Study On Synthesis And Optoelectronic Properties Of Pentacene Derivatives

Among organic semiconductor materials, pentacene has excellent carrier transport properties and is considered as one of the most promising materials. Thus, it has become a research hotspot in recent years. But it also has the disadvantage of poor solubility and stability. In order to improve its performance, this paper studies the synthesis and photoelectric properties of seven pentacene derivatives 6,13-bis(phenyl)pentacene, 6,13-bis(3-methylphenyl)pentacene, 6,13-bis(4-butylphenyl)pentacene,6,13-bis(1-hexynyl)pentacene,6,13-bis(phenylethynyl)pentacene,6,13-bi-s(3-methylphenylethynyl)pentacene and 6,13-bis(4-butylphenylethynyl)pentacene. Among these compounds, 6,13-bis(3-methylphenyl)pentacene and 6,13-bis(4-butylph-enylethynyl)pentacene were synthesized for the first time. The photoelectric properties of 6,13-bis(4-butylphenyl)pentacene was studied for the first time.In this paper, the theoretical studies on the seven pentacene derivatives were proformed by B3LYP/6-31G(d) with Gaussian 03 software to optimize their ground state geometry, bandgap, frontier molecular orbitals, ionization energy, electron affinity, and reorganization energy. The results suggested that these seven moleules all had lower energy gap than pentacene(2.21 eV), and the HOMO, LUMO, ionization energy, electron affinity energy and reorganization energy equivalent or better than pentacene. Then the synthesis of these pentacene derivatives were studied: 6,13-pentacenequinone and organic lithium were used as materials to prepare 6,13-dihydropentacene at 0?, and pentacene derivatives were synthesized with SnCl2/HCl as reducing agent to reduce 6,13-dihydropentacene at room temperature. And 6,13-bis(phenyl)pentacene, 6,13-bis(3-methyl)pentacene, 6,13-bis(4-butylphenyl)pentacene, 6,13-bis(1-hexynyl)pentacene, 6,13-bis(phenylethynyl)pentacene were synthesized in 65%, 72%, 69%, 78%, 81% yield respectively. Their structures were characterized by NMR. Then thermal stability, photochemical properties, electronic structures of these five compounds were investigated by using TGA, cyclic voltammetry and UV-vis. which showed that 6,13-bis(phenylethynyl)pentacene exhibited the longest wavelength absorption(710 nm) and the samllest band gap(1.746eV).At the same time, it had a high HOMO(-5.041 eV)and the lowest LUMO(-3.295 eV). These results suggested that this compound should have strongest carrier injection and transmission ability among these five pentacene derivatives. The results were consistent with the calculation results. In addition,the decomposition time of this compound in solution under air conditions was more than three days and the thermal decomposition temperature reached 442?. So this compound also showed a good stability. Finally, this compond was used to fabricate thin-film OFET and showed high mobilities of 0.07 cm2/Vs(with VTH=-10 V and ION/OFF = 102). Therefore, it can be used as organic semiconductor material with excellent performance in the future.