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Fabrication And Characterization Of ITO Conductive Substrate And Organic Optoelectronic Devices

Posted on:2009-10-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:H LinFull Text:PDF
GTID:1118360275980068Subject:Optical Engineering
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Since Tang et al at Eastmank Kodak firstly demonstrated an organic bilayerheterojunction (HJ) cell with high performance in 1986,organic optoelectronic deviceshave attracted great interest in academic and industrial field as a result of their highlypotential applications.So far,many organic small molecular devices have been studied,e.g.organic light-emitting diodes (OLEDs),organic thin film transistor (OTFT),organic photovoltaic (OPV) cell and organic laser.OLEDs as illumination source andbacklight for fiat panel display,possess many advantages,e.g.,self-emission,fastresponse,full solid device,easy fabrication,high efficiency,wide view-angle,ultrathinthickness.Therefore,OLEDs are considered as the most ideal and potential displaytechnology in 21st century.Compared to inorganic PV cell,OPVs have beenrecognized for their potential use in large-area,flexible,and low cost photovoltaicapplications asa renewable energy source.However,currently there are also several shortcomings to prevent organicoptoelectronic devices from large scale commercial application such as highfabrication cost,low power efficiency and indistinct understanding about devicemechanism.Aiming at those problems,in this word,some basic and systematic workshave been performed to focus on the fabrication process to obtain high performancerigid and flexible OLED and high efficiency OPVs.The main works in this thesis areas following:1.ITO thin films with high optical transparency and electrical conductivity werefabricated by DC magnetron sputtering method with the assistance of tiny water vaporduring deposition process.The parameters of water partial pressure,total pressure,substrate temperature,oxygen flow rate and sputtering power were scrutinized withrespect to their role in the texturing process,and orthogonal test table L18 (35) wasdesigned to carried out the systematic study.Sheet resistance,transmittance,atomicforce microscope,and X-ray diffraction were employed to characterize the ITO films.The results showed that the transmission of 100 nm ITO conductive substrate wasaround 83% and square resistivity was below 53Ω/□.The film was used as the transparent anode to fabricate an inverted top-emitting organic light-emitting device(IT-OLED) with a structure of Mg:Ag/Alq (40 nm)/NPB (15 nm)/CuPc (x nm)/ITOanode (100 nm),where the film thickness of CuPc was optimized.It was found that theluminance of IT-OLED with 15 nm of CuPc layer was 526 cd/m2 at 14 V.2.ITO films were fabricated on flexible substrate using a DC magnetronsputtering process at low temperature with the introducing of tiny water vapor.Thecorrelation of deposition condition and ITO film properties was systematicallyinvestigated.The optimized parameters of sputtering ITO film with thickness of 100nm are as follows:substrate temperature 50℃,DC power 100 W,and depositionpressure 2 mTorr.To enhance the adhesion of ITO film on flexible substrate,aUV-curable resin was introduced as a buffer layer between polymeric plastic substrateand ITO film.Flexible OLED with a structure of PET/buffer layer/ITO/NPB/Alq/Mg:Ag was fabricated.A maximum luminance of 3286 cd/m2 at 12 V was achieved.3.The structure and fabrication process of transparent cathode for transparentOLED were investigated.Computer aided design using Matlab based on matrix opticstheory was developed for the optimization of index match layer.The FOLED with astructure of ITO/CuPc (20 nm)/NPB (30 nm)/Alq (40 nm)/LiF (1 nm)/Al (1 nm)/Ag(24 nm)/Alq (50 nm) was fabricated.A maximum luminance of 4536 cd/m2 at 15Vwas obtained.4.The influence of film thickness of CuPc and C60 layer in single heterojunctionorganic solar cell was systematically investigated.Three different exciton blockingmaterials including BCP,Alq and CuPc were used in organic solar cell with a structureof ITO/CuPc/C60/EBL/Ag.The influence of exciton blocking materials on deviceefficiency was discussed in detail.5.A novel phosphor of bis[2-(4-tertbutylphenyl) benzothi azolato-N,C2,]iridiumm (acetylacetonate) [(t-bt)2Ir(acac)] was doped in CuPc as a donor to fabricate amore efficient organic solar cell.The device with a structure of ITO/CuPc:x%(t-bt)2Ir(acac) /C60/BCP/Ag,ITO/(t-bt)2Ir(acac)/CuPc/C60/BCP/Ag and ITO/CuPc/(t-bt)2Ir(acac)/C60/BCP/Ag were fabricated.The function of triplet materials on deviceefficiency was explained in theory.In summary,this work paves the way for high-efficiency flexible optoelectronicdevice based on the fabrication of rigid substrate as well as flexible substrate,and some effective preliminary works have been carried out on high performance organicsolar cell.We are optimistic that flexible organic solar cell with high efficiency can beachieved using our flexible substrate in the very near future.
Keywords/Search Tags:Indium tin oxide (ITO), DC magnetron sputtering, Transparent OLED, Phosphorescent material, Organic solar cell, Flexible substrate
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