Synthesis And Optical-Electrical Property Of Fused Perylene Diimides-Carbazole Organic Semiconductors

Perylene diimides(PDIs) organic semiconductors have large conjugated structure and rigid plane, excellent photochemical and thermal stability, strong electron-accepting character, near-unity fluorescence quantum yields, facile modified structure, which allow PDIs to be used in many electronic and optical applications, such as organic field-effect transistors(OFETs), organic solar cells, photovoltaic devices. There are variety of PDIs organic semiconductors materials, including small molecules and polymers. However, studies about extending the ring of PDIs and their ladder conjugated polymers are rare. Moreover, the poor solubility of PDIs is still the obstacle of synthesis and applications.In this paper, we synthesized a series of soluble, conjugated ladder oligomers of fused perylene diimides-carbazole Y1, Y2, Y3, Y4, Y5, which have the structure of D-A-D, D-A-D, A-D-A, D-A, A-D-A. Then we synthesized a kind of ladder conjugated polymer with excellent solubility via introducing PDIs and carbazole all substituted in N position by long alkyl with side chain and studied their electronic and optical properties.Soluble intermediate 3,4,9,10-tetra(n-butoxy-carbonyl)-perylene was introduced in synthesis process. This method can efficiently obtain two kinds of fused perylene diimides-carbarole conjugated oligomers Y1 and Y2 substituted in N position with linear alkyl chain and successfully separated them in synthesis process. Compared to PDI1, Y1, Y2, Y3, Y4 have wider absorption range in CH2Cl2 and longer absorption wavelength, about 100 nm more than PDI1. Their fluorescence spectrum have a red shift of 83-110 nm. electrochemical data show that they have higher HOMO and LUMO energy level. Their structures are calculated with Gaussian 09 package, which show that they all own excellent planarity and they are a kind of oligomers with large conjugated plane.The third-order nonlinear properties of Y1, Y2, Y3, Y4 and PDI1 are determined by open/close aperture Z-scan measurements. They have similar third-order nonlinear susceptibilityχ(3), moreover, the data of Y1, Y3 and Y4 is a little bigger than PDI1. However, their two-photon absorption (TPA) character exist great difference. The TPA cross section Y1, Y2 and Y4 is 4 folds of PDI1 and Y3 with two PDIs is 6 folds of PDI1. All the data show that PDIs organic semiconductors have great potential in TPA field and more PDIs organic semiconductors with TPA character should be developed.A kind of soluble fused perylene diimides-carbazole conjugated polymer T1 was synthesized via new photocyclization method. T1 have wide and strong absorption between 250 and 650 nm and its molar extinction coefficient can reach to 2.1×104 M-1 cm-1. It has strong fluorescence peak at 643 nm and its fluorescence quantum yields reach to 0.1. Electrochemical data show that they have higher HOMO and LUMO. It can provide reference for the synthesis of soluble ladder conjugated polymers and it's competitive as candidate of solution processable semiconductor.