Highly Efficient OLEDs

Chapter 9The Role of Vibronic Coupling for Intersystem Crossing and Reverse Intersystem Crossing Rates in TADF Molecules

Thomas J. Penfold and Jamie Gibson

Newcastle University, School of Chemistry, NE1 7RU Newcastle upon Tyne, UK

9.1 Introduction

Since the first report of electroluminescence (EL) in poly(para‐phenylenevinylene) [1], there has been an enormous amount of effort dedicated to the development of organic light‐emitting diodes (OLEDs). However, early attempts to implement OLEDs based solely upon organic materials were restricted by an intrinsically low EL efficiency. This arose from the limit imposed by the statistics of the spin states formed under electrical excitation. Indeed, following electrical excitation only 25% of the excitons ...