Organic Light Emitting Diode So Led
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Transcript of Organic Light Emitting Diode So Led
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OrganicLightEmittingDiodes(OLED)
Definition
Scientificresearchintheareaofsemiconductingorganicmaterialsastheactivesubstanceinlightemittingdiodes(LEDs)hasincreasedimmenselyduringthelastfourdecades.Organicsemiconductorswasfirstreportedinthe60:sandthenthematerialswhereonlyconsideredtobemerelyascientificcuriosity.(Theyarenamedorganicbecausetheyconsistprimarilyofcarbon,hydrogenandoxygen.).Howeverwhenitwasrecognizedintheeightiesthatmanyofthemarephotoconductiveundervisiblelight,industrialinterestswereattracted.Manymajorelectroniccompanies,suchasPhilipsandPioneer,aretodayinvestingaconsiderableamountofmoneyinthescienceoforganicelectronicandoptoelectronicdevices.Themajorreasonforthebigattentiontothesedevicesisthattheypossiblycouldbemuchmoreefficientthantodayscomponentswhenitcomestopowerconsumptionandproducedlight.Commonlightemitterstoday,LightEmittingDiodes
(LEDs)andordinarylightbulbsconsumemorepowerthanorganicdiodesdo.Andthestrivetodecreasepowerconsumptionisalwayssomethingofmatter.Otherreasonsfortheindustrialattentionarei.e.thateventuallyorganicfullcolordisplayswillreplacetodaysliquidcrystaldisplays(LCDs)usedinlaptopcomputersandmayevenonedayreplaceourordinaryCRT-screens.
Organiclight-emittingdevices(OLEDs)operateontheprincipleofconvertingelectricalenergyintolight,aphenomenonknownaselectroluminescence.Theyexploitthepropertiesofcertainorganicmaterialswhichemitlightwhenanelectriccurrentpassesthroughthem.Initssimplestform,anOLEDconsistsofalayerofthisluminescentmaterialsandwichedbetweentwoelectrodes.Whenanelectriccurrentispassedbetweentheelectrodes,throughtheorganiclayer,lightisemittedwithacolorthatdependsontheparticularmaterialused.Inordertoo
bservethelightemittedbyanOLED,atleastoneoftheelectrodesmustbetransparent.
WhenOLEDsareusedaspixelsinflatpaneldisplaystheyhavesomeadvantagesoverbacklitactive-matrixLCDdisplays-greaterviewingangle,lighterweight,andquickerresponse.Sinceonlythepartofthedisplaythatisactuallylitupconsumespower,themostefficientOLEDsavailabletodayuselesspower.Basedontheseadvantages,OLEDshavebeenproposedforawiderangeofdisplayapplicationsincludingmagnifiedmicrodisplays,wearable,head-mountedcomputers,digitalcameras,personaldigitalassistants,smartpagers,virtualrealitygames,andmobilephonesaswellasmedical,automotive,andotherindustrialapplications.
OLEDVersusLEDElectronically,OLEDissimilartoold-fashionedLEDs--putalowvoltageacrossthemandtheyglow.Butthat'sasfarasthesimilaritygoes:insteadofbeingmadeoutofsemiconductingmetals,OLEDsaremadefrompolymers,plasticsorothercarbon-containingcompounds.Thesecanbemadeverycheaplyandturnedintodeviceswithoutalltheexpensivepalaverthatgoeswithsemiconductorfabrication.
Light-emittingdiodes,baseduponsemiconductorssuchasGalliumArsenide,GalliumPhosphide,and,mostrecently,GalliumNitride,havebeenaroundsincethela
te'50s.Theyaremostlyusedasindicatorlamps,althoughtheywereusedincalculatorsbeforeliquidcrystals,andareusedinlargeadvertisingsigns,wheretheyarevaluedforverylonglifeandhighbrightness.SuchcrystallineLEDsar
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enotinexpensive,anditisverydifficulttointegratethemintosmallhigh-resolutiondisplays.
