Pentacene is one of the most intensively studied systems among various organic semiconductors

for its relatively high field effect mobility and its ability to form ordered films.Nevertheless

pentacene suffers from the disadvantages of oxidative instability and

for display applications

a strong absorbance exists throughout the visible spectrum.Where photoinduced decomposition reactions could occur

this absorbance would make pentacene sensitive to most visible light.Compared to pentacene

there is an important small molecule semiconductor

that is thiophene-based materials exhibiting a variety of intraand intermolecular interactions-van der W aals interactions

weak hydrogen bandings

π-π stacking

sulfur-sulfur interactions-originating from the high polarizability of sulfur electrons in the thiophene rings.From the molecule structure

it can be analyzed that pentathienoacene(PTA) has high stability than pentacene owing to PTA's large band gap.These performances indicate PTA may have potential application in future organic electronics.However

the report on its application and basal physical characteristic obtained from experiment is few

and its theoretic research is much less.Quantum chemistry calculation can provide credible and valuable information for molecule study.In this paper

PTA molecule was calculated

including geometry model

infrared spectra

Raman spectra

HOMO-LUMO gap and the frontier molecular orbits by density function theory(DFT) for the first time

so the results can provide some reference informations for the future organic devices materials design theoretically.The infrared spectra and Raman spectra have been discussed and the spectra peaks of pentathienoacene were identified

the above datum on Raman spectra of PTA can provide the valuable reference for the experiment on PTA molecule identified.And at the same time

the HOMO-LUMO gap is gained:3.86 eV

which is very close to the experimental result.The five strongest allowable singlet excited states have been studied by TDDFT.The results indicate that all the energies of excited states were located in ultraviolet region

so PTA molecule is relatively stable under the visible light illumination because photoinduced decomposition reactions can not occur.The transition electron is diverted from carbon atom to sulfur atom

which can be seen through the frontier molecular orbits of pentathienoacene.Moreover

the formation of π-delocalized band leads to increase PTA molecule conductival.The results indicate that pentathienoacene is a new kind of organic semiconductor material and has perfect luminescence and electrical properties

especially

PTA has higher stability than pentacene.