Organic Electronics Two Stories Optical Electronics (Tfts) Solar Ce Lls (Charge Transport)

Comp arison with inorganic mat eri als

E C2H4 Co ndu cti o n B an d E

LUMO σ∗ ORGANIC Eg π∗ (an ti- b o ndin g orb it al) Ψ = 1 − p π* (ϕ1 ϕ2 ) k z 2 Vale nc e B a nd ELECTRONICS pz Ψ = 1 + HOMO (bon di n g orbi tal ) π ()ϕ1 ϕ 2 π 2 σ Discrete or Band

Inorga nic solids Organic solids

Bonding Ionic, Covalent, Metallic (2-4 Ionic or covalent within molecule, the solid eV) held together by Van der Waalsforces Deepak Gupta (<0.01 eV); solid behaviour therefore Materials & Metallurgical Engineering governed by molecule. Charge Electrons, holes, ions Polarons, exciton diffusion carriers Mobility 100-10000 cm 2/Vs 10 -6-1 cm 2/Vs

Organic Electronics Two Stories Optical Electronics (TFTs) Solar Ce lls (Charge transport)

Displays Illu mination Sou rces 1. Conducting Polymers: Charge transport in polymers (in one slide!) (Radiative Recombination/Generation and Charge transport) 2. OLED: Light emission upon charge injection (commercialization)

Two Flavours: 1. Small Molecules 2. Polymers

OLEDs Conducting Polymers

Invention at Kodak in 1987, a simple structure of two layers

2007

Cath od e Electr on Inj ecti on La ye r Hole Bl ocki ng L aye r ( op tio nal) Electr on T ra nsp or t L ay er Emissiv e Lay er Hole T ra nsp ort L aye r Hole Inj ecti on Lay er ITO Glass

MILESTONES 1.0 First Heterostructure OLED (bring voltage down) 2.0 Guest-Host Colour Tuning in 1989 (control colours) 3.0 Ir-Complexes based phosphorescent materials (nearly 100% efficiency) 4.0 Conductivity Doping (device operation at minimal voltage)

1 1.0 First Het erost ructu re OLE D ( brin g vo lt ag e dow n) Fluorescence and Phosphorescence Mg:A g, A g Alq3 Diami ne Excited states by injecting charge from electrodes ITO Glass LUMO - ITO Anode - Mg:Ag cathode S + + 1 Intersystem Crossing, ISC + Diamine HOMO Tang and Van Slyke, APL, 51, 913, 1987 •S represents Singlet Alq3 T1 State (S=0) ?, Phosphorescence, •T represents Triplet 2.0 Guest-Ho st Colour Tuning in 1989 ( co ntr ol c ol our s) X µs to s State (S=1) Mg:A g, A g Alq3 Dop ed Al q3 •Subscript o is ground So Diami ne Fluorescence, state, subscript 1 is ITO ns to ps excited state Glass

Flu or esc ent OLE D

Phos ph or esc ent OLE D

Tang, Van Slyke and Chen, J. Appl. Phys., 65, 3610, 1989

3.0 Ir- Complexes based phospho rescent material s (nearly 100% eff iciency ) 4.0 Conductivity Doping (device o peratio n at minimal vol tage)

At w h at is the p oten tia l ( v olt a ge) are carrier i nj ec te d ? Me an in g wh at a b out power ef fi cie nc y.

P-type doping Add acceptor whose LUMO is than HOMO of Matrix

gree n red bl ue

Operation at theoretically lowest voltage Source: M. Baldo, Ph.D. Dissertation, Princeton, 2001

2 0 03 OLED History January - Philips invents EL material to generate bo th red and g reen ligh t. Janu ary - Ko d ak, Sanyo in v est in activ e-matrix OLED production. http://www.oled-info.com/history Janu ary - Sany o Un v eils Mobile Phon e with Org anic EL Panel Desig n ed fo r KDDI, ann oun ces p lans to b u ild full-colo r OLED p rod u ction lin e. Febru ary - RiTd isplay land s mobile p hon e OLED o rd ers fro m Samsu n g and LGE. Febru ary - Ko d ak Licenses Sam su n g NEC Mobile Disp lay to Manu factu re Passiv e-Matrix OLED Disp lays. March - Ko d ak in trod u ces th e first d igital camera with an OLED scre en - th e Ko d ak Easy Share LS6 3 3 . March - IDTech develops 20-inch full-color OLED display. The Ea rly Years April - DuPont forges 'Olight' brand for emerging OLEDs. 1996 - CDT gives world's firstpublic demonstrationo f Light Emitting Poly mer d evices Ap ril - Sony testing 24-in ch OLED screen. 1 9 97 - UDC Demon strates Flexib le Flat Panel Disp lay Techn o logy May - AUO and UDC d evelo p 4 -inch, a-Si TFT b ackp lane-b ased, red p hosp horescent AMOLED. 1997 - Pioneer Electronic Produces EL Display with 26 0 ,000 Co lors May - Samsu n g NEC d evelops 6 5,0 00-colo r PM OLED mob ile phone d isp lay. 1998 - Kodak, Sanyo Show Full-Color Active Matrix Org anic Disp lay; First Colo r OEL Disp lay In creases Th re at to LCD Disp lay Do min ance May - Sony demon strated a 2 4 .2 in ch OLED p anel. 1 9 98 - Green Org anic LED Sh o ws Hig h Efficiency June - ERSO and Windell develop 10-inch LTPS TFT tech n o logy-b ased AM OLED d isp lay. 2 0 00 - Ritekp lans to mass p ro duce OLED June - Sony to invest nine billion yen to build OLED p rodu ction line. 2000 - Toshiba Corp. plans to produce (organic EL) p anels in 2001 September - AU Op tro n ics h as sh o wcas ed its 1 .93" AMOLED fo r Mo bile Ph one. 2000 - Motorola Grants OLED Technology Rights To Univ ersal Disp lay An d Takes Eq u ity Position September - Prin ceto n electrical eng in eers h ave in v ented a technique for making Organic Solar Cells that Could Lead To Wid esp read Use Of So lar Po wer. 2 0 00 - UDC and PPG Ind u stries Form Strategic Alliance for Development & Supply of Chemicals for OLED Man u factu rers Octo b er - Sany o Unveils Lo ng-Lastin g QVGA Org anic EL Panel fo r Cell Phon es. 2000 - Sanyo Electric to start mass production of colo r o rganic EL p anels in 2 001 Octo b er - Un iv isio n b egin s OLED pro ductio n . 2 0 00 - NEC, Samsu n g To Develo p Org anic Wireless Disp lays November - Tohoku Pioneer Corporation to Be First Man u factu rer to Use Un iv ersal Disp lay Co rporatio n's PHOLED Material in a Co mmer cial OLED Disp lay. 2000 - LG Electronics develops organic EL displays fo r mob ile g adgets No v ember - Un iv isio n sho wcases 6 5 ,0 0 0 -color mob ile ph one OLED su b -d isp lay. Dec ember - Un iv isio n reaches mon th ly capacity o f 6 ,000 OLED su b strates. 2 0 01 Dec ember - Ca sio Ventu res in to Org anic EL Panels Driv en by Amorpho u s Si TFT. February - Sony Develops World's Largest Full Color OLED (13 in ches d iagon ally with a reso lu tion of 800 x600 p ixels.) Ap ril - Un iv ersal Disp lay Co rporatio n and Son y Co rpo ratio n Announ ce Jo in t Develo p ment Ag reement Aimed at OLED Television Monitors. 2 0 04 April - Samsung Exhibits Color Organic EL LCD Panel fo r Mob ile Phones at CeBIT (1 3 2 by 162pix els). January - Opto Tech to invest NT$4.5 billion in four n ew OLED lin es in 2004 . May - Toshiba Develops World's First 260,000-Color Po lymer OLED. February - Philips 639 mobile phone applies PolyLED techn o log y in un iqu e 'Magic Mirror' disp lay. August - eMagin's OLED MicrodisplaySelected by Air Fo rce fo r F15 E Aircraft. March - GE Glo b al Resear ch Breaks Two Wo rld Record s For OLEDs As A Lighting Device. Demo Lighting Panel is Bigg est and Most Efficient Ev er Created. October - Sony Demonstrates 13-Inch, Full-Color OLED Proto typ e. March - NEC d ro p s its OLED busin ess . Octo b er - Un iv ersal Disp lay Co rp o ration and Samsu n g SDI An nounce Key Jo in t Develo p ment Ag reement. March - Ch i Mei Op to electro n ics Co rp . (CMO) h as ann o un ced a fu lly fun ctional p roto type o f a 20-in ch full-color OLED display - the largest Amorpheous Si TFT. Octo b er - Un iv ersal Disp lay Repo rts New Red Ph o sp h o rescent OLED Materials, Sig n ificant Po wer Efficiency Ad v ances. April - Teco Optronics to invest NT$300 million to build new PM OLED p lant. Octo b er - Samsu n g SDI Develo p s Wo rld's Larg est Org an ic Disp lay Panel (1 5.1 inch). Ap ril - RiT Disp lay sh ips mob ile phone OLED su b -d isp lays to Samsu n g, says p aper. No v ember - RiTd isp lay opens n ew colo r OLED/PLED facto ry . April - Seiko Epson Reveals 12.5-Inch Organic EL Pan el fo r Larg e TVs. April - RiT Display shipping OLED panels to Motorola. 2 0 02 May - Seiko Epson unveils first 40" colour OLED display. February - Samsung SDI develops 2.2-inch AM OLED for mob ile ph ones. May - Un iv ersal Disp lay Co rp o ration Announ ces Record -Breakin g Po wer Efficiencies fo r its Ph o sp horescent White OLED Technology. April - Philips Announces Industry's First Volume Ship ments o f Poly mer-Based OLED Mo d u les. May - Taiwan' s AU Begin s Mass Pro d u ction o f Org anic EL Panels. May - Ko d ak Anno unces Av ailability o f Evalu ation Kit Fo r Activ e-Matrix OLED Disp lay. May - Un iv ersal Disp lay Co rp o ration Unveils Gro u nd b reaking Flexible OLED Pro to typ e on Metallic Substrate. May - RiTdisplay reportedly receives orders for over o n e million mob ile ph one OLEDs. Ju n e - To ppan to v olu me p ro duce larg e-size OLED p anels. June - AU Optronics develops world's first OLED proto typ e combinin g a-Si TFT LCD techn olo gy. Ju n e - OLED-In fo is on-lin e, the web's first OLED co mmun ity site. June - Epson, CDT form polymer OLED production ventu re. September - Sony Starts Mass Production of Organic EL Disp lays, and released first a n ew clie PDA with a 3 .8 in 480 x 320 OLED screen. November - Pioneer Supplies OLED to LG Electronics fo r Cell Pho n es. October - LG.Philipsdevelops 20-inch OLED display. Dec ember - Du Po n t Disp lays and Un iversal Disp lay Co rp o ration Form Strategic Alliance to Develo p Next Gen eratio n Disp lays Co mbin ing Asp ects o f Small Mo lecule and November - OLED displays with 50,000h operating lifesp an fro m URT. Po ly mer OLEDs. No v ember - Seik o Ep son will commercializ e OLED TVs b y 2 0 0 7 . Dec ember - CDT IPOs, lists o n NASDAQ .

2 DISPLAYS 2 0 05 Janu ary - Samsu n g Electro n ics d evelo p s 21 -inch OLED fo r TVs, claims wo rld ' s larg est . Janu ary - Samsu n g SDI To d oub le the OLED o u tput . Eastman Kodak and Sanyo Electric; Janu ary - OLED Techn o lo gy Poised to Become Co re Bu sin ess fo r Daewo o Electro n ics . Febru ary - MP3-p layer d emand boo sts sales o f Taiwan OLED make rs . Active-matrix, full-color organic 2.4“, Febru ary - LG.Ph ilip s LCD laun ches AM OLED Bu sin ess. March - So n y in trod u ces Flash b ased MP3 p layers with OLED d isplay . 852x222 pixel, 1.8 mm thick display for March - Cano n says to start makin g OLED d isp lays n ext y ear . Ap ril - Samsu n g Licenses OLED Patents fro m Un iv ersal Disp lay . digital still and video cameras and other May - Ko d ak Licenses OLED Techn o lo g y to Fu ji Electric Ho ldings . May - CDT Achieves 1 0 0 ,000 Hour Blu e Poly mer Lifetime . portable imaging products; a contrast May - Samsu n g Electro n ics Develo p s Wo rld' s First 40 -inch a-Si-b ased OLED . ratio of more than 250:1, and a peak Ju n e - UDC ann o u n ces fu ndamental b reakth ro u gh in b lue PHOLEDs - New sky blue achieves over 15,000 hours of lifetime . July - Samsung SDI to invest over 850M$ in AMOLED produ ction. luminance of 200 cd/m 2. Au g u st - LG Electro n ics Laun ches Fu ll-Scale OLED Op eratio n s. September - To p p o ly d evelops a 7 " AMOLED d isp lay . Octo b er - Samsu n g SDI' s Org anic LED Disp lay Ship ments To p 3 0 Million un its . No v ember - CDT Prin ts a 1 4 " P-OLED d isp lay . www.spectrum.ieee.org/publicfeature/aug00/orgsf4.html No v ember - Ch in a's first OLED p ro ductio n lin e set u p . Dec ember - Pio n eer with d raws fro m AM-OLED mark et .

2 0 06 Janu ary - BenQ ann o unces a ca mer a and a p h o n e with larg e (2 .0 ") OLED screens . Janu ary - Ko d ak Bro adens its Particip atio n in OLED Techn o logy , end s OLED jo int v entu re with Sanyo . March - Un iv isio n to inv est $40 M in OLED lin e expansio n . March - Ep so n and CDT sh o ws wo rld's first p rint h ead u sing an OLED lig h tso u rce . Ap ril - Ko d ak Licenses OLED Techn o lo gy to Un iv ision Technolo gy . May - Pioneer Launches Mass Production at White OLED Plant. Ju n e - In d ia's Samtel to p ro duce OLED d isp lays . Au g u st - AUO relo cates OLED eng in eers, fo cuses o n LCD. September - first 'No k ia' phone with an OLED d isp lay . September - CDT se es rapid p ro g ress in Blu e and Red lifetime Octo b er - CMEL & CMO d evelo p 25" AMOLED TV p anel Octo b er - Samsu n g sh o wcases 1 7 " AMOLED www.kodak.com/US/en/corp/display/overview.jhtml 2 0 07 Janu ary - So ny showcase s 2 7 " and 11" OLED TVs at CES. Says mig h t start p roductio n at 20 08 . www.kodak.com/US/en/corp/display/activeDisplays.jhtm l

Flexibility DISPLAYS

Why bother with OLEDS? Flat panels: thin, light weight, low cost, novel applications Compare with competing LCDs: emissive, i.e. no backlighting Sales Pitch www.universaldisplay.com/concepts.php www.spectrum.ieee.org/publicfeature/aug00/orgsf1.html - Flexible - Large viewing angle Foldable Displays - Bright (10 5 Cd/m 2 peak in pulse operation) - Long Life? (30000 hours at 100 Cd/m 2) Passive-matrix 1.8 mm thick, 5x10 cm 128 x 64 pixel monochrome display; substrate: - Low voltage (3-8 V) polyethylene terephthalate (can bend into a - Good luminous efficiency (>20 lm/W) diameter less than a cm); operates at conventional video brightness of 100 cd/m 2. - Large colour range

Viewing Angle Brightness

www.kodak.com/US/en/corp/display/viewingAngle.jhtml

OLED LCD Image visible up to 160 degrees. Is that possible with LCDs? Not according to Brightness, contrast & colour: OLED better than LCD Kodak

http://www.kodak.com/US/en/corp/display/brightnessColor.jhtml

3 Some More Pretty Pictures Digital Cameras OLEDs in portable devices such as mobile phones, 2.2" OLED display with 512 x 218 pixels March 2003 (Kodak Announcement) digital video cameras, DVD players, and PDAs. Kodak three megapixel, LS633 Zoom digital camera. The LS633 is world's Car audio components first digital camera with OLED display. As there is no need for a www.kodak.com/US/en/corp/display/applications.jhtml manufactured by Pioneer and cellular phones backlight the LS633 should have good marketed by Motorola battery life. and Sanyo .

www.dpreview.com/news/0303/03030216kodakls633.asp

www.kodak.com/US/en/corp/display/intel.jhtm l

Automobile Applications Some Pr oducts in Mar ket

Sams ung YP-K5JQB 2 GB Audio Player with Bui... Nokia 6215i Phone (Verizon Wireless) Sony NW-S205F 2 GB Flash Sports Digital Mus ...

Automotive, Phillips Automotive, Siemens

Transparent substrate for displays on win d shield 512M B MP4/MP3 Playing Watc h with 1.5-Inc h O... Creative Zen V Plus 4 GB Portable Media Pla... Cowon iAudio6 4 GB M P3 Player (Black)

www.universaldisplay.com/toled.php 3DVis or Digital Display Sanyo Xacti VPC-HD1 5.1MP MPEG-4 High Defin... Iriver S10 Pos t Stamp Sized 2gb Mp3 Player ...

Two Flavours: S mall Molecules vs. Polymers Deposition Cluster Tool Multiple chamber OLED cluster Smal l Molecules currently d omina te PLEDs not yet have substantial market tool separated by Gate Va lves the OL ED d isplay market Ultra High Vacuum cryo pump based system The ma terials are inheren tly m ore PLED materials suffer from shorter Substrate transfer to and lifetimes, but improvement is occurring stable and robust than PL EDs from chambers within vacuum Devices are fluorescent, but movement Phosphorescent dopan ts for small towards phosphorescent devices also 5 micron alignment accuracy molecules make OL EDs more in UHV efficien t Multilayer deposit ion of Organ ic Spin coating limits the number of layers in layers Layers thermally evapoura ted in device vacuum; extensive opportuni ty for Low temperature evaporat ion device engineering (D ET AIL S) Film thickness < 500 A 0 PLEDs offer lower cost manufacturing Energy leve l compatibility The vacuum evapora tion process possibilities with ink jet printing , over large between layers for device limi ts the size o f the substra te substrates efficiency Suitable for Televisions and monitors Difficul t to upgrade for Television From Kurt Lesker and Moni tors Currently machines be ing Printing is yet to develop into a production tool. Currently, PLED manufacturing is developed for large glass sizes confined to monochrome displays, which do not require printing

4 Organic Thermal Ev apouration Sources All polymer device on p lastic substrates…

• Films only few tens of nanometers • Thickness con trol is critical • Temperature control within 0.1 to 1 oC • Design to enable minimal use of organic materials Back Back

Our Research on OLEDs Luminance-Voltage (L-V) characteristics

1.0 1.8 Current 1.0 n- C4 H9 Al ~ 25 0 nm UV emis sion PBPS • Development of full colour display prototype 1.5 Ca ~27 nm white emission 0.8 0.8 ) 2 PS-4 ~ 95 nm 1.2 0.6 PEDOT:PSS ~ 80 0.6 • Polysilane based OLED ITO 0.4 Si 0.9 Glass m 0.4 0.2 0.6 No Eintensity L rmlized EL 0.2 0.0 P L 0.3 Cu rrent (Cu mA/cm rrent 3 00 4 00 50 0 60 0 700 n- C4 H9

Organic Poly silanes N intensity zed ormali EL 0.0 0.0 Wavelen gth(nm)

0 2 4 6 8 10 12 14 1. π* -π Transit ion σ*-σ Trans ition

2. Lar ge S pectral Widt h Narr ow Spectral Width 1. 0 1.0 1.0 PS-4 P S-6 PS-8 3. Visible Em iss ion UV or NUV (difficult wit h p conjugated 0. 8 EL 0.8 0.8 polym ers as gap is < 3eV and 0. 6 0.6 0.6 0. 4 0.4 0.4 requir em ent of sm all ener gy loss before E L

0. 2 EL Normlized inten sity 0.2 EL Normlized inten sity 0.2 radiative deactiv ation) Inten sity Normalised PL EL PL 0. 0 0.0 0.0 P L

300 400 500 600 700 3 00 4 00 50 0 60 0 700 300 400 500 600 700 Wav eleng th (n m) Wavelen gth (nm) Wavelength (nm)

S i S i Si m m m

n- C4 H9 n- C6 H13 n- C8 H17

Voltage dependence of the UV and white emission Potential energy curves for new polymers (6-31g*)

6 M inolta spec trum at 1 3.7 5 V PBPS 10 10 PBPS 5 PS-4 PS-8 Minolta spectrum at 1.00 4 13.75, 14.74, 16.75, 17.75, 1.00 T,T ,T ,T,T ,T ,T 8 T6,T 7,T 8,T 9,T 10 ,T 11 ,T 12 8 6 7 8 9 10 11 12 19.75 V T T ,T 0.75 u.) (a. Intensity 3 T13 T14 ,T 15 13 14 15

0.75 6 5 2 6 S 1 4 S 0.50 1 23 1 400 5 00 600 700 8 00 Normalised T T 0.25 W avelength (nm) eV 5 5 4 T,T ,T T,T ,T 0.50 4 2 3 4 T 4 2 3 4 T 400 500 600 700 800 1 1 Intensit y (a.Intensit u.) y 2 2 0.25 S S 400 500 600 700 800 0 0 0 0 W avelength (nm) 2.0 2.5 3.0 3.5 2.0 2.5 3.0 3.5 Si-Si bond length (Å) Si-Si bond length (Å)

•Indian Patent Application No. 1532/DEL/2005

5 Organics Semiconductors: Beyond OLED & Lighting Future Outlook Molecular Electronics Active Enormous OTFT Matrix increase in device Solar Cells Displays density Print able RFID tags New Materials Impr ove m obi lity Rollable Modeling & Displays Simulation New Device Applications Structure drivers, Lith ogr ap hy-le ss OTFT communica- Low Cost, Large Sens ors tion, digital Samtel Center for Display Technologies Alternative Area, Flexible components Patterning substrate 1. S. S. K Iyer: Solar cells, OTFTs Techniques Integrat ed 2. Baquer Mazhari: Driver design, Solar Cells, OTFTs -Pri ntin g 3. Monica Katiyar: OLED, OTFTs Circuits 4. Y. N. Mohapatra: OLED, Lighting Device Integration CMOS 5. Satyendra Kumar: OLED, Solar Cells circuits – 6. A. R. Harish: RFID tags F lex ible Electro nics Can it RFID , Smart Cards replace Si in future?

Typical FET structure Pentacene FET (Top Contact)

Semiconductor

-5 - 5 Source + + + + + + Drain -VD -1.2x 10 - 20V 10 -1.0x 10 -5 Insulator Substrate: Glass, Plastic - 6 -8.0x 10 -6 10

Gate Source, Drain, Gate: -6.0x 10 -6 - 15V 10 - 7 -V -6 G Metal (Al, Au) -4.0x 10 -6 - 10V -2.0x 10 - 8 Substrate Insulator: PMMA, SiO - 5V 10 Dr ain Dr(A) ain Curren t 2 0.0 0V ( Cu Drain A) rrent - 9 -6 2.0x 10 10 0 -5 -10 -15 -20 15 10 5 0 -5 -10 -15 -20 -25 Dr ain Voltage (V) Pentacene Poly(3-hexylthiophene ) P3HT Ga te Volt age (V)

Mobility=0.22cm 2/V.s Threshold Voltage=-0.5V On/Off Ratio=10 4 Subthreshold Swing=3.5V/decade Pentacene Thickness=35 nm

Mobility Organic Solar Cells cathode Goal Higher efficiency (~10 %), rel iable a nd low cost / econom ical organic solar cells

Approach Understanding th e Physics Device Modelling Which metal cathode is better? Experimen ting wi th new M aterial New organic material from IIT Kanpur

Carbon Nanotubes, C 60 & PCBM New Device Structures Ca/Al electrode gives better (Contributed by Prof. S. S. K. Iyer) solar cell characteristics!

6 The Future of Organic Electronics Printable Electronics Piezoelectric crystal Ink Reservoir Goal Pulsed Signal Dev elop Printable Electronic Chamber Technologies Inkjet printing Nozzle Gravur e pr int ing Print Screen printing Inkjet printing for customised circuit Gravure printing for Approach high throughput Ink preparation Characterise printed devic es Des ign/fabric ate c ircuits Screen printing for low These are n ot our devices resolution & cost ckts RFID tags as prototypical product (Contributed by Prof. S. S. K. Iyer) for demonstration http://www.orgatronics.com/organic_elec tronics.html

Opportunities Ahead

1. Blue OLE D life tim e 2. Satur ated colours in display s, stable with v olt age 3. Mater ials and dev ic es with high effic iency in high curr ent regim e 4. Doping: p- doping deposition, search for n-doping m ater ial 5. TFT for active m atrix addr essing 6. Flex ible s ubstr ates and thin film encapsulat ion 7. Poly mer O LE DS, printing inks

8. Molec ular transist ors for high m obility 9. Conversion into numer ous possible applic ations