Synthesis, Characterization And Application Of Organic Semiconductor Materials Containing Perylene Diimide (PDIs)

In the field of organic photovoltaics, fullerene and its derivatives are an important class of n-type electron acceptor materials. However, their disadvantages such as narrow wavelength absorption, high affinity, poor solubility, have severely limited their wide application as electronic acceptors for organic solar cells and have largely hampered further improvement of the device performance. However, the non-fullerene n-type organic acceptors usually appear to possess lots of attractive advantages, such as adjustable energy levels, facial synthesis, good solubility, low processing cost. More importantly, when compared to the fullerene and its derivatives, this kind of acceptors has wider absorption that allows absorbing more sunlight to generate electricity. It has been the subject of intensive academic interest over the recent years.Carbon nano-tubes and graphenes, typical representatives of one and two dimensional carbon nano-materials, have a high electrical and thermal conductivity, high carrier mobility and other excellent electrical properties. Thus, both of them have important applications in photoactive layers and transparent electrodes of organic solar cells and so on. However, nowadays, their applications in the filed of solar cells are still in their infancy and the preparation technology is complex and of high cost. Moreover, the graphene thin films and carbon nano-tubes obtained by conventional preparation methods have high defect density. Simply using physical or chemical purification methods can not solve the problem. All of these will reduce electors transporting ability, increase excitons combination and thus can not significantly improve photoelectric conversion efficiency of the cells. Therefore, our work includes the following two aspects.Firstly, in order to open the electronic gap of graphene effectively and to solve the difficulties of preparing, we design and synthesize a new graphene ribbon architecture that consists of perylenediimide(PDI) subunits fused together by ethylene bridges through atomic precise controlled organic synthesis method. We created PDI oligomers consisting of dimmer, trimer, and tetramer. The steric congestion at the fusion point between the PDI units created helical junctions, and longer oligomers form helical ribbons. Thin films of these oligomers form the n-type active layers in organic solar cells and the photoactive conversion efficiency of dimer is 6.05%.Secondly, in order to get mono-diameter and controllable size of carbon nanotubes, we synthesized growth templates of carbon nanotubes through atomic controlled organic synthesis method. These templates belong to cycloparaphenylenes(CPPs) consisting of PDI subunits,they are tiraras and crowns. This is the first time that we have incorporated electron-accepting materials into macrocycles and separated them successfully by High Performance Liquid Chromatograpy(HPLC) and studies their molecular chirality.