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1、平板显示技术 Flat Panel Display Technology,主动发光,主动发光 功耗小,轻、薄,Panasonic Matsushita （ 37-inch OLED TVs）,可弯曲,Samsung Demos Worlds First Bendable OLED Screen,Flexible AMOLED Display by ITRI,主要内容,1 有机半导体基础 2 OLED原理 3 OLED 器件设计 4 OLED显示面板的设计 5 OLED驱动原理 6 OLED 制作 7 OLED衰减机理 8 未来发展方向,OLED vs LCD,1 有机半导体基础,Transpo
2、rt in organic single crystals,Single crystals Holstein model Kenkre Model Silinsh and Capek model,Norbert Karls data (1980s) Hendrik Schons data (1999-2001)*,Refs: J.H. Schon et al. Phys. Rev. B63, Art 245201 (2001) Ch. 7; Silinsh and Capek,Organic semiconductors,Molecular orbitals Bonds and Bands,H
3、ydrocarbons,Orbital Description of probable electron density near a nucleus s Orbital Lowest energy orbital, spherical in shape p Orbital Dumbbell shaped Hybridization Mixing of orbitals Filling of orbitals Each molecular orbital can have a max. of 2 electrons Pauli principle (2 electrons must have
4、opposite spin) Aufbau principle Electrons always occupy orbitals of lowest energy first,Carbon,6 Electrons 1s2 2s2 2p2,One possibility: Hybridization (mixing of orbitals) 3 x sp2 orbitals + 1 pz orbital,Pz,Polyacenes: Number of p electrons: 4n +2,p electron overlap between adjacent carbon atoms: lea
5、ds to delocalization,Within a single molecule there is very good electronic overlap,Bonding,Covalent (Si) Electron sharing 2 or more electrons shared by 2 or more atoms Ionic (GaAs) Electron transfer Van der Waals (Bonding between covalent molecules) London forces (attraction between molecules with
6、no permanent dipole moment) Dipolar attraction (polar molecules) Hydrogen bonding (covalently bound hydrogen + negative dipole),Molecular Orbitals,Huckel MO Theory,(Isolated molecule),With overlap,2 electrons per orbital,Energy gap,C60,Materials,p-conjugated Molecules (oligomers) Transport p-p* over
7、lap,Crystal Structure - Anisotropy,Herringbone-Structure van-der-Waals (attraction) Pauli-Principle (repulsion) Layered Semiconductor,Anisotropy,Thiophenes Acenes,spar / sper 70 3,spar1 / spar2 1.5 1.5,Tetracene,Bandstructure of a-sexithiophene (a-6T),Anisotropy (Pentacene),3D Band Transport High T
8、( 400 K) : Crossover to Hopping,Effective, Electronic Bandwidth,Mass Renormalization / Shrinking of Bandwidth,Bandwidth, Mean Free Path, and Bandwidth,Pentacene,Self-Consistent Description,Electrical Field Dependence,Band-like Transport Phonon Scattering (acoust. Deformation- Potential Approximation
9、) Saturation Velocity (Non-Parabolicity),also for Naphthalene N. Karl et al. Phys. Rev. B 32, 1172 (1985),J. H. Schn et al. Phys. Rev. B 63, 245201 (2001),Electric Field Dependence,Low T : Phonon Scattering High T : Polaron Transport Intermediate T : Crossover !,Power law Band Transport (coherent) T
10、hermally Activated Hopping (incoherent) Universal Crossover (variety of molecular crystals) Localization of Charge Carrier due to Electron-Phonon Interaction !,Band-Like Transport Hopping Motion,J. H. Schn et al. Phys. Rev. Lett. 86, 384 (2001).,2 OLED发光原理,Recombination of hole and electron/ LED,OLE
11、D Device Physics 1. Charge injection Power Consumption - Organic-Metal Interfaces - Degradation - Intrinsic - Extrinsic,OLED operation,Electroluminescence Processes,1) Carrier Injection (balanced injection; Ne = Nh) 2) Carrier Transport (bipolar transport; me = mh) 3) Electron-hole recombination and
12、 exciton formation 4) Radiative and non-radiative recombination of excitons and energy transfer,Light output,Electrical Characteristics of polymer light emitting device,Diode Characeristics Rectification ratio ; 103 - 107,Power efficiency & drive voltage hconv = Popt / P elec = (hn / V) hext Light v
13、s current Iopt = hext X Ielec /e,Ex),Light Emitting Polymers,A novel light source,Light Emitting Polymers,Low energy consumption Usefull for large area lighting Simple to use technology Permits flexible lighting and displays A technology for the future,Light Emitting Polymers have a lot of advantage
14、s ,But how do Light Emitting Polymers,work,But how do Light Emitting Polymers,work?,But how do Light Emitting Polymers,work?,But how do Light Emitting Polymers,work?,But how do Light Emitting Polymers,work?,A typical device consists of 3 layers,Transparent Anode,Cathode (Metal),Light Emitting Polyme
15、r,+,+,+,+,If voltage is applied, positive charge carriers move into the anode, negative charge carriers into the cathode!,+,2-5 Volt,+,2-5 Volt,+,+,2-5 Volt,+,2-5 Volt,+,+,+,2-5 Volt,+,+,2-5 Volt,+,+,+,+,2-5 Volt,+,+,+,2-5 Volt,+,+,+,+,+,2-5 Volt,+,+,+,+,2-5 Volt,+,+,+,+,+,+,2-5 Volt,+,+,+,+,+,2-5 Volt,+,+,+,+,+,+,+,2-5 Volt,+,+,+,+,+,+,2-5 Volt,+,+,+,+,+,+,+,+,2-5 Volt,+,+,+,+,+,+,+,2-5 Volt,+,+,+,+,+,+,+,+,+,2-5 Volt,Then both types of charge carriers migrate into the polymer,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,
