Contents

#### **Preface XI**


Preface

The world has seen a huge research development in the field of organic light emitting devices (OLEDs) (commonly known as the organic light emitting diodes) in the last two decades. This is because such devices exhibit a number of extra technical features in flat panel displays that conventional display devices do not. These advantageous features include high brightness and contrast, high luminous efficiency, fast response time, wide viewing angle, low power consumption, flexible structures, light weight and low cost manufacturing chemical technology. Furthermore, the advancement in developing the concept of rendering white light from OLEDs for domestic, commercial and street lighting has boosted the research activity in this field. The organic white light emitting devices (OWLEDs), traditionally known as the white organic light emitting devices (WOLEDs) show promise to have a major share in future ambient lighting due to their favourable properties mentioned above. In addition, as similar chemical technology can be used to fabricate both, WOLEDs and organic solar cells (OSCs), it opens new ways in lighting design such as light ceilings or luminous objects of almost any shape. A common flexible substrate can be used to fabricate WOLEDs on one side facing a room and OSCs on the other side facing the sun. The device thus fabricated can generate power in the day time and light a room/house at night. This

book covers developments on OLEDs, WOLEDs and briefly on OSCs as well.

fabrication and the performance of the resulting devices are discussed.

Several other books have recently appeared on OLEDs and related topics but the field is too active to cover up to date development in one volume for very long. Although the existing resources can provide valuable fundamental information on organic electroluminescence, this book provides the state-of-the-art advancement in the field of organic electroluminescence contributed by many established experts in the field.

This volume contains eight chapters contributed by many expert researchers worldwide. Chapter 1 introduces the mechanism of light extraction from the excited singlet and triplet exciton states. The concept of capturing the triplet exciton emission has been fully understood only recently through the invention of the new timedependent exciton-spin-orbit-photon interaction operator and its role is very critical in fabricating WOLEDs. Chapter 2 deals with the development of field emission organic light emitting diodes (FEOLEDs) which have a better balance (equality) in the number of injected electrons and holes and hence have higher luminous efficiency. Both
