AMOLED Displays with In-Pixel Photodetector

The focus of this chapter is to consider additional functionalities beyond the regular display function of an active matrix organic light-emitting diode (AMOLED) display. We will discuss how to improve the resolution of the array with OLED lithography pushing to AR/VR standards. Also, the chapter will give an insight into pixel design and layout with a strong focus on high resolution, enabling open areas in pixels for additional functionalities. An example of such additional functionalities would be to include a photodetector in pixel, requiring the need to include in-panel TFT readout at the peripherals of the full-display sensor array for applications such as finger and palmprint sensing

Investigations of Charge-Transport and Photophysical Properties of Wide-Gap Organic Semiconducting Materials and Their Device Applications

近年來有機發光元件在平面顯示器與照明應用上漸受矚目。然而為了實現高品質的全彩顯示器與照明元件，高效率三原色發光元件是不可或缺的，其中紅光與綠光之有機發光元件逐漸成熟，至於藍光元件則尚待改善，因此寬能隙有機半導體的相關研究便十分重要。影響發光元件效率的各種材料特性中，載子傳輸特性與光物理特性對於元件特性有很大的影響。而對於有機半導體材料而言，分子結構的微小差異可能會對材料特性造成巨大的影響。故在本論文中，透過研究不同系列之寬能隙有機分子之光物理與載子傳輸特性，藉由分子構造的探討，希望找出能提升有機寬能隙發光元件效率的分子設計。論文中先研究在寡聚物芴化合物(oligofluorene)的九號碳上，不同取代基對載子傳輸特性的影響。接著探討主鏈長度對於茚芴(indenofluorene)化合物之光物理以及載子傳輸特性的影響。本論文次一主題研究了在C3與C6接上不同取代基之咔唑化合物(carbazole)的光物理以及載子傳輸特性，並探討了此載子傳輸特性對元件效率的影響。接著本論文探討了不同架接位置對於寡聚物咔唑化合物的光物理以及載子傳輸特性影響，並發現某些特定寡聚物咔唑化合物具有雙極性載子傳輸特性。本論文最後藉由具有雙極性載子傳輸特性之芴衍生物，實現了藍光與可調色彩之有機發光場效電晶體。Organic light emitting devices (OLEDs) have attracted wide interest for display and lighting applications in the past decade. Thus high-efficiency OLEDs with three primary color, red, green, and blue, are important for high quality display and lighting applications. Highly efficient red and green OLEDs have become readily available nowadays. However, efficient and stable blue emitters are still highly desired. Therefore the researches of wide-gap organic semiconductors for further developments are very important. mong the characteristics of organic materials, charge-transport and photophysical properties have significant effects on the device performances. In organic semiconductors, slight modification of the molecule configuration could alter the material properties significantly. Therefore, the relation between the molecule configuration and the corresponding charge-transport and photophysical properties is of high interest. n the thesis, we first investigate a series of oligofluorenes with different side-chain substituents on C9 to depict the effects of the side-chain substituents on the charge-transport properties. Subsequently, the charge-transport and photophysical properties of a series of indenofluorenes with different main-chain length are investigated. In addition, we investigate the photophysical and charge-transport properties of a series of triphenylsilyl/trityl-substituted carbazoles. The obtained information is used to explain the corresponding device performance. Further, the photophysical and charge-transport properties of a series of oligocarbazoles with different linking topologies are investigated. Ambipolar charge-transport properties are observed for the first time in some pure oligocarbazole systems. In the end, two fluorene-based materials are employed as the active layers in organic light-emitting transistors (OLETs) to demonstrate blue and color-controllable OLETs.Chapter 1 Introduction.1 Operation mechanisms of various organic optoelectronics and their material requirements - 1 -.2 Motivation of investigating wide-gap organic semiconductors - 4 -.3 Thesis Organization - 6 -hapter 2 Experimental and Analysis Methods.1 Introduction - 10 -.2 Material preparation and characterization - 11 -.3 Photophysical characterizations. - 12 -.4 Characterization of charge-transport properties by time-of-flight (TOF) methods. - 12 -.4.1 Introduction - 12 -.4.2 Principles of the time-of-flight mobility measurement - 15 -.4.3 Preparation of TOF samples - 19 -.4.4 Models of charge-transport in organic semiconductors - 20 -.4.4.1 Introduction - 20 -.4.4.2 Bässler formalism - 23 -.4.4.3 Marcus electron transfer theory - 25 -eference - 27 -hapter 3 Charge-Transport Properties of p-Tolyl Substituted Oligo(fluorene)s.1 Introduction - 35 -.2 Material properties - 38 -.3 Results and discussions - 39 -.3.1 TOF Results in T3 amorphous films - 39 -.3.2 TOF Results in 4D amorphous films - 40 -.3.3 Discussions - 42 -.4 Summary - 44 -eference - 45 -hapter 4 Photophysical and Charge-Transport Properties of p-Tolyl Substituted Indenofluorenes.1 Introduction - 62 -.2 Results and discussions - 64 -.2.1 Material properties of oligo(indenofluorene)s - 64 -.2.2 Photophysical properties of oligo(indenofluorene)s - 64 -.2.3 Charge-transport properties of oligo(indenofluorene)s - 67 -.2.3.1 InF3 - 67 -.2.3.2 InF4 - 67 -.2.3.3 InF5 - 68 -.2.3.4 Discussions - 70 -eference - 72 -hapter 5 Photophysical and Charge-Transport Properties of Carbazole-based Materials.1 Introduction - 86 -.2 Triphenylsilyl/Trityl-substituted Carbazoles. - 88 -.2.1 Introduction - 88 -.2.2 Material and photophysical properties - 90 -.2.3 Charge-transport properties - 91 -.2.4 Discussions - 93 -.3 Carbazole-based dimers and trimers with different linking topologies - 95 -.3.1 Introduction - 95 -.3.2 Photophysical properties of the oligocarbazoles - 97 -.3.2.1 39BCz - 97 -.3.2.2 39TCz - 97 -.3.2.3 33BCz - 98 -.3.2.4 33TCz - 98 -.3.2.5 27BCz - 99 -.3.2.6 29BCzA - 99 -.3.2.7 29BCz - 100 -.3.2.8 29TCz - 100 -.3.2.9 Comparison of photophysical properties - 101 -.3.3 Charge-transport properties of the oligocarbazoles - 104 -.3.3.1 39BCz - 104 -.3.3.2 39TCz - 104 -.3.3.3 33BCz - 105 -.3.3.4 33TCz - 105 -.3.3.5 27BCz - 105 -.3.3.6 29BCzA - 106 -.3.3.7 29BCz - 106 -.3.3.8 29TCz - 107 -.3.3.9 Comparison of charge-transport properties. - 107 -.3.4 Summary - 109 -eference - 110 -hapter 6 Applications of Wide-Gap Charge-Transport and Emitting Materials in Organic Light Emitting Transistors.1 Introduction - 149 -.2 Experimental methods - 151 -.3 Blue light emitting transistors - 153 -.4 Color-controllable light-emitting transistors - 157 -.5 Summary - 162 -eferences - 163 -hapter 7 Summar

Efficient OLEDs Based on Slot-Die-Coated Multicomponent Emissive Layer

The optimization of multicomponent emissive layer (EML) deposition by slot-die coating for organic light-emitting diodes (OLEDs) is presented. In the investigated EMLs, the yellow-green iridium complex (Ir) was doped in two types of host: a commonly used mixture of poly(N-vinylcarbazole) (PVK) with oxadiazole derivative (PBD) or PVK with thermally activated delayed fluorescence-assisted dopant (10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-10H-spiro[acridine-9,9′-fluorene], SpiroAC-TRZ). In this article, OLEDs with EML prepared in air by slot-die coating, facilitating industrial manufacturing, are confronted with those with spin-coated EML in nitrogen. OLEDs based on PVK:PBD + 2 wt.% Ir-dopant exhibit comparable performance: ~13 cd A−1, regardless of the used method. The highest current efficiency (21 cd A−1) is shown by OLEDs based on spin-coated PVK with 25 wt.% SpiroAC-TRZ and 2 wt.% Ir-dopant. It is three times higher than the efficiency of OLEDs with slot-die-coated EML in air. The performance reduction, connected with the adverse oxygen effect on the energy transfer from TADF to emitter molecules, is minimized by the rapid EML annealing in a nitrogen atmosphere. This post-treatment causes more than a doubling of the OLED efficiency, from 7 cd A−1 to over 15 cd A−1. Such an approach may be easily implemented in other printing techniques and result in a yield enhancement

Overlapping-Gate Organic Light-Emitting Transistors

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A light-emitting transistor in which two gates, separated by an insulator, partially overlap in the center of the device is proposed. By accumulating charge carriers in dedicated transport layers, each gate independently controls charge injection into the emissive layer sandwiched between the transport layers. This structure combines the advantages of pinned light emission in the center of the channel, gapless charge transport into the recombination zone, and controlled balance of electron and hole concentration at the edges of the emissive layer for any chosen current density. High-performance devices with overlapping gates are demonstrated: Using a red fluorescent emitter, high external quantum efficiency (5.7%) is conserved up to the highest luminance (2190 cd m−2). A comprehensive optoelectronic device model is proposed that verifies the measured characteristics and confirms that efficiency is highest with balanced charge transport. This device topology opens perspectives in the development of bright thin film light sources driven at high current densities.status: publishe

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

Many methods have been proposed to increase the efficiency of organic electroluminescent materials applied as an emissive layer in organic light emitting diodes (OLEDs). Herein, we demonstrate enhancement of electroluminescence efficiency and operational stability solution processed OLEDs by employing thermally activated delayed fluorescence (TADF) molecules as assistant dopants in host-guest systems. The TADF assistant dopant (SpiroAC–TRZ) is used to facilitate efficient energy transfer from host material poly(N–vinylcarbazole) (PVK) to a phosphorescent Ir(III) emitter. We present the analysis of energy transfer and charge trapping—two main processes playing a crucial role in light generation in host–guest structure OLEDs. The investigation of photo-, electro- and thermoluminescence for the double-dopant layer revealed that assistant dopant does not only harvest and transfer the electrically generated excitons to phosphorescent emitter molecules but also creates exciplexes. The triplet states of formed PVK:SpiroAC–TRZ exciplexes are involved in the transport process of charge carriers and promote long–range exciton energy transfer to the emitter, improving the efficiency of electroluminescence in a single emissive layer OLED, resulting in devices with luminance exceeding 18 000 cd/m2 with a luminous efficiency of 23 cd/A and external quantum efficiency (EQE) of 7.4%

On the Extraction of Charge Carrier Mobility in High-Mobility Organic Transistors

Transistor parameter extraction by the conventional transconductance method can lead to a mobility overestimate. Organic transistors undergoing major contact resistance experience a significant drop in mobility upon mild annealing. Before annealing, strong field-dependent contact resistance yields nonlinear transfer curves with locally high transconductances, resulting in a mobility overestimate. After annealing, a contact resistance below 200 Ω cm is achieved, which is stable over a wide V G range.status: publishe

Transglutaminase Cross-Linked Gelatin-Alginate-Antibacterial Hydrogel as the Drug Delivery-Coatings for Implant-Related Infections

Implant-related infection may be catastrophic and result in poor functional outcome, chronic osteomyelitis, implant failure or even sepsis and death. Based on a transglutaminase (TGase) cross-linked/antibiotics-encapsulated gelatin-alginate hydrogel, the main aim of this study is to establish an effective antibiotic slow-release system. The second aim is to evaluate the efficacy of a hydrogel-encapsulated antibiotic-containing titanium pin in preventing implant-related infections in a rat model. The prepared gelatin/alginate/gentamicin or vancomycin hydrogel was covalently cross-linked with transglutaminase (TGase). Its drug release profile and cytotoxicity were determined and the Wistar rat animal model was performed to validate its efficacy by radiographic examination, Micro-CT (computed tomography) evaluation and histo-morphological analysis at 12 weeks after surgery. When gelatin and alginate were thoroughly mixed with TGase, both 0.5% and 1.0% TGase can effectively cross link the hydrogel; the release of antibiotic is slowed down with higher degree of TGase concentration (from 20 min to more than 120 h). In the animal study, antibiotic-impregnated hydrogel is effective in alleviating the implant-related infections. Relative to that of a positive control group, the experimental group (vancomycin treatment group) showed significant higher bone volume, more intact bony structure with only mild inflammatory cell infiltration. This newly designed hydrogel can effectively deliver antibiotics to reduce bacterial colonization and biofilm formation on the implant surface. The remaining challenges will be to confer different potent antibacterial medications with good biocompatibility and fulfill the safety, practical and economic criteria for future clinical translation

Transglutaminase Cross-Linked Gelatin-Alginate-Antibacterial Hydrogel as the Drug Delivery-Coatings for Implant-Related Infections

Implant-related infection may be catastrophic and result in poor functional outcome, chronic osteomyelitis, implant failure or even sepsis and death. Based on a transglutaminase (TGase) cross-linked/antibiotics-encapsulated gelatin-alginate hydrogel, the main aim of this study is to establish an effective antibiotic slow-release system. The second aim is to evaluate the efficacy of a hydrogel-encapsulated antibiotic-containing titanium pin in preventing implant-related infections in a rat model. The prepared gelatin/alginate/gentamicin or vancomycin hydrogel was covalently cross-linked with transglutaminase (TGase). Its drug release profile and cytotoxicity were determined and the Wistar rat animal model was performed to validate its efficacy by radiographic examination, Micro-CT (computed tomography) evaluation and histo-morphological analysis at 12 weeks after surgery. When gelatin and alginate were thoroughly mixed with TGase, both 0.5% and 1.0% TGase can effectively cross link the hydrogel; the release of antibiotic is slowed down with higher degree of TGase concentration (from 20 min to more than 120 h). In the animal study, antibiotic-impregnated hydrogel is effective in alleviating the implant-related infections. Relative to that of a positive control group, the experimental group (vancomycin treatment group) showed significant higher bone volume, more intact bony structure with only mild inflammatory cell infiltration. This newly designed hydrogel can effectively deliver antibiotics to reduce bacterial colonization and biofilm formation on the implant surface. The remaining challenges will be to confer different potent antibacterial medications with good biocompatibility and fulfill the safety, practical and economic criteria for future clinical translation