Computational Molecular Dynamics Study of Organic light Emitting Diodes

Abstract

Organic Light Emitting Diodes (OLEDs) have been the subject of an intense research effort aimed at improvement their performance resulting in the emer gence as a key component in the lighting and display market. Indeed, in dis play field, OLEDs have registered 23.2% of the market share. Increasing de mand for global OLEDs display market impels continued development and improvement to OLEDs performance and sustainability. This means higher efficiency, cheaper production and brighter materials with longer lifetimes are required. This makes the research about OLEDs important in both exper imental and theoretical. In the context of OLEDs, Thermally Activated delayed fluorescent (TADF) has emerged as a highly appealing mechanism for delivering highly-efficient third generation OLEDs. First generation OLEDs were based on the fluo rescent molecules, which could not harvest non-radiative triplet states and therefore only achieve low internal quantum efficiency (IQE < 25%). The sec ond generation OLEDs has overcome this using phosphorescence through intersystem crossing making it possible to achieve 100% IQE using heavy metals. But these are often rare and expensive. In this thesis, a theoretical study of molecules exhibiting TADF via excited state intramolecular proton transfer (ESIPT) is performed using quantum chemistry, quantum dynamics and molecular dynamics to understand the fundamental mechanism of triplet harvesting. Chapter 1 introduces the basic definitions and principal knowledge about OLEDs, TADF and ESIPT. Chap ter 2 talked about he background theory and theoretical methods have been used in study, especially density functional theory and molecular dynam ics. Chapter 3 discussed the ESIPT dynamics in OLEDs, resulted how the triplet harvesting plays the important role in OLEDs. Chapter 4 illustrates the examination of quantum tunneling and the impact of polarity on energy barriers. In Chapter 5, the role of excitation generation is also discussed.