Functionalized Nano-ZnO Applied As The Cathode Buffer Layer In Polymer Solar Cells

Organic photovoltaic devices(OPVs) based on conjugated polymer materials have been paid a tremendous amount of attention, partly because they feature many advantageous properties, including light weight, mechanical flexibility, low-temperature and low-cost fabrication of large-area devices. However, the current efficiency of polymer solar cells is still at low. Recently, the main route to improve the efficiency of polymer solar cells is to design a synthesis of new active materials, to regulate the morphology of the active layer and to optimize the interface contact between the active layer and the electrodes and so on. And the optimization of interface between the electrode and the active layer plays very important role. Good interfacial layer material not only improves the contact between the inorganic metal electrodes and organic active layer to reduce the interfacial barrier, but also able to adjust the level of the contact interface, improve the selectivity charge, thus enhanceing charge transport and collection, and ultimately increase the device efficiency. At the same time, the interface layer can effectively avoid the erosion of water and oxygen, and then to improve the stability of the device to a certain extent.In this paper, we mainly made the research about the functionalized nano-Zn O applied as the cathode buffer layer in polymer solar cells. In the first chapter of this thesis, we prepared zinc oxide nanoarrays(ZnO NAs) by hydrothermal methodand, characterizated and tested the corresponding performance. In order to optimize surface property of ZnO NAs, reduce surface defects, finally improve polymer solar cells performance, we used cadmium sulfide(CdS) nanocrystals prepared through successive ion layer adsorption and reaction(SILAR) technique as the surface modifier to functionalize ZnO NAs. The introduction of nano-CdS-films improved the short-circuit current density(Jsc), the open-circuit voltage(Voc), the fill factor(FF) and the power conversion efficiency(PCE) of a polymer solar cell significantly. And this conclusion was also applied in hybrid solar cells still. And in order to simplify the test process,a novel zinc oxide nanoparticles(ZnO NPs) modified by silanization using triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane(TTFO), referred as ZnOF NPs, have been successfully synthesized, and incorporated it into the active layer. Driven by the surface segregation behavior of the fluoroalkyl chains ascribed to their low surface energy, ZnOF NPs can migrate from the blend system with poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester(P3HT:PCBM) to the surface of active layer during annealing process and consequently self-assemble as a cathode buffer layer. Ultimately improve the contact between the organic active layer and the electrode and simplifies the fabrication procedure and reduces.In summary, to design a good interface layer material can not only improve the efficiency of the device, simplify the device fabrication process, but also reduce cost, which is a great benefit for the large-scale commercial production. And combined the organic polymer with inorganic nanocrystals advantages, design a new interface material will make a significant contribution for the development of solar cell.