Preface

The manufacture of light emitting diodes (LEDs) has opened many opportunities in science and technology by providing work for novel smart display gadgets. The triumph of emerg‐ ing micro- and nanosized LEDs has become lengthened with advanced hi-tech improve‐ ments in technologies. Ultimately, the LED can be broken down into three major categories: (i) traditional inorganic LEDs, (ii) organic LEDs (small molecule OLEDs, polymer LEDs, pas‐ sive matrix OLEDs, and active matrix OLEDs), and (iii) high brightness LEDs. With the in‐ creased demand for OLED-based touchscreens, electronics manufacturers are increasingly turning to UV LEDs because of their many benefits in bonding applications for OLED flat panel manufacturing. The benefits to manufacturers include high productivity, environmen‐ tal safety and friendliness, and a reliable solution to how these products are cured. LEDs are low cost, fascinating, and important to humankind. Capitalizing on the latest applications of LEDs has proffered innovative technological advancements, which have been rapidly imple‐ mented for groundbreaking research, especially in the subnanoscale, which involves physi‐ cal and chemical properties of the lighting process.

For more than a decade, semiconductor technology has been elevated to greater heights. The result is in the form of nifty semiconductor electronic devices. Furthermore, commercially available LEDs and OLEDs deliver enhanced illumination with low power consumption and have longer lifetimes too. Undoubtedly, these innovations have survived the impact of the different sizes, shapes, and even the circuit design to which an LED can be affixed. Also, the production of LEDs encompasses the following: flexible thin film LEDs and OLEDs, col‐ or capability, low power consumption, brighter images, wide viewing angles, fast response times, low cost, extended lifespan, UV sensitivity, restriction of hazardous substances manu‐ facturing compatibility (lead free), etc., in comparison with their traditional counterparts. There are a number of concrete motives for switching to LED bulbs, due to their durability, chemical stability, extended lifetime, cost-effectiveness, etc. In addition, LEDs are not over‐ sensitive to temperature or humidity, making them ideal for active indoor and outdoor lighting. Unlike *compact fluorescent* lamps (CFLs), which contain a minor quantity of mercu‐ ry, LEDs are not manufactured with any precarious material making them safe both around the home (even if broken) and when they are disposed of.

Globally, there is a faster growth into an additional defensible way of living environment, the LEDs and OLEDs captivating over the illumination space by replacing with CFL bulbs. For some reasons, LEDs still do not dominate the commercial market, which is still controlled by the first generation of LED light bulbs that have narrow light beams. and that the flea market prices were at first besides costs more. However, all these issues are being overcome with the help of recent advancements in LED technology. Clusters of LED precut chips are being as‐ sembled during the fabrication of second-generation LED lights. These are known as surfacemounted diodes. The modern generation of LED lighting uses chip on board technology, as well as new filament technology that contributes to the outcome of incandescence. The present day sees the latest fabrication techniques on LEDs and OLEDs providing scientific developments at the frontline of optical sciences with good international prospects. As a re‐ sult, the aforesaid technological advancements in LEDs and OLEDs may perhaps be desired for these applications. The capability to imitate modern LED devices from microscale to nanoscale is of pivotal importance to the advancement in micro- and nanotechnologies. This book forms the basis for a better fundamental understanding of the capabilities and limita‐ tions of LEDs, and also may suggest better, cheaper, or alternative lighting technologies.

The broad spectrum of this book provides exhaustive coverage of selected advanced topics in LEDs and OLEDs by highly experienced authors. Also, research scientists from dissimilar areas are very often prolifically employed in the field of LEDs and OLEDs all over the global network. This book describes the advanced knowledge of frontline subjects in LED and OL‐ ED materials and their applications. The chapters of the book have been contributed by emi‐ nent scholars active in recent research and development in materials science, and are ideal for researchers and students to gain an understanding of the basic ideas that are imperative to the pertinent areas of research. It is our expectation that you, the readers, will find this book of immense help in your research.

The book consists of seven chapters dealing with LEDs and their phototoxic-cum-bacterici‐ dal effect of blue LED irradiation, the history of LEDs and OLEDs with necessary examples, DC network indoor and outdoor LED lighting, white organic LEDs with thermally activated delayed fluorescence emitters, tetradentate cyclometalated platinum (II) complex-based effi‐ cient organic LEDs, the impact of the use of large LED lighting loads in low-voltage net‐ works, highly efficient OLEDs using thermally activated delayed fluorescent materials, and AlGaN deep ultraviolet LEDs.

I would like to thank all the contributors of the chapters for their tremendous efforts in cre‐ ating outstanding work. Last but not least, I would like to express my sincere gratitude to Ms. Danijela Sakic, publishing process manager, for effective communication and assistance during the preparation of this book.

> **Jagannathan Thirumalai** SASTRA Deemed University Tanjavur, India

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: The Impression of Light-Emitting**

Amid the supreme contemporary machineries in lamps and lighting devices, Light-emitting diodes (LEDs) have an enormous amount of novel applications day by day, and flattering ever more prevalent and manageable to the societal benign. Basically, the LED is connected to direct current which emits light in the visible region of spectrum. While experimenting with silicon carbide (crystal detectors) and a cat's whisker, the first discovery of electroluminescence phenomenon using light emitting diode was noticed back at the beginning of the twentieth century (1907), by a British radio engineer H J Round and the assistant to Guglielmo Marconi [1, 2]. In 1927, the phenomenon of electroluminescence in the diodes used in radio sets was studied by a Russian radio researcher Oleg Vladimirovich Losev. Also a credit toward his research, he has published a paper named Luminous carborundum [silicon carbide] detector and detection with crystals [3]. At room (298 K), low (77 K) temperature and even in other semiconductor alloys, the infrared emission was observed by employing the simple diode structures with indium phosphide (InP), silicon-germanium (SiGe), gallium arsenide (GaAs), and gallium antimonide (GaSb) alloys by Rubin Braunstein in 1955 [4]. Years later in the fall 1961, the first infrared LED was invented and patented by Robert Biard and Gary Pittman [5–7]. In 1962, the first visible red LED was invented by Nick Holonyack, using gallium arsenide phosphide (GaAsP) as a substrate for the diode [8]. By employing gallium arsenide phosphide in the diode, the first yellow LED was invented by M George Craford in 1972 [9]. In 1968, the Monsanto Company was the leading group of institution has made a mass-production of visible red LEDs as indicators using gallium arsenide phosphide (GaAsP). Nevertheless, it was not in anticipation of the 1970s that LEDs befitted popular as

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.79375

**Diodes in Space-Age Advancements and Its Effect of**

**Light-Emitting Diodes in Space-Age Advancements** 

**Introductory Chapter: The Impression of** 

**and Its Effect of Blue LED Irradiation**

**Blue LED Irradiation**

Jagannathan Thirumalai

Additional information is available at the end of the chapter

**1. A succinct evidence of light-emitting diode**

Jagannathan ThirumalaiAdditional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.79375

#### **Introductory Chapter: The Impression of Light-Emitting Diodes in Space-Age Advancements and Its Effect of Blue LED Irradiation Introductory Chapter: The Impression of Light-Emitting Diodes in Space-Age Advancements and Its Effect of Blue LED Irradiation**

DOI: 10.5772/intechopen.79375

Jagannathan Thirumalai

mounted diodes. The modern generation of LED lighting uses chip on board technology, as well as new filament technology that contributes to the outcome of incandescence. The present day sees the latest fabrication techniques on LEDs and OLEDs providing scientific developments at the frontline of optical sciences with good international prospects. As a re‐ sult, the aforesaid technological advancements in LEDs and OLEDs may perhaps be desired for these applications. The capability to imitate modern LED devices from microscale to nanoscale is of pivotal importance to the advancement in micro- and nanotechnologies. This book forms the basis for a better fundamental understanding of the capabilities and limita‐ tions of LEDs, and also may suggest better, cheaper, or alternative lighting technologies.

The broad spectrum of this book provides exhaustive coverage of selected advanced topics in LEDs and OLEDs by highly experienced authors. Also, research scientists from dissimilar areas are very often prolifically employed in the field of LEDs and OLEDs all over the global network. This book describes the advanced knowledge of frontline subjects in LED and OL‐ ED materials and their applications. The chapters of the book have been contributed by emi‐ nent scholars active in recent research and development in materials science, and are ideal for researchers and students to gain an understanding of the basic ideas that are imperative to the pertinent areas of research. It is our expectation that you, the readers, will find this

The book consists of seven chapters dealing with LEDs and their phototoxic-cum-bacterici‐ dal effect of blue LED irradiation, the history of LEDs and OLEDs with necessary examples, DC network indoor and outdoor LED lighting, white organic LEDs with thermally activated delayed fluorescence emitters, tetradentate cyclometalated platinum (II) complex-based effi‐ cient organic LEDs, the impact of the use of large LED lighting loads in low-voltage net‐ works, highly efficient OLEDs using thermally activated delayed fluorescent materials, and

I would like to thank all the contributors of the chapters for their tremendous efforts in cre‐ ating outstanding work. Last but not least, I would like to express my sincere gratitude to Ms. Danijela Sakic, publishing process manager, for effective communication and assistance

> **Jagannathan Thirumalai** SASTRA Deemed University

> > Tanjavur, India

book of immense help in your research.

AlGaN deep ultraviolet LEDs.

VIII Preface

during the preparation of this book.

Additional information is available at the end of the chapter Jagannathan ThirumalaiAdditional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.79375
