on the performance of quantum dot sensitized solar cell, the optimization of preparation method was determined. The results indicated that the CdPbS quantum dots sensitized solar cell prepared by the codepositon method shows better performance than the single PbS, CdS sensitized and PbS/CdS co-sensitized solar cells, which is attributed to the improvement of light absorption by the control of the Pd/Cd ratio.Secondly, tunable energy band CdSexS(1-X) quantum dot (QD) was developed for QD-sensitized solar cells(QDSSCs) by the successive ionic layer adsorption and reaction (SILAR) technique. The results indicated that the energy band and the light absorption of CdSexS(1-x) QD could be controlled by the ratio of the sulphur (S) and the selenium (Se). Compared with the conventional CdS/CdSe system, its absorption spectrum and monochromatic incident photon-to-electron conversion efficiency (IPCE) spectrum show higher light harvest ability and broader response wavelength region. As a result, a high energy conversion efficiency of 2.27%was obtained with the CdSexS(1-x) QDSSCs under AM 1.5 illumination of 100mW-cm-2. After being further treated with CdSe QDs, the CdSexS(1-x/CdSe QDSSC yielded an energy conversion efficiency of 3.17%due to the enhanced absorption and the reduced recombination. It can be expected that the tunable energy band QD controlled by the ratio of atoms can contribute to the higher efficiency QDSSCs.Thirdly, the photovoltaic performance of quantum dot-sensitized solar cell (QDSSC) based on mesoscopic nitrogen-doped TiO2 spheres prepared by solvothermal method was investigated. The results indicate that CdSexS(1-x)/CdSe QDSSC based on this mesoscopic nitrogen-doped TiO2 spheres shows an energy conversion efficiency of 3.67%, which is higher than that of the undoped TiO2 spheres (2.14%). The electrochemical impedance spectroscopy shows retards charge recombination is occurred on nitrogen-doped TiO2 spheres photoanode. The improvement of the photovoltaic performance of QDSSC could be attributed to the retarding charge recombination, the acceleration of the transfer rate of electrons, higher quantum dots loading and enhanced light scattering in the N-doped TiO2 spheres film. A higher photovoltaic performance could be expected for other QDSSC with this N-doped TiO2 sphere material.Finally, the TiO2-poly(3,4-ethylenedioxythiophene) inorganic-organic composite material was prepared as counter electrode material for CdS quantum dot sensitized solar cell. The results indicated that its energy conversion efficiency(1.56%) is higher than those of the Pt(0.87%) and pure poly(3,4-ethylenedioxythiophene)(1.35%) electrodes based solar cell. Moreover, the composite material is not easy to fall off due to the good adhesion between TiO2 nanocrystalline film and the conductive substrate. Due to the polymerization of a more uniform, aperture suitable poly(3,4-ethylenedioxythiophene), the charge transfer resistance is decreased and the catalytic performance is improved with the higher surface area. As a result, it could be expected that this material is suitable for the counter electrode materials of the quantum dot sensitized solar cell.