Investigations of Naphthalimide and Pyrene Derivatives Based Organic Light Emitting Diodes

Abstract

Organic light-emitting devices (OLEDs) have been subject of intensive studies due to their great potential in display and lighting applications. The key point in OLEDs development for display and lighting applications is to find out materials emitting pure colours of red, green and blue with excellent emission efficiency and high stability. The efficiency of an OLED can be improved by balancing the transport of charge carriers in the device. Generally, this is done by including hole transporting and electron transporting materials in the OLED architecture. This thesis is focused on the study of electron transport materials for OLEDs based on novel naphthalimide and pyrene derivatives. This work improved the understanding on the physics of electron transport materials and the results of this study may be helpful for developing new devices and their applications. We observed that the naphthalimide derivatives have low-lying LUMO levels making them possess good electron-transporting and hole-blocking properties. The derivatives emitted in blue region with good chromaticity. In addition, they have high thermal stability and capable of forming good morphological films. Studies on the device properties of naphthalimide derivatives showed that they could be used as blue emitting electron transport materials. Also, the derivatives as host material in red OLEDs showed better performance than standard host material Alq3 in terms of both chromaticity and efficiency. Investigations on the OLEDs based on novel pyrene derivatives as green emitting electron transport materials showed better performance than Alq3. Temperature dependent electrical studies on the electron only devices showed that the pyrene derivatives have better electron mobilities than Alq3.