Application Of Inorganic Semiconductor Nanomaterials In Polymer Solar Cells

Recently, polymer solar cells containing many advantages such as low preparation cost, light weight, solution preparation and flexible production overcome the characteristics of the high cost, poor mechanical properties and other defects from traditional inorganic solar cells, which caused the wide attention. Although the reported photoelectric conversion of organic solar cells based on fullerene derivative and conjugated polymers has been more than 10%, the absorption coefficient of fullerene derivatives or polymers is not optimistic. In bulk heterojunction solar cells, energy level offset and interface contact between active layer and electrodes are important factors. Barrier of a few tens of m V between optical layer and the electrode can cause charge accumulation and composite. So the establishment of effective charge extraction and well ohmic contact not only can enhance the stability of the device, but also is an important strategy to improve the photovoltaic devices.Inorganic semiconductor nanocrystals could solve the interface problems. Firstly, removing excess insulated ligands on the surface of nanoparticles would make higher current. If the nanoparticles produce agglomeration due to ligand exchange under high temperature, phase separation will make poor contact between the interface of active layer and the electrode. Secondly, transmission of free charge and separation of the exciton is affected by interpenetrating continuous network structure, providing efficient continuous passage. Thererefore, improving the dispersion of nanocrystals exchanged ligands and using 3D structural semiconductor nanocrystals modified electrode interface can be a significant solution to these problems.On one hand, the tetragonal Cu2 Zn Sn Se4 nanoparticles were prepared using hot injection method in this thesis as hole transport layer applied in device instead of PEDOT:PSS. Removal of the external ligands improves the ability of charge transmission exchanged by pyridine. After the exchange, it is easy to gather resulting in the leakage of the current. In order to solve the problem of aggregation of nanoparticles, introducing a small amount of graphene oxide(GO) as the nanotemplate to load dispersion semiconductors, not only make the nanocrystals and graphene oxide attracte closely via electrostatic interaction and improve the dispersion, also regulat anode buffer layer work function. It is important to enhence the efficiency of polymer solar cells.On the other hand, this paper also reports the preparation of Cd Se tetrapods(TPs) nanocrystals modified the surface of Zn O buffer layers. The formation of 3D network structural electron transmission and extraction channel increases the short circuit current and reduces the surface defects of Zn O. The series resistance of the entire devices is reduced, resulting in improvement of the fill factor greatly. In addition, by changing the concentration of Cd Se TPs, the optimum proportion makes the short circuit current increase from 7.39 m A·cm-2 to 8.03 m A·cm-2, the fill factor improve from 52.9% to 61.3%.