有机光电半导体材料及其未来之应用

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1、有機光電半導體材料及其有機光電半導體材料及其未來之應用未來之應用 Institute of Electro-Optical Science and Engineering,National Cheng Kung University,Tainan,Taiwan 701成功大學成功大學 光電科學與工程研究所光電科學與工程研究所01/16/2007郭郭 宗宗 枋枋 助理教授助理教授T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering2Outlines Semiconductors Organic semiconductors(e

2、nergy and delocalization of charge carriers)OLEDs and PLEDs 基礎原理和應用 Organnic photovoltaic and solar cells ConclusionsT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering3Fundamental science of inorganic semiconductorsT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering4Typical Semi

3、conducting MaterialsT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering5Energy Band Diagram of a conductor,semiconductor,and insulator(a)a conductor(b)a semiconductor(c)an insulatorT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering6Beginning of orgnaic semiconductor(bonding)Side

4、-by-Side BondingT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering7Conjugated(共軛共軛):alternatively double-single bondsCHCHCHCHCHCHCHHCCHHCCHHCCHHCCHHCCHHCCHHCC雙鍵雙鍵單鍵單鍵 T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering8Bang Gap of Polyacetylene.Band GapT.-F.GuoNCKU Institite of

5、Electro-Optical Science&Engineering9Conjugated polymerSigma bondDelocalized electron cloudhttp:/www.cdtltd.co.ukAlternating single-double bondsT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering10Creating new materials from old materialsnEg=2.4 eVPPVOR1nOEg=2.1 eVR2R1nEg=2.4 eVR2nEg=3.0 eV

6、PPPnEg=1.4 eVPAThrough the structure engineering,polymers with different emitting colors were synthesized.T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering11Delocalization of Charge Carriers in PolyacetyleneLocalized!Charge cannot go anywhere!Delocalized!Charge carriers can move around!T

7、.-F.GuoNCKU Institite of Electro-Optical Science&Engineering12Delocalization and Transport of Charge CarriersT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering13Conjugated Polymers:Basic Materials and Chemistry Conduction polymers:Polyacetylene,Polyaniline,PEDOT/PSS etc.Semiconducting pol

8、ymers:Polythiophenes,Oligothiophenes etc.Light-emitting/Photovoltaic Polymers:Poly-(para-phenylene-vinylene),Poly(para-phenylene),Polyfluorene etc.T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering14Scientific Interest in Organic Materials 1950s steady work on crystalline organics starts

9、1970s organic photoconductors(Xerography)1980s organic non-linear optical materials 1987 Kodak first published the efficient organic light-emitting devices(OLED)1990 Cambridge groups publish the first polymer light-emitting diodes(PLED)Since then,the field has dramatically expanded both commercially

10、 and scientifically,including OLED,PLED,transistors,potovoltaic,solar cells T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering15What are the OLEDs?Invented by Dr.Ching W Tang（鄧青雲博士）(kodak)1987年OLED 全名叫做有機發光二極體(Organic Light-Emitting Diode)部分國外又稱 OEL為有機電激光顯示(Organic Electroluminescence Dis

11、play)T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering16OLED Basic Device ConfigurationDouble layers structure 電洞傳輸層-Hole Transport(injection)Layer(HTL)電子傳輸層 Electron Transport Layer(ETL)發光層-Emitting Layer(EML)T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering17First OLED Inve

12、nted by Dr.Ching W Tang(kodak)1987T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering18Absorption,Fluorescence&Phosphorescence ProcessT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering19Singlet excitonsTriplet excitonsh1h2fluorescencenon-radiationheate-/h+dissociationrecombinati

13、onIntersystem crossingT-T annihilationphosphorescencedissociationcarrier separationcarrier injectionPhotophysics processground stateT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering20Operation of OLEDsGlass or PET substrateITOETLHTL+_+_+_ _+CathodeAnodeT.-F.GuoNCKU Institite of Electro-O

14、ptical Science&Engineering21Electroluminescence of O/PLEDSingle layer deviceDouble layer devicePLEDDouble layer deviceOLEDT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering22carrierinjectioncarriermigration(+)(-)(+)(-)(+)(-)221/+-3 symmetric statesTriplets1 antisymmetric stateSinglet1/+or

15、singlettriplethole(+)electron(-)exciton(*)Mechanism of ElectroluminescenceT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering23Intersystem crossing(ISC)S0S1T1Ground stateFluorescencePhosphorescenceFluorescence and PhosphorescenceDecay from singlet allowed by symmetry:fast and often efficie

16、nt.Decay from triplet disallowed by symmetry:slow and usually inefficient.25%75%Singlet excitonTriplet excitonT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering24Device preparationITO/Glass substrateOrganic materialsVacuum10-5 torrLecture note of Prof.Chou,NTU Phys.T.-F.GuoNCKU Institite

17、of Electro-Optical Science&Engineering25What are PLEDs?Invented by Richard.H.Friend(University of Cambridge,Cavendish Laboratory)1990年PLED 全名叫做高分子發光二極體(Polymer Light-Emitting Diode)Usually for single layer device configurationT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering26First PLED

18、Invented by Richard.H.Friend(Cambridge University,Cavendish Laboratory)1990They used Al as the cathode material at that time.T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering27Synthetic Route to PPVJ.H.Burroughes,D.D.C.Bradley,A.R.Brown,R.N.Marks,K.Mackay,R.H.Friend,P.L.Burns,and A.B.Hol

19、mes,Nature,347,539(1990).T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering28Schematic Energy Level Diagram T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering29Processing for the fabrication of a typical PLEDPre-cleaned ITO/glass substrateSpin coating PEDOT layer&baking*OO*n Eg

20、=2.1eVOrange-redor yellowMEH-PPVSpin coating MEH-PPV layer&bakingCathode depositionOOSSOOOOSSOOOOSn+SO3-nSO3HmPEDOT:PSST.-F.GuoNCKU Institite of Electro-Optical Science&Engineering30PLED Devices at NCKUBefore biasBiased deviceT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering31Why they ar

21、e so important?http:/www.nobel.se/chemistry/laureates/2000/illpres/7.htmlSelf-luminescentNo viewing angle limitationThin,Light weightLow operation voltageFlexible substrate applicationT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering3220 inches,amorphous Si,active matrix,full color OLED

22、displayWXGA(1280 x 768 pixels),25 W,300 cd/m2,CMO 03/12/2003Recent progress of EL PanelsKodak digital camera,available on April 2003Ink-jet printed EL display,Toshiba and Epson 2002T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering33Reasons for organic solar cellsOrganic solar cells:moder

23、ate efficiencies and very low cost Inorganic photovoltaic cellS.E.Shaheen,D.S.Ginley,G.E.Jabbour,Mrs.Bull.,30,pp.10-18(2005).T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering34A Flexible,printed plastic solar cell with high efficiency made by SIMENS AGhFlexible Donor-acceptor type solar

24、cellsT.-F.GuoNCKU Institite of Electro-Optical Science&Engineering35Working principle of organic solar cellA Donor-Acceptor type bulk heterojunction solar cellMetal electrode(Al,Ca/Al etc.)he-h+EFHOMO PCBMLUMO AcceptorLUMO DonorHOMO DonorITO/PEDOTe-h+h+h+e-Donor+AcceptorMetal electrodeITOhOCH2OSSSSn

25、/4Donor-P3HTAcceptor-PCBMMPPMPPocscFFVJVJscocoutpowerininFFJVPPPJ(photo-current density)V(Bias)curves for devices with Al and Ca/Al as the cathodes CathodematerialVoc(V)Jsc(mA/cm2)Vmpp(V)Jmpp(mA/cm2)Fill FactorpowerAl0.564-8.1530.426-3.6910.4232.142%Ca/Al0.544-12.9330.382-10.4330.5664.383%Incident p

26、ower of 90mW/cm2T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering37Conclusions Organic electronics乃是一項跨領域的學科，涵蓋半導體元件物理、基礎物理、電機、化學、材料而基礎物理化學的基礎更是為重要。Flexible devices(軟性電子)將是未來科技的一項研究重點，此乃organic electronics之發展強項。T.-F.GuoNCKU Institite of Electro-Optical Science&Engineering38Future of Information Display