Synthesis, Property And Near-infrared OLEDs Study Of Several Phthalocyanines

Since C.W.Tang has reported high brightness sandwich organic light-emitting devices (OLEDs)with low operating voltage for the first time in 1987,OLEDs have received more and more attentions because of it's merits such as:light weight,thin thickness,low cost, broad visual angle,fast response speed,active emitting,low energy consume,high brightness and efficiency,broad operating temperature,more choice of materials,availability for full color display and flexible display,etc.Compared with visible OLEDs it is just the start to study on near-infrared(NIR)OLEDs which has important applications in biology detection, photocommunication and military.Most efforts have been focused on metal-organic complexes based on several trivalent rare earth ions like,e.g.,erbium(Er³⁺),neodymium (Nd³⁺)or praseodymium(pr³⁺).Only a few organic materials containing no rare earth ions have shown EL characteristic at wavelengths longer than 1/μm.There is a substantial problem as regards the emitting quantum efficiency because of the following reasons:â…°)The EL originate from the f-f transition of rare earth ions,which is a parity-forbidden process,â…±)The NIR emission was near-field deactivation by the host associated with coupling of the optically excited state to the vibrations(such as O-H and C,H et al.)of the organic molecule or polymer,â…²)The ligand-sensitization scheme observed for the optical excitation of the organic ligands has not been confirmed to occur in current excitation.To realize the ligand-sensitization scheme in the current excitation,carriers must be injected into the HOMO (Highest Occupied Molecular Orbital)and LUMO(Lower Unoccupied Molecular Orbital)of organic ligands.Since the bandgap of organic ligands is normally large,the effective injection Of carriers into organic ligands is difficult to achieve and so the electroluminescence(EL) efficiency thus generated becomes low.To search organic infrared emissive materials containing no rare earth ions has become a new challenge.It has been realized that CuPc crystal photoluminescence focous at 1.1μm on previous literature.But its lower efficiency due to aggregation confines its luther utilities.In this paper, a copper-tetra(2-isopropyl-5-methylphenoxy)phthalocyanine(4-CuPc)is synthesized and utilized in near-infrared OLEDs.Phenoxy-substitution is synthesized to reduce the aggregation effect in order to enhance the quantum efficiency.Room-temperature electrophosphorescence was observed at about 1.1μm due to the T₁-S₀ transition of the 4-CuPc.The OLEDs of the type A:ITO/4-CuPc / A1,B:ITO/NPB/4-CuPc/BCP/Alq₃/AI, C:ITO/NPB/4-CuPc:Alq₃/BCP/Alq₃/ Al,D:ITO/NPB/4-CuPc:CBP/BCP/Alq₃/ Al,E: ITO/NPB/4-CuPc:Alq₃/TPBi/Al,F:ITO/NPB/4-CuPc:Alq₃:DCM/TPBi/A are fabricated by vacuum evaporating.Photoelectric properties show that all devices(except A)emit electrophosphorescence at about 1.1μm but no electrofluorescence.The reason may be the effect of heavy atom of Cu.This effect enhances the electons or holes transition probality between singlet and triplet states which induces the phosphorescence emitting.The emitting intensity of devices D and F is higher than others.The reason may be come from the overlap between the PL spectrum of CBP(4,4'-N,N'-dicarbazole-biphenyl),DCM (4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminost- yry)-4H-pyran)and the B,Q band of the 4-CuPc respectively.We also study the mechanism of energy transfer.The results indicate that in the device D F(o|¨)rster and Dexter energy transfer play minor roles and direct charge trapping appears to be the dominated mechanism;in the device F DCM as an emitting assist dopant plays a major role.EL intensity of the devices based on CuPc and 4-CuPc are compared.The result shows that EL intensity of the device based on 4-CuPc is higher.The external quantum efficiency of device F is evaluated at last. The synthesis and characterization ofβ-Tetra-(2-isopropyl-5-methylphenoxylphthalocyaninato)titanium(â…£)(4-TiOPc)are described and its electrochemistry,Spectroelectrochemistry,UV/Vis spectrum and PL spectrum are studied as well.The compound is sufficiently characterized by MS,¹H NMR, UV/Vis spectrum,elemental analysis,which are agreement with the proposed structures.The proposed EL characteristics are discussed by electrochemistry and spectroelectrochemistry. Due to the steric hindrance origining from the phenoxyl,this TiOPc are not readily aggregated in solution or solid.The chemical calculation results obtained from the software Chem 3D Ultra 11.0 used for the calculation of the minimum potential energy of this TiOPc that phenoxyl substituents can effectively enlarge the face-to-face distance among Pc molecules.This TiOPC have wonderful solubilities in chloroform(CHCl₃),dichloromethane (CH₂Cl₂),tetrahydrogenfuran(THF),toluene,benzene which make the coating method of OLEDs prepare accessible.We prepare the OLEDs with the type of ITO/PVK: 4-TiOPc/BCP/LiF/Al.The results show that the wavelength of electroluminescence is about 1050nm and the intensity varies with the change of 4-TiOPc concentration.The optimum concentration is 30 wt%.We also give out the reason.Being a very important compound,more than 10000 types of phthalocyanines have been discovered until now.But among all these phthalocyanines compounds,only 200 types have crystal.In this dissertation,we study the crystal growth of aza-CuPc which has been synthesized for 40 years.After two years of unremitting efforts,we obtained aza-CuPc single crystals using the unsealed evaporation method with assisted solvent and analysed the crystal structure.The most length of the crystal is 1mm;most of the single crystal is about 10～20μm long.The structure parameter was measured by synchrocyclotron X resource.The Japanese scientist had used 1000KV accelerate voltage TEM to obtain the structure image of CuPc by substituting H atom by heavy atom Cl in the 1980s last century.In this paper we have a try to access the structure image of aza-CuPc.We prepare the specimen with three methods:rubbing,evaporating and sectioning.Compared with simulation image and diffraction pattern the observation of project image of aza-CuPc with the electron beam parallel b axis give out an image included the structure message.