8Multi-layer blade coating of organic semiconductors microngapmovingRapid evaporationPolymer solutionPolymer film (wet)GapPolymer film (dry)Appl. Phys. Lett. 93, (2008)ITO SubstrateHot plateEmissionlayerMulti-layer solution deposition for high efficiencyArbitrary solventLarge area uniformityLow material wasteCompatible with roll-to-roll processElectronblockingEmissiveHoleenergycathodeanode
9Blade coating for OLED and vertical transistor ITOHot plateITOHot plateOrganic layer4×4 cm2OLEDHot plateITOHot windHot plateITOJ. Appl. Phys. 110, (2011)
10Other applications RFID Pressure sensor array Short channel length Short carrier transit timeHigh frequencyApp. Phys. Lett. 95, (2009)
11Progress of SCLT performance enough for OLED driving 國科會 卓越領航計劃交大 特色計劃
12Enhancing the base control Appl. Phys. Lett., 97, , 2010
13Enhancing the base control Appl. Phys. Lett. 98, , 2011
142011 Breakthrough toward a real technology Jump in collector currentOrganic semiconductor blade coatingSelf-assembled monolayerPS sphere by blade coating
152011 Breakthrough toward a real technology Jump in collector currentOrganic semiconductor blade coatingSelf-assembled monolayerPS sphere by blade coating
16Conduction in Organic Semiconductors Van der Walls forces hold molecules togetherCharge transport is dependent on -bonding orbitals and quantum mechanical wave-function overlap (by hopping).Effective mobility increases with increasing temperature and increasing carrier concentrationSpace-charge-limited current:
17Anisotropic Transport Charge transport in most organic semiconductor including conjugated polymers is anisotropic. Field-effect hole mobility in P3HT is higher than 0.1 cm2/Vs along the polymer backbone and the - orbital stacking and is lower than 2×10-4 cm2/Vs along the insulating side chainE.g. P3HT: poly(3-hexylthiophene)
18Q: How to improve the output current in organic transistor ? A: Improving molecular packing in the right direction!For conventional FET:Current flows in lateral direction.Edge-on direction is required to obtain high mobility.Reported methods:Using high boiling point solvent to improve molecular packingUsing solvent annealing to improve molecular packingUsing SAM to control orientation !!
19SAM treatment in OFETs Nature 5, 222, 2006 SAMs (Self-Assemble Monolayers): HMDS and OTS on SiO2 for P3HT FETGateOxideP3HTSAMSD
20Our idea : SAM on vertical sidewalls Conditions:SAM: (a) HMDS and (b) OTSTop injection :using symmetric EC metal to reduce built-in potential barrierUsing MoO3/Al to adjust emitter work function as 5.3 eVCB by both spin coating and blade coating (without spinning)
21Results: improved pore filling After OTS treatment, pore surface becomes hydrophilicOTS treated, spin coatingSTD (no SAM), spin coatingSTD, blade coating
29Transistor Performance (Blade Coating PS Spheres) 小面積(1mm2)元件輸出特性On/off ratio ~ 40000大面積(1cm2)元件輸出特性On/off ratio ~ 5000
30Connected OLED/SCLT Al/MoO3 pattern Top Emitter Off state On state VEIEVBIBVCIC0.00E+004.43E-04-9.00E-011.16E-05-4.50E+00-4.60E-044.33E-041.09E-05-4.45E-04offVEIEVBIBVCIC0.00E+001.44E-045.21E-05-4.50E+00-1.96E-041.43E-045.07E-05-1.94E-04On stateOff stateTotal voltage : 6 V (across OLED and SCLT)ON state: Base voltage = -0.9 V; OFF state: Base voltage = 0 V42-b
31Other solution-processed OTFT Field-effect mobilityOperation voltageOn/off ratioChannel materialGate dielectric2005 [JACS]0.004< 2 V100P3HTPolymer dielectric CPVP-C6 (thickness nm)2005 [ APL]0.005< 2V200SAM2006 [Nature Material]> 20 V> 106PBTTTOTS-treated SiO22007 [OE]0.0173600Plasma oxidation on Al gate2007 [APL]0.2 ~ 1.8> 10 VTIPSHMDS-treated SiO22007 [JACS]0.1105Ion-gel gate dielectric (for top gate); gel solution mixed with stirring over 12 hrs2008 [Nature Materials, Adv. Mat.]22.214.171.124< 3 V104~105PQT-12F8T2Ion-gel gate dielectric (for top gate); slow process: solvent evaporated for 24 hrs and the ion-gel dried in vacuum over 2 days2008 [Nature Material, JACS, APL]1.5diF-TESADTPFBT-treated gold electrodes with HMDS-treated SiO22009 [Adv. Mat.]0.15> 30 V36700PETV12TPMMA, 500 nm2009 [ Adv. Mat.]0.34N/A2011 [ Adv. Mat.]7-11C8-BTBT or C10-DNTTCYTOP (Asahi Glass Co. for top-gate)2011 [AIP Advances]3.5C8-BTBTFTS-treated SiO2
32SummaryWith high output current , low operation voltage and high on/off current ratio, vertical transistor SCLT is one of the best solution processed transistor in the world.Blade coating is successfully demonstrated on OLED and SCLT. Particularly, blade coating PS spheres facilitates the roll-to-roll large area nanostructure colloidal lithography .Solution processed OLED can be switched on and off by SCLT within 1-V base voltage.
33Future WorkDevelop process for integrated solution-processed OLED/SCLT.Develop large-area array process for SCLT.Integrate large-area SCLT array with large-area OLED to realize low-cost e-book (based on blade coating process).Proposed process is introduced hereafter.
34Integrated OLED / SCLT Two Approaches: Fabricating OLED on top of SCLT Light emissionTwo Approaches:Fabricating OLED on top of SCLTConnecting large-area OLED with SCLT array panelHTLEMLEmitterBaseETLCollectorLiFPO-01-TBCBPP3HTPVPAlMoO3GlassNPBTBPiAgOLEDSCLTPEDOTCathodeLight emissionGlassOLEDGlass
35Proposed Large Area Process (示意圖,基板可放大) 100 um10 umTentative process to define the bottom metal electrode:Low-end lithography with lift-off process, blanket bar coating (similar to blade coating) or interference lithography
36Proposed Large Area Process (示意圖,基板可放大) 100 um10 um PVP coating and cross-linking 10-um wide PR line formation (low-end photolithography, blanket bar coating or interference lithography) PS spheres coating on PVP
37Proposed Large Area Process (示意圖,基板可放大) 100 um10 um Base metal deposition with PR lift-off processRemoving PS spheres by roller taping
38Proposed Large Area Process (示意圖,基板可放大) 100 um10 um Plasma etch through nanometer holesSAM treatment on nanometer holesP3HT coating
39Proposed Large Area Process (示意圖,基板可放大) 100 um10 um Passivation layer formationPixel contact via formation and metal coating (patterned by liftoff process)Then: fabricating large-area OLED on top of array panel or connecting array panel with OLED (on the other substrate)
40Demonstration PS sphere blade coating process. Solution processed OLED switched on and off by SCLT within 1-V base voltage.