The Materials And Performances Research On The Active Layer And Buffer Layer Of The Solar Cells

Due to the limitation of non-renewable energy sources such as coal and oil, energyissues have become a bottleneck for international economic development. More andmore countries have begun to exploit solar energy resources to seek alternatives foreconomic development. Among the candidates, green solar energyphotovoltaicsarelikely to occupy an important position in worldwide energyconsumption.Not only are they expected to replace conventional energy sectors, theyare also expected to become the world’s main energy supplier.Compared with traditional silicon solar cells, new generation solar cells such asquantum dot based solar cells and hybrid solar cellshave displayed inferiorperformances. However, their high theoretical power conversion efficiency (PCE)values and easier methods of preparation offer them a broad potential for furtherdevelopment.Also, compared with the long research course of silicon solar cells, theresearch timeof these new generation solar cells is relatively short. To further improvethe performance of the new generation solar cells, we should choose appropriatematerials or design new materials for the different constituent layers, design morereasonable device structures and optimize the interface morphology between each layer.This thesis focuses on solar cells based on different shapes of quantum dots and theorganic solar cells that use two-dimensional transition metal disulfides as the holetransporting layers. We explore the morphology of different quantum dots acting as theactive layer, the morphology of two-dimensional transition metal disulfides acting as thehole transport layers, surface traps and their influences on the devices performance:(1) Narrow bandgap PbS quantum dots and CdSe quantum dots are synthesized bythe hot-injection method.By adjusting the ratio of reactants and controlling the reactiontemperatures, different shapes of quantum dots are prepared.(2)Through suitable surface ligand modification and different ligand treatment methods, these quantum dots are applied on the heterojunction solar cells and hybridsolar cells. Also, we discuss the influence of and possible reason for air oxidation ondevice performances.(3) We use an improved chemical intercalation method to prepare two-dimensionallayered materials including MoS2, NbSe2and WS2. Through characterizations usingUV-visible spectroscopy, transmission electron microscopy, atomic force microscopyand synchrotron radiation X-ray diffraction, we verify the thin-layered structure ofthiscategory of materials, analyse their specific composition after intercalation treatmentas well as the film morphology when applied to devices.(4) The thin-layered materials were used as hole transporting layers in the organicsolar cells and achieved excellent power conversion efficiencies (~8.1%).Through thestudy on the interface between the hole transporting layer and the active layer and thecalculation of the carrier densities of devices with different interlayers, thesesolution-processed thin layered materials are expected to replace the traditional bufferlayer materials, such as thermally evaporated MoO3and conjugated polymer PEDOT:PSS, and be widely used in organic solar cells.