Study On Performance Improvement Of Polymer Solar Cells Using Interface Modifications

According to the US Energy Information Administration,the global energy consumption will increase by 28%by 2040,among which China and India will lead the global energy consumption growth.The development and utilization of new energy is of great urgent.Compared with traditional inorganic solar cells,polymer solar cells have promising applications due to their low cost,compatibility with flexible processes,and the ability to be produced on a large scale and at low cost through printing and coating technologies.They have become a new option for renewable energy that can be commercialized.At present,the maximum efficiency of a single polymer solar cell has exceeded 18%,showing a very good efficiency improvement trend and development potential.However,there is still a big gap between the efficiency and the most commonly used silicon solar cell in business.Therefore,improving the efficiency of polymer solar cells is of great significance for their commercialization.At present,the device efficiency can be improved by the development of new active layer materials,material performance of ascension in the physical properties（mainly including light absorption enhancement and the increase in the carrier mobility）and chemical properties（including the use of the ideal solubility and solution viscosity that can improve the quality of film forming of the active layer）.Interface modification and device structure optimization can further improve the performance of polymer solar cells.Therefore,the in-depth study of various interface materials in polymer solar cells and their influence on interface characteristics,and the design of innovative device structures will help to raise the upper limit of photoelectric conversion efficiency and promote the commercial application of polymer solar cells.In this paper,aiming at improving the photoelectric conversion efficiency of polymer solar cells,high performance polymer solar cells were designed and fabricated through the optimization of cathode interface modification materials,anode interface modification materials and device structure design.The results in this thesis are summarized as follows.（1）Improving the performance of polymer solar cells by cathode interface modification.Electron extraction in inverted polymer solar cells was optimized by introducing a PFN/PFBT composite intermediate layer as an electron transfer layer.Hydrophobic PFBT was deposited on ITO electrode,and the inherent interface defects of ITO cathode were alleviated by surface topography modification,and the interface area between cathode and active layer was increased so as to improve the interfacial contact of the film.This interface strategy can effectively improve the efficiency of electronic extraction,and the energy conversion efficiency of the device is increased from 8.02%to 9.74%.The developed PFN/PFBT composite layer can provide an effective solution for material selection and device fabrication of low-cost polymeric solar cell devices.（2）Improving the performance of polymer solar cells by anodic interface modification.A PEDOT:PSS/IPA electrolyte intermediate layer was added between the active layer and Mo O₃ in polymer solar cells to optimize the morphology transition of PTB7:PC₇₁BM phase to improve the anodic interface contact.By adjusting the boundary morphology and energy level arrangement,the composite hole transport layer can passivate the interface trap,reduce the defect state and promote the charge carrier transport.Using this mechanism,the open-circuit voltage,short-circuit current and filling factor of the device are improved at the same time,and the device achieves a high energy conversion efficiency of 9.60%.Furthermore,the anode buffer layer polymer solar cell structure was designed to improve the device efficiency through directional microstructure evolution.The spectral absorption of polymeric solar cells and the efficient capture of photogenerated excitons are improved by using uniformly dispersed island Cu Pc particle accumulation,which acts not only as a light field spacer but also as multiple energy donors.The energy conversion efficiency of the modified solar cell with Cu Pc sandwich reached 9.726%,and the filling factor and short-circuit current in the device were enhanced simultaneously.In addition to enhanced light absorption and conversion,the tailor-made anode energy level cascade and optimized boundary morphology promote efficient charge dissociation and transport,which effectively inhibits bimolecular recombination at the interface.These interface engineering strategies provide a simple way to improve the charge transport in the device,and also open a new way to modify the interface anode of inverted polymer solar cells.（3）High efficiency semi-transparent polymer solar cells with high transmittance and adjustable color were realized through the design of composite electrode structures.An Ag/Mg F₂/Ag microcavity electrode with high transmittance and adjustable color was designed and fabricated,and the new electrode was successfully applied to the design of colorful polymer solar cell.The peak transmittance of blue,green and red polymer solar cells based on the composite electrode were 35.5%,33.7%and 21.9%,respectively,and the energy conversion efficiencies of the corresponding devices were 13.15%,13.03%and 12.83%,respectively.The composite electrode structure can effectively adjust the color of the device and maintain high efficiency while obtaining high transmittance.This electrode demonstrates the potential of application in highly efficient colorful polymer solar cells and is also expected to be a strong candidate electrode material for future integrated architectural photovoltaic applications.