Research On Air-brush Spray Deposition Used In Fabrication Of Organic Solar Cells

This dissertation prensents a systematically analysis and studies on the Air-brush spray deposition which was used in fabrication of organic solar cells. A model of the air-brush spray process was founded and it could be divided into three sub-processes, spray, fly and deposition. The fine atomized droplets size could be limited by the ratio between surface tension and density of the solusion. The droplets are volatilized and concentrated on its way to the substrate, and volatility of the solvent is major factor which decide the rate of size reduction. When drotlets arrive to substrate, they will spread out and dried to spots. These spots were not smooth but like a basin, high on the edge and low in the center. The film fabricated by air-brush spray deposition is formed by a lot of spots, and the micro appearance of the film is strongly related to the feature of spots.The relationships among preparing condition, micro appearance of films and performance of polymer solar cells which fabricated by air-brush spray deposition in practical cases were studied. The relationship between preparing condition and micro appearance of films can be described like that:solvent with low surface tension, high density and weak volatile will lead to more smooth films; high concentration of the solution and temperature of the substrate will lead to rough film. Other conditions, such as carrier gas pressure, feed rate of the solution and ambient temperature, have weak impact on film appearance. And the relationship between micro appearance of films and performance of polymer solar cells can be summarized to the roughness of the films. The roughness has strong impact on the performace of polymer solar cells, and rough film surface profile lead to poor fill factor, but it also enhance the current density of the devices.Many devices with different structures (such as air-brushed buffer layer device, bilayer heterojunction device, bulk heterojunction device, qantum dots enhanced P3HT:PCBM bulk-heterojunction device and large area device) were fabricated and described. The conversion efficiency of air-brushed devices could be rivaled to spin-coated devices in small size, and conversion efficiency of the device with60mm*60mm active area can reach to1%.All the result demonstrated that air-brush spray deposition was a good method which can easily produce both small and large area polymer solar cells devices with low cost. And it also will be a very important development direction of the research on fabrication of polymer solar cells in the future.