Handbook of Aggregation-Induced Emission, Volume 3

Emerging Applications

Youhong Tang, Ben Zhong Tang, Youhong Tang, Ben Zhong Tang

• Publisher: Wiley
• Year: 2022
• Print ISBN:
  9781119642992
• eBook ISBN:
  9781119643067
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

The third volume of the ultimate reference on the science and applications of aggregation-induced emission 

The Handbook of Aggregation-Induced Emission explores foundational and advanced topics in aggregation-induced emission, as well as cutting-edge developments in the field, celebrating twenty years of progress and achievement in this important and interdisciplinary field. The three volumes combine to offer readers a comprehensive and insightful interpretation accessible to both new and experienced researchers working on aggregation-induced emission. 

In Volume 3: Emerging Applications, the editors address the applications of AIEgens in several fields, including bio-imaging, fluorescent molecular switches, electrochromic materials, regenerative medicine, detection of organic volatile contaminants, hydrogels, and organogels. Topics covered include:  

• AIE-active emitters and their applications in OLEDs, and circularly polarized luminescence of aggregation-induced emission materials 
• AIE polymer films for optical sensing and energy harvesting, aggregation-induced electrochemiluminescence, and mechanoluminescence materials with aggregation-induced emission 
• Dynamic super-resolution fluorescence imaging based on photoswitchable fluorescent spiropyran 
• Visualization of polymer microstructures 
• Self-assembly of micelle and vesicles 
• New strategies for biosensing and cell imaging 

Perfect for academic researchers working on aggregation-induced emission, this set of volumes is also ideal for professionals and students in the fields of photophysics, photochemistry, materials science, optoelectronic materials, synthetic organic chemistry, macromolecular chemistry, polymer science, and biological sciences. 

1
AIE‐active Emitters and Their Applications in OLEDs

Qiang Wei^1,2, Jiasen Zhang^1,2,3,, and Ziyi Ge^1,2

¹ Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo, China

² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China

³ Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci‐Tech University, Hangzhou, China

1.1 Introduction

Organic light‐emitting diode (OLED) can convert electricity into light within organic emissive layers (EMLs) under external voltage. Since the pioneering work of Tang and VanSlyke [1], this technology has seen a rapid progress in the past three decades and has already realized commercial application in various electronic appliances, such as smartwatches, mobile phones, cameras, and so on [2–4], owing to its significant advantages, such as low cost, low‐driving voltage, light weightiness, and fast response [5–10]. Furthermore, this technology was regarded as the future major displaying and lighting technology [11–13].

Typical OLED devices consist of two electrodes, i.e., anode and cathode, and several organic layers sandwich between these two electrodes. Within OLED devices, electrons and holes are injected from cathode and anode, respectively, and pass through several organic layers, such as hole injection layer (HIL), electron injection layer (HIL), hole transport layer (HTL), and electron transport layer (ETL), and finally recombine in the EML with a small part of photons passing through transparent electrode to emit light (Figure 1.1) [12]. As for OLEDs, the organic EML plays a vital role in determining the devices’ performances, especially for color, luminance, and efficiency. OLED devices’ color was judged according to Commission Internationale de l’Eclairage (CIE) coordinates [15, 16]. Internal quantum efficiency (IQE) and external quantum efficiency (EQE), defined as the numerical ratio of photons generated within or out of the devices to electron‐hole pairs injected, are usually applied to evaluate the OLEDs’ capability of electron–photon conversion [17, 18]. Compared with IQE, the parameter EQE are more reliable, which is determined by the photoluminescence quantum efficiency (PLQY) of emitters in the solid films, balanced factor of electrons and holes, and out‐coupling efficiency. Because photons are not only emitted out of but also generated within the EMLs, the emitters’ structures, aggregated state, and properties can strongly determine OLED manufacturing process and performance [19].

Figure 1.1 The OLED devices and aggregated‐state lightening. (a) The construction of OLED emitter, (b) OLED’s working mechanism, (c) aggregation‐caused quenching, and (d) aggregation‐induced emissive phenomenon.

Source: Reproduced with permission from John Wiley and Sons [3, 13, 14].

Under electrical excitation, emitter can produce singlet excitons and triplet excitons in the ratio of 1 : 3 according to spin statistics; there are several types of emitters with different photophysical mechanisms in terms of utilizing the electrons. Traditional fluorescent emitters can take advantage of singlet excitons to produce fluorescence, with maximum IQE of 25% and maximum EQE of merely 5% provided that out‐coupling efficiency is 20%. In order to improve OLEDs’ efficiency, triplet excitons were further taken into consideration and various mechanisms were put forward. According to photophysical mechanisms of utilizing triplet‐harvesting, OLEDs with high exciton utilizing efficiency (EUE) can be classified into different groups. Phosphorescent emitters can reach 100% IQE with phosphorescent emission through the mechanism of spin–orbit coupling [20]. Thermally activated delayed fluorescent (TADF) emitters can also reach the maximum IQE of 100% by upconverting the lowest triplet to the lowest singlet via reverse‐intersystem crossing (RISC) under external energy [21–27]. The emitters with hybridized local and charge transfer (HLCT) state also share 100% IQE with fluorescent emission, through upconverting triplet charge transferring (CT) state to singlet local excited (LE) state in higher excited states [28–31]. In addition, some other new mechanisms were reported in OLEDs with high EQE, such as triplet–triplet annihilation (TTA) [32], triplet exciton‐polaron annihilation [33], neutral π ‐radical [34], and singlet fission [35].

Furthermore, as a kind of solid‐state lightening technologies [5], not only molecular structures but also aggregated state of emitters can significantly influence the light‐emitting behaviors. One of the frustrating problems associated with most conventional luminogens is aggregation‐caused quenching (ACQ) effects, which mean that the fluorescence of the emitters was dim or totally quenched in the solid state, in spite of their strong emission in solution, and it may significantly reduce the device’s efficiency. The ACQ phenomenon is usually caused by the emitter’s large conjugated plane, which tends to experience serious intermolecular interactions, such as π–π stacking. Various methods, including chemical modifications or physical doping processes were proposed to reduce the molecule aggregation and the ACQ phenomena, but only limited achievement has been made and also some other side effects were brought about. Fortunately, some luminogenic molecules feature a distinctive photophysical process of AIE [14]. Opposite to the ACQ phenomena, the lumino...

Table of contents

• Cover
• Table of Contents
• Title Page
• Copyright Page
• Dedication Page
• List of Contributors
• Preface to Handbook of Aggregation‐Induced Emission
• Preface to Volume 3: Applications
• 1 AIE‐active Emitters and Their Applications in OLEDs
• 2 Circularly Polarized Luminescence of Aggregation‐induced Emission Materials
• 3 AIE Polymer Films for Optical Sensing and Energy Harvesting
• 4 Aggregation‐induced Electrochemiluminescence
• 5 Mechanoluminescence Materials with Aggregation‐Induced Emission
• 6 Dynamic Super‐resolution Fluorescence Imaging Based on Photo‐switchable Fluorescent Spiropyran
• 7 Visualization of Polymer Microstructures
• 8 Self‐assembly of Aggregation‐induced Emission Molecules into Micelles and Vesicles with Advantageous Applications
• 9 Vortex Fluidics‐mediated Fluorescent Hydrogels with Aggregation‐induced Emission Characteristics
• 10 Design and Preparation of Stimuli‐responsive AIE Fluorescent Polymers‐based Probes for Cells Imaging
• 11 AIE
• 12 AIE-based Systems for Imaging and Image-guided Killing of Pathogens
• 13 AIEgen‐based Trackers for Cancer Research and Regenerative Medicine
• 14 AIE‐active Fluorescence Probes for Enzymes and Their Applications in Disease Theranostics
• 15 AIE Nanoprobes for NIR‐II Fluorescence In Vivo Functional Bioimaging
• 16 In Vivo Phototheranostics Application of AIEgen‐based Probes
• 17 Red‐emissive AIEgens Based on Tetraphenylethylene for Biological Applications
• 18 Smart Luminogens for the Detection of Organic Volatile Contaminants
• 19 Bulky Hydrophobic Counterions for Suppressing Aggregation‐caused Quenching of Ionic Dyes in Fluorescent Nanoparticles
• 20 Fluorescent Silver Staining Based on a Fluorogenic Ag+ Probe with Aggregation‐induced Emission Properties
• Index
• End User License Agreement