Temperature Characterization of Colloidal Quantum Dot Light Emitting Diodes

Abstract

Colloidal quantum dot light emitting diodes reveal to be promising candidates for the next generation of display technologies. Their brighter emissions, greater color purity, and higher efficiency make them highly desirable in consumer electronics. As such, research into the performance and stability of these novel LEDs are crucial for their operation in displays. These investigations are ongoing, with focused efforts on improving the operating stability through different quantum dot materials and passivation methods. However, less attention is paid in confidently understanding the fundamental relationships between current, voltage, and luminance by which these devices operate. These electrical characteristics reveal insights into the operation of these devices and the behavior of charge carriers. Additionally, temperature-dependent electrical measurements can showcase different behavior at different temperatures and deviations from the expected performance at set temperatures. Temperature dependent processes are revealed and from such, a better understanding of how the device operates is gained. In this thesis, an investigation into the temperature-dependent electrical characteristics of quantum dot light emitting diodes was conducted by measuring the current-voltage-luminance, JVL, relationships at various cryogenic temperatures. These temperatures ranged from 78K, liquid nitrogen boiling point, to 293K, room temperature. This investigation revealed the temperature dependent nature and origin of turn-on voltage, current, EQE, EQE roll-off, and hysteresis.