Design, Synthesis And Properties Of4-styryltriphenylamine-based Model Compounds As Electron Transfer

In recent years, the investigation of the novel organic photovoltaic materials isone of the most crucial factors for organic solar cells (OSC). Triphenylaminederivatives have been widely studied as one potential material for solar cellapplication due to its high extinction coefficient, excellent hole mobility and strongelectron-donor ability.In this paper we investigate the spectral properties and substituent effects of4-styryltriphenylamine-based (MTPA) derivatives of which the HOMO-LUMOtransition involves intramolecular charge transfer (ICT) from the triphenylamine tothe phenylene moiety. The photophysical processes show that nitro and cyano acetylgroup at the phenynylene moiety may lead to an enhanced ICT character whichchanges the decay of the singlet excited states.Efficient conversion of sunlight requires a photogeneration of long-lived ch-arge separated states that are capable of producing applicable photocurrents ordriving multi-electron chemistry of fuel synthesis. Considering the electron-acce-ptance ability and possible separated conjugation structure of an electron-deficie-nt heterocycles, a triazine cycle is introduced to MTPA. The results indicate t-hat the obtained organic semiconductor1-(4-(3,5-dichlorotriazin)aminophenyl)-2(4-N,N’-di(methylphenyl)phenylamino)ethylene (MTPA-TRC) can not only lead toan enhanced ICT effect but also make it a possible to achieve the photoinduce-d electron transfer. The lifetime of charge separated state MTPA+.-TRC-.of thissemiconductor is80ns.Metal-free anthraquinone derivative is introduced to MTPA-TRC, reportingan ambipolar organic semiconductor4,4’-dimethyl-4‖-(4-(4-chloro-6-(2-(9,10-dioxoanthracen-1-ylamino)ethylamino)-1,3,5-triazin-2-ylamino)styryl)triphenylamine(MTPA-TRC-AEAQ) designed to form a donor-acceptor1-acceptor2architect-ure with cascade electronic energy levels. The lifetime of charge separated stat-e MTPA.+-TRC-AEAQ.-of this semiconductor is elongated to650ns.Metal-free tetraporphyrin (HTPP) is combined with MTPA-TRC, the obta-ined ambipolar organic semiconductor4,4’-dimethyl-4‖-(4-(4-chloro-6-(4-(10,15,20-triphenylporphyrin)phenyl)amino-1,3,5-triazin-2-ylamino)styryl)triphenylamine(MTPAt-HTPP) is revealed with a D-A structure not the D-A1-A2structure, where the TRC module only plays a role of linker to join MTPA and HTPPmodules together. The electron transfer process in MTPAt-HTPP happens fromLUMO of MTPA module directly to HTPP module because the LUMO of TR-C module is lower than that HTPP module, causing a very short lifetime of c-harge-separated states. Comparing the different photophysical processes reportedin this paper, we reveal the importance of the energy levels of different modu-les, which determine the photoinduced electron transfer pathway, and thereforeinfluence the lifetime of charge-separated states.(E)-di(4-(4-(N,N’-dimethylphenyl)amino-phenylethenyl)phenyl)nitrene (MTP-AAZO) and (E)-di(4-(4-(N,N’-diphenyl)amino-phenylethenyl)phenyl)nitrene (TP-AAZO) are investigated, the results show that azo group at the azobenzenemoiety can not only lead to an enhanced ICT character which changes the dec-ay of the singlet excited states, but also the high conductivity in solution, suc-h as the conductivity of MTPAAZO in methylsulfonic acid is106.7mS/cm(Concentration:0.01mol/L). These novel materials may apply in optoelec-tronic devices or electric conduction.