| The solar power as a clean and pollution-free energy has become the ideal way to solve the crisis of energy and the environment in today’s society.Over the past decades,the quantum dot solar cells with low cost,easy preparation and quantum size effect and multiple exciton effect of used QDs sensitizers became a promising candidate for the third generation solar cell technology.At present,the theoretical limit efficiency of QDSSCs has reached 44%,but the highest photoelectric conversion efficiency is only 12.23%in the actual research.There are several reasons which is responsible for the moderate performance of QDSSCs,such as lower loading levels,uncontrollable size,poor crystalline and uneven distribution of the QDs deposited on the photo-anodes by the traditional deposition method.Besides,long chain organic ligands in the surface of colloidal quantum dots can create insulating barriers that blocks charge transport and injection from QDs,etc.According to the above reasons,The major research work of this thesis as follows:(1)First,oleylamine and oleic acid capped CdS QDs with a homogeneous distribution of size and high crystallinity were synthesized.Second,CdS QDs were attached to the surface of TiO2 by the ex-situ linker-assisted approach and sensitized photo-anodes were treated with CdSe and ZnS.Finally,sensitized photoanodes,PbSe and the polysulfide electrolyte assembled into the QDSSCs with the sandwich structure.The properties of CdS QDs before and after exchange with MPA characterized by XRD,TEM,UV-Vis,IR and EDX.The photovoltaic performance of the cells fabricated by the different thickness photo-anodes and the different cycles of CdSe were recorded by J-V,EIS,OCVD,M-S and EDX spectrum.As a result,the optimized film thickness is about 20μm,CdSe deposition cycles is seven and PCE is 3.74%.These results suggested that the linker-assisted approach can efficient,homogeneous deposited QDs on the surface of TiO2 and the thickness of the photo-anode films is one of the key factor determined the performance of sensitized solar cells.It can regulate numbers of photo-generated electrons and light harvesting efficiency via the controlling sensitizer loading level.(2)Sn2S64-ligands were synthesized in the solvent of hydrazine.Then,CdS QDs were deposited on TiO2 photo-anodes by in situ linker-assisted assembly method with Sn2S64-ligands.The sensitized photo-anodes were fabricated into the cells.We study the influence of the different CdS deposition cycles on the performance of the cells.Finally,the best cycles for 2 times and the corresponding cell efficiency is 0.87%.We also found the reasons of lower efficiency of the cells has the following two points:① lower sensitizer loading levels in the photo-anodes;② the deposition method used by us can’t completely replaced the original organic ligands,so that organic residue hindered the transfer of the interface.Therefore,the application of these inorganic ligands still needs further improvement. |
