Plastic Electronics. Joaquim Puigdollers.

Transcription

1 Plastic Electronics Joaquim Puigdollers

2 Nobel Prize Chemistry 2000 Origins

3 Technological Interest

4 First products.. MONOCROMATIC PHILIPS

5 Today Future

6 Technological interest Low processing T (< 200ºC) Flexible Huge variety of polymers / organic molecules

7 Dyes Pigments: stables, small-molecule, visible optical absorption

8 Molecules with adjustable properties

9 Organic Devices Thin-film transistor (TFT) Thin-Film (Drain) (Source) (Gate) Light emitter diode (OLED) Solar cell Metal Electrodes Transparent electrode

10 Organic Solar Cells

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13 Organic material (or molecular material)?

14 Organic material (or molecular material)?

15 Polymer vs small molecule Complexity

16 Organic Solar Cells Two approach Polymer Small molecule Solution spin coating Thermal evaporation (sublimation) in high-vacuum

17 Basic structure Metal (Al, Ag) Organic semiconductor p / n layers Glass / Plastic ITO ITO: Indium Tin Oxide / Conductor and transparent Usually deposited by Sputtering

18 Inorganic Solar cell (Crystalline silicon)

19 Exciton Exciton: electron - hole pair (molecular or Frenkel exciton) quasi-free Frenkel CT F = - e 2 /4 π εε 0 r 2 Large binding energy (>> kt) due to the low dielectric constant Quasi-free charge carriers Frenkel exciton Charge-transfer (CT) exciton

20 HOMO LUMO levels LUMO Low Unocupied Molecular Orbital HOMO High Occupied Molecular Orbital LUMO similar to conduction band HOMO similar to valence band IP Ionization Potential [remove electron] EA Electron affinity [energy gained when an electron is added].

21 Photocurrent generation 1 Photon absorption and exciton generation 2 Exciton diffusion 3 Charge Transfer 4 Carrier collection anode cathode Donor Acceptor Donor Acceptor Semiconductor P-type Semiconductor N-type

22 Polymer solar cell Semiconductor Dissolution (different solvent) Spin coating Liquid distribution (spin-coating, or Dr Blade technique) Dr Blade technique

23 Small molecule solar cell Semiconductor (powder) Thermal evaporation in high vacuum

24 GloveBox

25 Our research activities at UPC on Organic Solar cells

26 Evolution Year 2002 Year 2006 Year 2011 MNT Micro and Nanotechnology group

27 Thermal evaporation MNT Micro and Nanotechnology group

28 p-type Metal evaporation n-type Organic evaporation intrinsic

29 Organic semiconductor purification by gradient thermal sublimation

30 AFM and STM microscope UHV. Small-molecule thermal deposition

31 Our solar cell p-i-n Absorbing layer Electrode N-type Electrode P-type Font electrode (Al) BCP Absorbing layer (DBP:C 70 ) MoO3 Transparent conductive layer (ITO) glass

32 Bilayer solar cell Al BCP 8nm C70 40nm DBP 10nm MoO3 3nm ITO Current Density (ma/cm 2 ) DBP Substrate temperature ,0 0,2 0,4 0,6 0,8 1,0 Voltage (V) Temp (C) PCE (%) Voc (V) J SC (ma/cm 2 ) FF

33 Facilities

34 Coevaporated solar cell Al BCP 8nm DBP : C70 (1:1) 40nm MoO3 3nm ITO T SUBS = 60 o C Coevaporated ~ 4% Current density (ma/cm 2 ) Jsc=11.2mA/cm 2 Voc=0.81V FF=43% η=3.93% -15-1,0-0,5 0,0 0,5 1,0 Voltage(V) Macko J.A., Lunt R.R., Osedach T.P., Brown P.R., Barr M.C., Gleason K.K., Bulovic V., Phys. Chem. Chem. Phys. 14, (2012) X. Xiao, J. D. Zimmerman, B. E. Lassiter, K. J. Bergemann, S. R. Forrest, Appl. Phys. Lett. 102, (2013)

35 Organic Thin-Film Transistors (OTFTs)

36 Working principle TFTs V Positive application GS Current D V DS Positive application S N-type Semiconductor _ G Dielectric

37 Working principle TFTs V GS Negative application Current V DS Negative application D S N-type Semiconductor G Dielectric

38 OTFTs OTFTs allows to determine field-effect mobility (µ) µ is an important parameter in organic solar cells OTFTs allow to optimize technological parameters P-type N-type N N N N N Cu N N N pentacene CuPc Carbazole Picene fullerene (C 60 ) DP-PTCDI F16CuPc PTCDI-C 13 TTF-TCNQ MNT Micro and Nanotechnology group

39 TFTs Structure Au Drain & Source electrodes Organic semiconductor Active layer SiO 2 Insulator c-si (Gate electrode)

40 Individual TFT characteristics Drain-Source Current (A) Drain-Source Current (A) 0-1x x x10-5 Pentacene PTCDI-C 13 V GS = -16, -32, -48, -64 V -4x Drain-Source Voltage (V) V DS = -10V Gate-Source Voltage (V) µ = 0.5 cm 2 /V s V T = 15.6 V µ = cm 2 /V s V T = 61.7V

41 OTFTs on alumnium foil W L Dielectric PMMA I DS (na) I DS (na) V GS =-20 V V GS =-30 V V GS =-40 V V DS (V) T subs = 30 ºC T subs = 60 ºC V DS (V) T subs = 90 ºC V GS = -40 V J. Puigdollers et al., presented at MRS Spring Meeting 2005 Au contacts (Source/Drain) Pentacene PMMA (gate dielectric) Al foil (gate electrode)

42 Complementary Inverter V DD G S V DD p-channel V IN V OUT V IN D D V OUT G S n-channel V SS V SS pentacene V OUT O PTCDI C 13 H 27 O V DD S p D n,p C 13 H 27 N O O N C 13 H 27 V SS S n V IN SiO 2 G n,p Substrate (c-si)

43 Voltage transfer characteristics V OUT Voltage Transfer Characteristics V IN V DD S G p-channel D V D OUT n-channel G S V SS Gain Gain dv OUT /dv IN V IN V in Difficulty to fabricate inverters with symmetrical characteristics

44 Complementary organic inverters (different W/L) V out n-6p 3n-4p 5n-2p V in V in Gain dv OUT /dv IN V DD V IN V OUT V SS Aspect ratio (W :W ): P N V DD 6:1 5:2 p-channel 4:3 3:4 2:5 V IN V OUT n-channel W L 1:6 V SS p-type: Pentacene n-type: PTCDI-C 13

45 Thank you