Plastic Electronics Joaquim Puigdollers Joaquim.puigdollers@upc.edu
Nobel Prize Chemistry 2000 Origins
Technological Interest
First products.. MONOCROMATIC PHILIPS
Today Future
Technological interest Low processing T (< 200ºC) Flexible Huge variety of polymers / organic molecules
Dyes Pigments: stables, small-molecule, visible optical absorption
Molecules with adjustable properties
Organic Devices Thin-film transistor (TFT) Thin-Film (Drain) (Source) (Gate) Light emitter diode (OLED) Solar cell Metal Electrodes Transparent electrode
Organic Solar Cells
Organic material (or molecular material)?
Organic material (or molecular material)? http://peumans-pc.stanford.edu/teaching/ee322-wtr-06
Polymer vs small molecule Complexity
Organic Solar Cells Two approach Polymer Small molecule Solution spin coating Thermal evaporation (sublimation) in high-vacuum
Basic structure Metal (Al, Ag) Organic semiconductor p / n layers Glass / Plastic ITO ITO: Indium Tin Oxide / Conductor and transparent Usually deposited by Sputtering
Inorganic Solar cell (Crystalline silicon) http://britneyspears.ac/physics/basics/basics.htm
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
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].
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
Polymer solar cell Semiconductor Dissolution (different solvent) Spin coating Liquid distribution (spin-coating, or Dr Blade technique) Dr Blade technique
Small molecule solar cell Semiconductor (powder) Thermal evaporation in high vacuum
GloveBox
Our research activities at UPC on Organic Solar cells
Evolution Year 2002 Year 2006 Year 2011 MNT Micro and Nanotechnology group
Thermal evaporation MNT Micro and Nanotechnology group
p-type Metal evaporation n-type Organic evaporation intrinsic
Organic semiconductor purification by gradient thermal sublimation
AFM and STM microscope UHV. Small-molecule thermal deposition
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
Bilayer solar cell Al BCP 8nm C70 40nm DBP 10nm MoO3 3nm ITO Current Density (ma/cm 2 ) 0-1 -2-3 -4-5 DBP Substrate temperature 30 60 90 120-6 0,0 0,2 0,4 0,6 0,8 1,0 Voltage (V) Temp (C) PCE (%) Voc (V) J SC (ma/cm 2 ) 30 1.92 0.79-5.29 0.46 60 2.48 0.89-4.79 0.58 90 1.96 0.85-4.53 0.51 120 1.98 0.83-4.56 0.52 FF
Facilities
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 ) 15 10 5 0-5 -10 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, 14548 14553 (2012) X. Xiao, J. D. Zimmerman, B. E. Lassiter, K. J. Bergemann, S. R. Forrest, Appl. Phys. Lett. 102, 073302 (2013)
Organic Thin-Film Transistors (OTFTs)
Working principle TFTs V Positive application GS Current D V DS Positive application S N-type Semiconductor _ G Dielectric
Working principle TFTs V GS Negative application Current V DS Negative application D S N-type Semiconductor G Dielectric
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
TFTs Structure Au Drain & Source electrodes Organic semiconductor Active layer SiO 2 Insulator c-si (Gate electrode)
Individual TFT characteristics Drain-Source Current (A) 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 Drain-Source Current (A) 0-1x10-5 -2x10-5 -3x10-5 Pentacene PTCDI-C 13 V GS = -16, -32, -48, -64 V -4x10-5 -40-30 -20-10 0 Drain-Source Voltage (V) V DS = -10V -80-60 -40-20 0 20 Gate-Source Voltage (V) µ = 0.5 cm 2 /V s V T = 15.6 V µ = 0.036 cm 2 /V s V T = 61.7V
OTFTs on alumnium foil W L Dielectric PMMA I DS (na) 60 40 20 0-20 -40 I DS (na) 0-2 -4-6 -8 V GS =-20 V V GS =-30 V V GS =-40 V -40-30 -20-10 0 V DS (V) T subs = 30 ºC T subs = 60 ºC -60-40 -30-20 -10 0 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)
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)
Voltage transfer characteristics V OUT 20 15 10 5 Voltage Transfer Characteristics V IN V DD S G p-channel D V D OUT n-channel G S V SS Gain 4 3 2 1 Gain dv OUT /dv IN 0-30 -20-10 0 10 20 30 40 50 V IN -20 0 20 40 0 V in Difficulty to fabricate inverters with symmetrical characteristics
Complementary organic inverters (different W/L) V out 20 15 10 5 0 1n-6p 3n-4p 5n-2p 0 5 10 15 20 0 2 4 6 8 1012 0 V in V in 35 30 25 20 15 10 5 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
Thank you