Synthesis And Photoelectronic Properties Of Dibenzothiophene-s,s-dioxide Derivatives And Polymers

Compared to inorganic photoelectric functional materials, organic materials take many advantages of light weight, cheapness, easy to change the energy gap, kinds of chemical structure, solution processing and so on, which give wide applications in organic light-emitting diodes(OLED), organic photovoltaic(OPV), organic field effect transisitor(OFET).Dibenzothiophene-S,S-dioxide(SO) is an electron-withdrawing moiety with rigid and planar structure. It has high fluorescence. The sulfur atoms are at the highest valence, which leads to the good electronic affinity and anti-oxidation properties. However, there also exists several disadvantages for SO moiety, such as the smaller conjugated plane, the poor active reaction spots and solubility, which limit its application in OLED. Considering to its merits and drawbacks, dibenzothiophene-S,S-dioxide derivatives were synthetized in this thesis.Small molecules owned larger conjugated plane, better solubility, several active reaction spot S,Stable chemical structure as well as excellent fluorescence. Then the derivative units were drawn into the polymer main chains in order to improve the electronic transmission and fluorescence efficiency, which was good for the fabrication of high efficient devices.1) FBT, FBTO, Cz BT and Cz BTO, which were made from fluorene and 2, 7-carbazole, were synthetised. The rigid structure of small molecules led to excellent thermal stability with the decomposition temperature covered over 350 ℃ and the melting point of Cz BTO at 280 ℃. The small molecules realized a emission from ultraviolet to deep blue. The HOMO and LUMO levels of FBTO and Cz BTO were lower than those of FBT and Cz BTO.The energy gap of FBTO became narrower than that of FBT while the energy gap of Cz BTO became narrower than that of Cz BT, which was in line with the electrochemical properties of cyclic voltammetry.2) ICz BT,which were made from 3, 9-indolo[3,2-b]carbazole, were synthetised. ICz BT possessed rigid plane and proper energy gap. indolo[3,2-b]carbazole unit led to excellent hole transportation and the fused rings endowed super stability of chemical structure. The OFET devices performed well with a maximum hole mobility close to 0.6 cm2/(Vs), a low threshold voltage close to 0 V and current switch ratio up to 106. Devices exhibited super stability when they were laid outside for several days.Also the hole mobility remained unchanged with succession operation for an hour.3) Light emitting polymers containing fluorene based dibenzothiophene-S,S-dioxide derivatives(FSO) owned excellent thermal stability and high fluorescence quantum efficiency(QPL). Blue fluorescence materials and green fluorescence materials realized a QPL of 70 % and 87 %. The single layer devices for blue fluorescence realized a low Von of 2.8 V. After the addition of PVK layer, device performances became better obviously. The single layer devices for green fluorescence realized a low Von of 2.7 V. And the green polymers realized a emission from blue area to green area by changing the FSO proportion. The single layer devices for red fluorescence realized a low Von of 3.2 V and the device performances were good.4) Light emitting polymers containing carbazole based dibenzothiophene-S,S-dioxide derivatives(Cz SO) owned excellent thermal stability. The single layer devices for blue fluorescence realized a low Von of 3.5 V. The tortile structure of Cz SO unit weakened the intermolecular charge transfer(ICT) effect and restrained red-shift of the spectra.So devices obtained a deep blue CIE of(0.15, 0.10). The green materials realized a QPL of 94 %. The single layer devices for green fluorescence realized a low Von of 3.2 V. The tortile structure of Cz SO unit restrained red-shift of the spectra. So devices obtained a green CIE of(0.34, 0.58). The single layer devices for red fluorescence realized a low Von of 3.7 V and the device performances were better after the device structures were optimized.