Halbleiter Prof. Yong Lei Prof. Thomas Hannappel

Transcription

1 Halbleiter Prof. Yong Lei Prof. Thomas Hannappel

2 Organic Semiconductors & Organic Electronics

3 Organic semiconductors Small-molecular materials Rubrene Pentacene Polymers PEDOT:PSS P3HT π-conjugated organic molecules

4 The Nobel Prize in Chemistry 2000 The Nobel Prize in Chemistry 2000 was awarded jointly to Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa ("for the discovery and development of conductive polymers ) Page 4

5 The discovery of conductive polymer J. Chem. Soc. Chem. Comm (1977) Page 5

6 Conductive polymer: a surprising discovery In1967, a visiting coworker of Shirakawa tried to make polyacetylene via conditions identical to reported method. Rather than having polymer powder as expected, pieces of a polymer film were produced instead. Upon reviewing the reaction conditions, Shirakawa found that the film formation was a result of the fact that the catalyst concentration used had been 1000 times higher than intended. Hideki Shirakawa Shirakawa explained the mistake: I might have missed the m for mmol in my experimental instructions, or the student might have misread it. MacDiarmid gives a quite different account: this occurred because of a misunderstanding between the Japanese language and that of a foreign student who had just joined his group. H. Shirakawa, in T. Frängsmyr, Ed., Les Prix Nobel. The Nobel Prizes 2000, Nobel Foundation, Stockholm, Page 6

7 Polyacetylene: insulator to semiconductor Polyacetylene Iodine-doped Polyacetylene Page 7

8 The first result was obtained in 1963! Polypyrrole A series of three papers by D.E. Weiss were lost and then Diaz was credited with the discovery of polypyrrole as a conducting polymer. D.E. Weiss, Aust. J. of Chem. 663, (1963) A.F. Diaz, J. Chem. Soc. Chem. Comm (1979) Page 8

9 P-type organic semiconductors J. Mater. Chem., 2010, 20, Page 9

10 N-type organic semiconductors Page 10

11 Typical semiconducting polymers Page 11

12 Energy diagram of organic semiconductors

13 P-type and N-type organic semiconductors P-type [N-type] does not reflect the ability of a material to transport holes [or electrons]; it rather indicates the ease with which holes being injected into HOMO [or electrons being injected into LUMO] of material from electrodes. The energy of HOMO [or LUMO] determines (approximately) the ionization potential (electron affinity) of the material.

14 P-type and N-type organic semiconductors Pentacene Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDI)

15 HOMO/LUMO levels and bandgap of organic semiconductors HOMO/LUMO levels and bandgap are controlled by type of conjugated system, electron donating/electron withdrawing group (substituent) Conjugated system: The HOMO increases in energy with increasing conjugation length. The LUMO decreases in energy with increasing conjugation length. The band gap (Eg) is decreased with increasing conjugation length. Electron donating/electron withdrawing groups (substituents): Electron donating groups increase the energy levels. Electron withdrawing groups (e.g. fluorine) decrease the energy levels. Pentacene: P-type Perfluoropentacene: N-type

16 Effect of substituents on HOMO/LUMO of organic semiconductors Chem. Phys. Lett. 2017, 684,

17 Effect of substituent on HOMO/LUMO of organic semiconductors

18 Ambipolar organic semiconductors Chem. Phys. Lett. 2017, 684,

19 Silicon vs. Pentacene (single crystal) Silicon Pentacene Melting point (K) Intrinsic 300K [Ω m] Electron 300K [cm 2 / (V s)] Hole 300K [cm 2 / (V s)]

20 Single crystal of organic semiconductors Silicon Rubrene

21 What makes organic materials conductive? Mater. Horiz. 2017,4,

22 Advantages and disadvantages of organic semiconductors for electronics Advantages: 1. Unlimited options of material design, structures and morphologies 2. Band gap engineering 3. Light, flexible, inexpensive 4. Easy and cheap processing (ink-jet printing, spin coating) Disadvantages: 1. Poor crystallinity: highly localized charge carriers 2. Stability and Lifetime: possible degradation under environmental influences 3. Low mobility: low speed of devices 4. Organic/Inorganic Interfaces

23 Organic electronics: semiconducting, conducting, and light emitting properties

24 Organic electronics Organic photovoltaic cell OPV (Ching W Tang, Kodak) Organic field-effect transistor OFET (H Koezuka, Mitsubishi) Organic light-emitting diode OLED (Ching W Tang, Kodak) OLED OFET OPV

25 Organic light-emitting diodes (OLEDs)

26 Organic electroluminescence Electroluminescence was observed from single crystals of anthracene. The Journal of Chemical Physics, 38, 2042 (1963) Phys. Rev. Lett. 14, 229 (1965). 5 mm thick anthracene crystal! EL quantum efficiency ~ 1-5%! High driving voltage! Anthracene Page 26

27 Organic electroluminescent diodes Appl. Phys. Lett. 1987, 51, 913. Ching W. Tang Configuration of EL cell and molecular structures Ekctroluminescence spectrum of ITO/diamine/ Alq3/Mg:Ag.

28 Device structure of OLEDs

29 Multilayer structure of OLED Electrons injected from cathode Holes injected from anode Transport and radiative recombination of electron-hole pairs at emission layer.

30 Highly efficient and stable tandem OLEDs J. Mater. Chem. C, 2015, 3,

31 Working principle of OLED Electrons injected from cathode Holes injected from anode Transport and radiative recombination of electron-hole pairs at the emission layer. Chem. Soc. Rev., 2010, 39,

32 Working principle of OLED Addition of layers at electrodes/active emission layer - facilitate charge and exciton confinement & charge injection and transport Multi-layer architecture improves efficiency comparing to a single-film emitting layer device

33 The color of OLEDs Organic electroluminescent materials Sumitomo Chemical announced 60-Color Polymer OLED Lighting in 2012.

34 Device fabrication of OLED (layer-by-layer) Small molecules Polymers Small molecule semiconductor and/or electrodes can be deposited by PVD Conducting polymer layer is deposited from solutions (spin coating, drop casting, dip coating ) Annealing may be required after solution process Cathode can be deposited as layer or pattern (using shadow mask)

35 OLED fabrication: Evaporation

36 OLED fabrication: Printing

37 High Efficient Fiber OLEDs for Wearable Electronics Nano Lett., DOI: /acs.nanolett.7b04204, Publication Date (Web): December 6, 2017

38 AMOLED: Active Matrix OLED Active matrix: addressing of pixels. OLED with a back panel of thin-film transistors (TFTs) is AMOLED. TFT is a device operating as a switch an element (pixel) on or off - manage pixels in AMOLED, is necessary for a high quality display, particularly in large size display.

39 Sixth-Generation Flexible AMOLED

40 Organic field-effect transistors (OFETs)

41 Field-effect transistors (FETs) FET: conductivity of the path between two contacts: source and drain, is controlled by a voltage applied on the gate. The source of water pressure accumulated electrons at the negative electrode of applied voltage from Drain to Source The drain of water electron deficiency at the positive electrode of applied voltage from Drain to Source. Control of water flow Gate voltage controls the width of n-channel, which in turn controls electron flow in n-channel from source to drain.

42 Field-effect transistors (FETs) Classical FET FET in which (typically single-crystalline) semiconductor serves as substrate logic circuits, computer chips, Thin Film Transistor - TFT FET in which all active components are deposited onto an insulating substrate switches in Displays, Radio frequency identification (RFID) tags Organic field-effect transistors (OFETs) are thin film transistors.

43 Device configuration of organic thin film transistor (OTFT) All active layers are deposited as thin film onto a substrate: thin film transistor (TFT) Source, drain and gate electrodes typically made of Au, Ag, Al, ITO, PEDOT:PSS, etc. Dielectric typically metal oxides (Al 2 O 3, HfO 2, SiO 2 ) or organic insulators (PMMA, SAMs)

44 Working principle of OTFT Applying a gate voltage V g leads to accumulation of charge carriers (holes) in organic semiconductor at the interface to the dielectric. When drain voltage V D = 0 V, holes are uniformly distributed over the whole organic semiconductor at the interface to the dielectric.

45 Working principle of OTFT Applying a drain voltage at the drain electrode V D < 0 V leads to hole flow between source and drain (= drain current I D ) When V D V G - V th, charge carriers are nearly uniformly distributed over the whole channel Linear increase of the drain current I D with V D. (linear regime)

46 Working principle of OTFT When V D V G - V th, hole distribution is not uniform anymore. Increase of drain current I D is not linear anymore with V D (called transition regime) Page 46

47 Working principle of OTFT When V D V G - V th, hole distribution is highly asymmetric over the channel. Drain current I D saturates and does not increase anymore with V D (called saturation regime) Page 47

48 OTFT characteristics As V G and V D can be varied, two different current-voltage characteristics can be measured: Measuring I D as a function of V D, with fixed V G : output characteristic Measuring I D as a function of V G, with fixed V D : transfer characteristic

49 OTFT Device Geometries (a) Bottom-gate (inverted) staggered OTFT. (b) Bottom-gate (inverted) coplanar OTFT. (c) Top-gate staggered OTFT. (d) Top-gate coplanar OTFT. Chem. Soc. Rev., 2010, 39,

50 Potential applications of OTFT Gas sensors Photodetectors Pressure sensors J. Mater. Chem. C, 2014, 2, ; Chem. Soc. Rev., 2013, 42, ; Nature Communications 2013, 4,1859.

51 Organic complementary circuits Pentacene F16CuPc Schematic, photograph, and transfer characteristics of an organic complementary inverter based on a pentacene p-channel TFT and a F16CuPc n-channel TFT. Chem. Soc. Rev., 2010, 39, Page 51

52 Organic complementary inverter on banknotes as security feature A 5-Euro note with arrays of organic complementary inverter fabricated directly on the surface of the banknote as security feature. Adv. Mater. 2011, 23,

53 References

54 Organic photovoltaics

55 References Page 55

56 Jan Hendrik Schön had published 15 first-authorized papers about organic semiconductors on Science and Nature in 2000 and 2001!!! 1. Ambipolar pentacene field-effect transistors and inverters, JH Schön, S Berg, C Kloc, B Batlogg, Science 287 (5455), (2000). 2. Self-assembled monolayer organic field-effect transistors, JH Schön, H Meng, Z Bao, Nature 413 (6857), (2001). 3. An organic solid state injection laser, JH Schön, C Kloc, A Dodabalapur, B Batlogg, Science 289 (5479), (2000) 4. Superconductivity at 52 K in hole-doped C60, JH Schön, C Kloc, B Batlogg, Nature 408 (6812), (2000) 5. High-temperature superconductivity in lattice-expanded C60, JH Schön, C Kloc, B Batlogg, Science 293 (5539), (2001). 6. Efficient organic photovoltaic diodes based on doped pentacene, JH Schön, C Kloc, E Bucher, B Batlogg, Nature 403 (6768), (2000). 7. Superconductivity in molecular crystals induced by charge injection, JH Schön, C Kloc, B Batlogg, Nature 406 (6797), (2000) 8. A superconducting field-effect switch, JH Schön, C Kloc, RC Haddon, B Batlogg, Science 288 (5466), (2000). 9. Gate-induced superconductivity in a solution-processed organic polymer film, JH Schön, A Dodabalapur, Z Bao, C Kloc, O Schenker, B Batlogg, Nature 410 (6825), (2001). 10.A light-emitting field-effect transistor, JH Schön, A Dodabalapur, C Kloc, B Batlogg Science 290 (5493), (2000). 11.Fractional quantum hall effect in organic molecular semiconductors, JH Schön, C Kloc, B Batlogg, Science 288 (5475), (2000) 12.Field-effect modulation of the conductance of single molecules, JH Schön, H Meng, Z Bao Science 294 (5549), (2001). 13.Superconductivity in single crystals of the fullerene C70, JH Schön, C Kloc, T Siegrist, M Steigerwald, C Svensson, B Batlogg, Nature 413 (6858), (2001) 14.Field-induced superconductivity in a spin-ladder cuprate, JH Schön, M Dorget, FC Beuran, XZ Xu, E Arushanov, M Lagues, et al. Science 293 (5539), (2001) 15.Josephson junctions with tunable weak links, JH Schön, C Kloc, HY Hwang, B Batlogg, Science 292 (5515), (2001)

57 2000: Schön s huge fraud An organic solid state injection laser Schön, Kloc, Dodabalapur, SCIENCE 289, 5479, , 2000 (retracted) Jan Hendrik Schön In 2002, Jan Hendrik Schön was fired after his work was found to contain fraud data. It was the first known case of fraud at Bell Labs : compact organic laser pumped by microchip laser 2006 : diode-pumped organic laser 2008 : 1st LED-pumped organic laser (Samuel) 2010 : organic polariton laser (Forrest) 2011 : first start-up company on organic solid-state lasers (Visolas)

58 Organic semiconductors lasers

59 Thank you!