Design, Synthesis, And Property Study Of Organic Electron-Transporting Materials Based On Derivatives Of Rylene Diimides

Organic electron-transporting materials are the bases for the fabrication of organic semiconductor devices. With investigation of organic optoelectronic devices, such as Organic photovoltaic cells (OPVs), organic field-effect transistors (OFETs) and complementary logic circuits, et al., the developments of organic electron-transporting materials with high mobility, good stability and facile processability are the key factor to restricted the development of organic semiconductors. Rylene diimides such as perylene-3,4,9,10-tetracarboxylic acid bisimides (PBIs) and naphthalene-1,8,4,5-tetracarboxylic diimides (NDIs), are a robust, versatile class of polycyclic aromatic electron-transporting materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities. In this dissertation, we designed and synthesized a series of rylene diimides based on PBIs and triphenodioxazine, and carried on a research on optical properties, electrochemical properties, thermal stabilities and electron-transporting properties.Multifunctional building blocks8and9were efficiently synthesized by fusing a perylene-3,4,9,10-tetracarboxylic acid bisimides (PBIs) core with o-phenylenediamine. In the key photocyclization step, an unusual regioselectivity at the position ortho to the nitro group was discovered in the coupling of the o-nitroaniline functional units at the bay sites of PBI. Multifunctional building blocks8and9were condensed with a pyrenedione, a pyrenetetraone and a hexaketocyclohexane octahydrate respectively, to construct novel ladder-type conjugated compounds12,13and15, and their optical properties, electrochemical properties and thermal stabilities have been investigated. Space charge limited current (SCLC) indicated that the enlargement of conjugated planar can enhance the intermolecular charge transport by improving molecular arrangement in the thin films. These ladder conjugated molecules were preliminarily applied as electron acceptors and blended with P3HT as the donor to fabricate BHJ solar cells, which exhibited better performance than their reference compound PBI.Ladder conjugated molecules based on triphenodioxazine diimides33,34,35,36and37were synthesized by a facile method and their optical properties, electrochemical properties and thermal properties were also investigated. Compared with PBI ref., these compounds exhibited intensive absorption in the range of200-600nm. Photodecomposition experiments and thermal gravimetric analysis (TGA) indicated that these compounds have good photostabilities and thermal stabilities, and compounds33and36exhibit liquid-crystalline behavior. The space-charge-limited current (SCLC) devices fabricated via spin coating, they exhibited n-type semiconductor performances with intrinsic electron mobilities considerably higher than that of the PBI ref., and compound37showed the best electron mobility with3.9x10-3cm2V-1s-1. These characteristics qualified compounds33,34,35,36and37as attractive electron-transporting materials applicable in organic electronics.Perylene bisimides derivatives40,41,42,43and44were synthesized by introducing substituents at the2,5,8,11-positions of the perylene core under Ir-catalysis and their optical properties, electrochemical properties and thermal stabilities have been discussed. Compared to reference compound38, hypsochromic shifts in the absorption and emission were observed for the derivatives40and41and the tetrachloro derivative40shows a greater shift than the tetrabromo one41. Their LUMO values are-4.18eV and-4.16eV, which are significant low than reference compound38. By introducing phenyl, thienyl and carbazolyl at the2,5,8,11-positions, the absorption bands show a bathochromic shift and the energy gaps become narrow when compared to the reference compound38. Their electron-transporting mobilities were investigated by SCLC method and compound43show the best result which reaches4.88×10-4cm2V-1s-1.Seven perylene bisimide derivatives46,47,48,49,50,51and52with side chains of L-aminopropanoic acid ester were designed and synthesized. Their liquid-crystal characters and thermal stabilities were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and thermal gravimetric analysis (TGA). The results indicated that all of the seven compounds have good thermal stability with5%decomposition temperatures (Td) higher than350℃, Compounds50,51and52exhibit liquid-crystalline behaviors with wide temperature range. Their melting points would rise as the side chains grow, but the temperature ranges of their liquid-crystalline become narrow. SCLC measurement indicated that compounds50,51and52which exhibit liquid-crystalline behaviors, showed better charge-transporting mobilities, which was up to1.90×10-3cm2V-1s-1for compound51.