Research Of Solution Processed Ito-free Organic Solar Cells

Solar cells have very promising applications in the fields of energy supply and mobile electronics integration. Organic solar cells have a lot of advantages, such as light weight, mechanical flexibility and wide range of material sources, which can be well integrated with mobile electronic products and provide sustainable energy supply.Traditional organic solar cells use indium tin oxide (ITO) as the transparent electrode, which, however, has disadvantages in complicated processes and poor mechanical flexibility. This thesis developed an all solution processed transparent electrode combining the high conductive PEDOT:PSS (PH500) with inkjet-printed Ag grids in a sandwich structure of PEDOT:PSS/Ag grid/PEDOT:PSS. By optimizing the drop spacing and the surface energy of bottom PEDOT:PSS layer, silver lines with 40 nm height and 80μm width were formed by inkjet printing. With the formed silver grids, a sheet resistance of 35Ω/□and transmittance of 80% were achieved for the fabricated PEDOT:PSS/Ag grid/PEDOT:PSS conductive films. Moreover, the sheet resistance and transmittance of PEDOT:PSS/Ag grid/PEDOT:PSS can also be optimized by changing the separated distance of silver grids.Before using the developed electrodes for fabricating organic solar cell devices, process optimization for forming the active layer were conducted based on the structure of ITO/PEDOT:PSS/P3HT:PCBM/Al. By comparing the performance of devices fabricated under different conditions of pre-annealing, post-annealing, annealing temperature and annealing time, an annealing process by combining pre-annealing and post-annealing was found to be able to obtain the best device performance with the power conversion efficiency of 2.1%.Finally, by using the developed PEDOT:PSS/Ag grid/PEDOT:PSS transparent conductive electrode to replace ITO as the anode, organic solar cells with the PCE of 1.73% were achieved. It was shown that the device performance varied with different silver grid separation distances, and the best performance was obtained when the silver grid separation distance is 1 mm.