Dependence of the current and power efficiencies of organic light-emitting diode on the thickness of the constituent organic layers

The dependence of the current and power efficiencies of bi-layer organic light-emitting diodes (OLEDs) on the thickness of the constituent organic layers is reported. The thickness of the electron and hole transport layers was simultaneously varied to determine the optimal configuration for power efficiency. It was verified that the inclusion of a suitable electrode buffer layer reduced the effective energy barrier against carrier injection, thus improved the injection efficiency. An optimal thickness for the electrode buffer layer was also identified and explained.

I. Introduction

Though liquid-crystal display is presently the dominant flat-panel display technology because of its portability, low power consumption, and mature manufacturing practice, organic light-emitting diode (OLED) has attracted great attention [1] [2] [3] since the demonstration of efficient electro-luminescence (EL) from a bi-layer device by Tang et al. [4]. In addition to sharing many of the favorable attributes with liquid-crystals, OLEDs are attractive as alternative display components because of their relative merits of being self-emitting, having large intrinsic viewing angle and fast switching speed. However, because of their relatively short history of development, much remains to be explored in terms of their basic device physics and design, manufacturing techniques, stability, and integration with such active electronic elements as transistors [5] [6]–[7] [8].