Perovskite Light Emitting Diodes An introduction to revolutionary display technology Perovskite Light Emitting Diodes, commonly referred to as Pe-LEDs, leverage a perovskite nanocrystal core to engender a luminous and efficient diode, holding the potential to bring about a paradigm shift in the realm of display technology. In recent times, Pe-LEDs have garnered substantial industrial interest due to their intrinsic capability to exhibit a diverse array of colors with exceptional fidelity, their operation at low voltage thresholds, and their straightforward structural composition. The prospective implications for enabling cost-effective, heightened-performance flat-panel displays as well as flexible display solutions remain notably profound. Perovskite Light Emitting Diodes: Materials and Devices presents a comprehensive and insightful overview of these diodes and their multifaceted applications. Commencing with an incisive exploration of the historical trajectory of this technology, alongside a delineation of its foundational materials and intricate device architectures, this compendium provides a gateway into both contemporaneous state-of-the-art deployments and the vanguard of ongoing research endeavors directed towards charting future advancements. Perovskite Light Emitting Diodes readers will also find: Stability analysis for different Pe-LED devices, a key aspect of creating physical displays Authorship by an established expert in organic electronics Detailed discussion of perovskite preparation methods including ultrasonic, solvent heat, thermal injection, and many more Perovskite Light Emitting Diodes is ideal for materials scientists, electrical engineers, solid state chemists, solid state physicists, inorganic chemists, and any researchers or engineers working with display technology.

Metal halide perovskites (MHPs) are recognized as promising semiconductor materials for a variety of optical and electrical device applications due to their cost-effective and outstanding optoelectronic properties. As one of the most significant applications, perovskite light-emitting diodes (PeLEDs) hold promise for future lighting and display technologies, attributed to their high photoluminescence quantum yield (PLQY), high color purity, and tunable emission color. The emission colors of PeLEDs can be tuned by mixing the halide anions, adjusting the size of perovskite nanocrystals, or changing the dimensionality of perovskites. However, in practice, all these different approaches have their own advantages and challenges. This thesis centres around the color tunability of perovskites, aiming to develop PeLEDs with different colors using different approaches. We first demonstrate red and near-infrared PeLEDs using a straightforward approach – in situ solution-processed perovskite quantum dots (PQDs). PQDs prepared from colloidal approaches are widely reported and used in LEDs. In contrast, PQDs prepared from the in situ approaches are hardly reported, although they have advantages for device applications. By employing aromatic ammonium iodide (1-naphthylmethyl ammonium iodide, NMAI) as an agent into perovskite precursor solutions, together with annealing temperature modulation, we obtain in situ grown PQDs delivering high external quantum efficiencies (EQEs) of up to 11.0% with tunable electroluminescence (EL) spectra (667 - 790 nm). Our in situ generated PQDs based on pure-halogen perovskites can be easily obtained through a simple deposition process and free of phase segregation, making them a more promising approach for tuning the emission colors of perovskite LEDs. We then move to blue PeLEDs using cesium-based mixed-Br/Cl perovskites. Although mixed halides are a straightforward strategy to tune the emission color, PeLEDs based on this approach suffer from poor color stability, which is attributed to surface defects at grain boundaries. Under the condition of optical excitations, light density over a certain value (a threshold), oxygen, and surface defects at perovskite grain boundaries are found to be key factors inducing photoluminescence (PL) spectral instability of CsPb(Br1?xClx)3 perovskites. Upon electrical bias, defects at grain boundaries provide undesirable halide migration channels, responsible for EL spectral instability issues. Through effective defect passivation, the PL spectral resistance to oxygen is enhanced; moreover, high-performance and color-stable blue PeLEDs are achieved, delivering a maximum luminance of 5351 cd m–2 and a peak EQE of 4.55% with a peak emission wavelength at 489 nm. These findings provide new insights into the color instability issue of mixed halide blue perovskites, against which we also demonstrate an effective strategy. We finally realize single-emissive-layer (EML) white PeLEDs by employing a mixed halide perovskite film as the EML. In spite of high-performance monochromatic blue, green, and red colors, the development of white PeLEDs, especially for single-EML ones, remains a very big challenge. By effective modulation of the halide salt precursors, we achieve single-EML white PeLEDs with Commission Internationale de L’Eclairage (CIE) coordinates of (0.33, 0.33), close to those (0.3128, 0.3290) of the CIE standard illuminant D65. This work not only provides a successful demonstration of a single-EML white PeLED, but also provides useful guidelines for the future development of highperformance single-EML white PeLEDs.

Metal halide perovskites have attracted significant attention for light-emitting applications, because of their excellent properties, such as high photoluminescence quantum yields (PLQYs), good charge mobility, narrow emission bandwidth, readily tunable emission spectra ranging from ultraviolet to near-infrared, and solution processability. Since the first room-temperature perovskite-based light-emitting diodes (PeLEDs) reported in 2014, tremendous efforts have been made to promote the efficiencies of PeLEDs, including theoretical simulation, materials design, and device engineering. To reach the ultimate goal of commercialization, PeLEDs with both high-efficiency and long-term operational stability are desired. Achieving high-quality perovskite emissive films is key towards this goal. Centering around the high-quality perovskite films, in this thesis, we demonstrate effective synthesis strategies for the deposition of high-quality perovskite films (including both three-dimensional and mixed-dimensional perovskites) and investigate the effects of ion migration in the perovskite films on the performance of PeLEDs. Due to the fast crystallization nature of perovskites and the low formation energy of defects, controlling the crystallization processes of these films has proved to be an effective approach for achieving high-quality perovskite films. For three-dimensional (3D) perovskite films, we have controlled the formation of these films through the assistance of molecules with the amino group. Herein, we have chosen an electron-transport molecule with two amino groups, 4,4’-diaminodiphenyl sulfone (DDS), to control the crystallization process of perovskite films (Paper 1). The resulting perovskite films consists of in-situ formed high quality perovskite nanocrystals embedded in the electron-transport molecular matrix, resulting in improved PLQYs and structural stability. PeLEDs based on these perovskite films have exhibited both high efficiency and long operational stability. In addition, we have investigated the formation of mixed-dimensional perovskite films. Efficient PeLEDs based on mixed-dimensional perovskite films were fabricated with tin dioxide (SnO2) as an electron transport layer (Paper 3). We also note that the deposition methods have a significant impact on the morphology and optical properties of prepared mixed-dimensional perovskite films (Paper 4). In addition, we provide an effective method to extend the deposition of mixed-dimensional perovskite films, replacing organic ammonium halides with amines in the perovskite precursor solutions to form organic spacer cations through the in-situ protonation process of amines (Paper 2). In spite of these efforts, the performance of PeLEDs is still far from the commercialization standard, partially limited by ion migration. In Paper 5, we discuss impacts of mobile ions in the perovskite films on the performance of PeLEDs. We find that a dynamic redistribution of mobile ions can change current density of a device, leading to EQE/hysteresis during forward and reverse voltage scan and enhanced EQE under constant driving voltages. In addition, we have found that excess mobile ions in the perovskite layer can aggravate the hysteresis and shorten the operational stability of PeLEDs. In this thesis, we also discuss the remaining key challenges in the PeLED field, including the achievement of high-performance blue, white, and lead-free PeLEDs, as well as possible strategies to address these challenges. We hope that our research findings provide insights into the basic science behind the perovskite materials, and broadly benefit other optoelectronic communities, such as perovskite solar cells, flexible electronics, and so on. Metall-halid-perovskiter har fått mycket uppmärksamhet för deras möjlighet att användas i ljusemitterande applikationer på grund utav utmärkta egenskaper så som högt fotoluminiscent kvantutbyte (PLQYs), god mobilitet, smalt emissionsband, lättjusterat emissionsspektra i intervallet ultraviolett till nära infrarött, samt för att de kan beredas med en lösningsbaserad process. Ända sedan de första perovskitbaserade ljusdioderna (PeLEDs) som verkande i rumstemperatur rapporterades 2014 har enormt arbete lagts ner på att öka effektiviteten hos PeLEDs, till exempel genom teoretiska simuleringar, materialdesign och teknisk utformning utav lysdioden. För att nå det slutgiltiga målet med kommersialisering behövs PeLEDs som har både hög effektivitet och driftstabilitet. Att uppnå högkvalitativa emitterande perovskitfilmer är nyckeln för att nå detta mål. I den här avhandlingen, vilken fokuserar på högkvalitativa perovskitfilmer, demonstrerar vi effektiva syntetiseringsstrategier för deponering utav högkvalitativa perovskitfilmer och undersöker effekterna jonmigration har på prestandan i perovskitfilmerna i PeLEDs. På grund utav den snabbkristalliserande naturen hos perovskitfilmer och den låga bildningsenergin för defekter så har kontroll utav kristallisationsprocessen av dessa filmer visat sig vara en effektiv väg för att uppnå högkvalitativa perovskitfilmer. När det gäller tredimensionella perovskitfilmer så har vi kontrollerat bildandet av dessa filmer genom assistans från molekyler med aminogrupper. Vi har valt en elektrontransporterande molekyl som har två aminogrupper, 4,4’- diaminodifenyl sulfon (DDS), för att kontrollera kristallisationsprocessen av perovskitfilmer (artikel 1). De beredda perovskitfilmerna bestod av insitu- bildade högkvalitativa perovskitnanokristaller inbäddade i en elektrontransporterande molekylär matris vilket resulterade i förbättrat fotoluminiscent-kvantutbyte och strukturell stabilitet. PeLEDs baserade på dessa perovskitfilmer har uppvisat både hög effektivitet och lång driftstabilitet. Därtill har vi undersökt bildandet av blanddimensionella perovskiter. Effektiva PeLEDs baserade på blanddimensionella perovskiter var tillverkade med tenndioxid (SnO2) som elektrontransportlager (artikel 3). Vi noterade även att val av deponeringsmetod hade signifikant effekt på IV morfologi och optiska egenskaper av de beredda blanddimensionella perovskitfilmerna (artikel 4). Därutöver tillhandahöll vi en effektiv metod för att deponera blanddimensionella perovskitfilmer genom att ersätta de vanligen använda organiska ammoniumhaliderna med aminer i prekursorlösningen för att bilda organiska distansierande katjonfilmer genom en in-situ-protoneringsprocess av aminer (artikel 2). Även om PeLEDs med högkvalitativa perovskitfilmer har visat förbättrad effektivitet och driftstabilitet så uppvisar lysdioderna fortfarande egenskaper som associeras med jonmigration. I artikel 5 diskuterar vi effekten av mobila joner i perovskitfilmer och hur de påverkar PeLEDs prestanda. Vi fann att den dynamiska omfördelningen av mobila joner i perovskitskiktet kan ändra det elektriska nettofältet i perovskitskiktet, modifiera laddningsbärarnas rekombination i perovskitskiktet och leda till ostadig strömdensitet. Dessutom har vi funnit att överskott av mobila joner i perovskitskiktet är en av de största anledningarna till den korta driftstabiliteten för PeLEDs. I denna avhandling diskuterar vi även kvarstående nyckelproblem i PeLED-fältet så som bedriften att uppnå högpresterande blå, vita och blyfria PeLEDs så väl som möjliga strategier att möta dessa utmaningar. Våra forskningsresultat ger insikter om den grundläggande vetenskapen bakom perovskitmaterialen vilka vi tror kommer vara till stort gagn för andra optoelektroniska fält, så som perovskitsolceller, flexibel elektronik och så vidare.

Advanced Nanomaterials for Solar Cells and Light Emitting Diodes discusses the importance of nanomaterials as the active layers in solar cells and light emitting diodes (LEDs), along with the progress of nanomaterials as the electron and hole transporting layers. Specifically, the book reviews the use of nano-morphology of polymers, small molecules, and the organic-inorganic perovskites as the active layers in solar cells and LEDs. The design, fabrication and properties of metal-oxide-based nano-structures as electron and hole transporting layers are also reviewed. In addition, the development of plasmonic nanomaterials for solar cells and LEDs is discussed. Each topic in this book includes an overview of the materials system from principles to process. The advantages, disadvantages and related methodologies are highlighted. The book includes applications based on materials and emphasize how to improve the performance of solar cells and LEDs by the materials design, with a focus on nanomaterials.

The book Organic Light Emitting Diode (OLED) Toward Smart Lighting and Displays Technologies, edited by Laxman Singh, Rituraj Dubey, and Prof. R. N. Rai, strives to address the multiple aspects of OLEDs and their applications in developing smart lightings and displays. OLEDs have been used in almost all kinds of digital displays like those of mobile phones, laptops, tablets, phablets, TVs, etc., due to their outstanding features, including superior color quality, low cost, wide viewing angle, easy fabrication, mercury-free manufacture, tenability, stretchability, flexibility, etc. Investigations related to the synthesis of new organic materials and fabrication techniques have inspired us to write this book, which will fulfil the desire and thirst of OLEDs-based researchers. Features • Nanolithographic techniques used and the challenges involved. • Printing technology for fabrication. • Designing of hybrid perovskites. • Stretchable and flexible materials used. • Metal–dielectric composites and efficiency of organic semiconductor via molecular doping for OLEDs applications. • Organic small molecule materials and display technologies involved. • New generation of organic materials with respect to photophysical approach. • Mixed valence π-conjugated coordination polymers used. • Electroluminescent polymer used. • Blue fluorescent and phosphorescent organic materials used. In comparison to other books available related to similar topics, this book aims at those audiences who are looking for a single source for a comprehensive understanding of strategies and their challenges with respect to material fabrication of OLEDs. This book covers the pace and productivity at a uniform level in each chapter with respect to the audiences, from doctoral student to postdoctoral researchers or from postdoctoral researchers to multidisciplinary field researchers with a background in physics, chemistry, materials science, and engineering, who are already working with organic materials and their applications.

This book focuses on basic fundamental and applied aspects of micro-LED, ranging from chip fabrication to transfer technology, panel integration, and various applications in fields ranging from optics to electronics to and biomedicine. The focus includes the most recent developments, including the uses in large large-area display, VR/AR display, and biomedical applications. The book is intended as a reference for advanced students and researchers with backgrounds in optoelectronics and display technology. Micro-LEDs are thin, light-emitting diodes, which have attracted considerable research interest in the last few years. They exhibit a set of exceptional properties and unique optical, electrical, and mechanical behaviors of fundamental interest, with the capability to support a range of important exciting applications that cannot be easily addressed with other technologies. The content is divided into two parts to make the book approachable to readers of various backgrounds and interests. The first provides a detailed description with fundamental materials and production approaches and assembly/manufacturing strategies designed to target readers who seek an understanding ofof essential materials and production approaches and assembly/manufacturing strategies designed to target readers who want to understand the foundational aspects. The second provides detailed, comprehensive coverage of the wide range of device applications that have been achieved. This second part targets readers who seek a detailed account of the various applications that are enabled by micro-LEDs.

Metal Halide Perovskites for Generation, Manipulation and Detection of Light covers the current state and future prospects of lead halide perovskite photonics and photon sources, both from an academic and industrial point-of-view. Advances in metal halide perovskite photon sources (lasers) based on thin films, microcrystals and nanocrystals are comprehensively reviewed, with leading experts contributing current advances in theory, fundamental concepts, fabrication techniques, experiments and other important research innovations. This book is suitable for graduate students, researchers, scientists and engineers in academia and R&D in industry working in the disciplines of materials science and engineering. - Includes comprehensive reviews from academic and industrial perspectives of current trends in the field of metal halide perovskite for photonics - Provides an up-to-date look at the most recent and upcoming applications in metal halide perovskite photonics, such as; photodetectors, lighting, lasing, nonlinear photonics and quantum technologies - Discusses future prospective trends and envisioned applications of metal halide perovskites, from near-UV to near-IR photonics

LED Lighting is a self-contained and introductory-level book featuring a blend of theory and applications that thoroughly covers this important interdisciplinary area. Building on the underlying fields of optics, photonics, and vision science, it comprises four parts. PART I is devoted to fundamentals. The behavior of light is described in terms of rays, waves, and photons. Each of these approaches is best suited to a particular set of applications. The properties of blackbody radiation, thermal light, and incandescent light are derived and explained. The essentials of semiconductor physics are set forth, including the operation of junctions and heterojunctions, quantum wells and quantum dots, and organic and perovskite semiconductors. PART II deals with the generation of light in semiconductors, and details the operation and properties of III-V semiconductor devices (MQWLEDs and μLEDs), quantum-dot devices (QLEDs & WOLEDs), organic semiconductor devices (OLEDs, SMOLEDs, PLEDs, & WOLEDs), and perovskite devices (PeLEDs, PPeLEDs, QPeLEDs, & PeWLEDs). PART III focuses on vision and the perception of color, as well as on colorimetry. It delineates radiometric and photometric quantities as well as efficacy and efficiency measures. It relays the significance of metrics often encountered in LED lighting, including the color rendering index (CRI), color temperature (CT), correlated color temperature (CCT), and chromaticity diagram. PART IV is devoted to LED lighting, focusing on its history and salutary features, and on how this modern form of illumination is deployed. It describes the principal components used in LED lighting, including white phosphor-conversion LEDs, chip-on-board (COB) devices, color-mixing LEDs, hybrid devices, LED filaments, retrofit LED lamps, LED luminaires, and OLED light panels. It concludes with a discussion of smart lighting and connected lighting. Each chapter contains highlighted equations, color-coded figures, practical examples, and reading lists.

Perovskite Photovoltaics and Optoelectronics Discover a one-of-a-kind treatment of perovskite photovoltaics In less than a decade, the photovoltaics of organic-inorganic halide perovskite materials has surpassed the efficiency of semiconductor compounds like CdTe and CIGS in solar cells. In Perovskite Photovoltaics and Optoelectronics: From Fundamentals to Advanced Applications, distinguished engineer Dr. Tsutomu Miyasaka delivers a comprehensive exploration of foundational and advanced topics regarding halide perovskites. It summarizes the latest information and discussion in the field, from fundamental theory and materials to critical device applications. With contributions by top scientists working in the perovskite community, the accomplished editor has compiled a resource of central importance for researchers working on perovskite related materials and devices. This edited volume includes coverage of new materials and their commercial and market potential in areas like perovskite solar cells, perovskite light-emitting diodes (LEDs), and perovskite-based photodetectors. It also includes: A thorough introduction to halide perovskite materials, their synthesis, and dimension control Comprehensive explorations of the photovoltaics of halide perovskites and their historical background Practical discussions of solid-state photophysics and carrier transfer mechanisms in halide perovskite semiconductors In-depth examinations of multi-cation anion-based high efficiency perovskite solar cells Perfect for materials scientists, crystallization physicists, surface chemists, and solid-state physicists, Perovskite Photovoltaics and Optoelectronics: From Fundamentals to Advanced Applications is also an indispensable resource for solid state chemists and device/electronics engineers.