Hsing-Chung Lee

Organic light-emitting diodes with a bipolar transport layer

A structure based on a bipolar transport/emitting layer is proposed and implemented for making organic light-emitting diodes. Compared to the conventional heterojunction organic light-emitting diodes, more than a factor of six improvement in device reliability (a projected operating lifetime of 70 000 h) is achieved in the structure. The significant improvement in device lifetime is attributed to the elimination of the heterointerface present in the conventional devices which greatly affects the device reliability.

A low cost, high performance optical interconnect

Optobus is a ten channel parallel bi-directional datalink based on multimode fiber ribbons. The design represents a series of tradeoffs between cost and performance to produce a low cost interconnect solution with a minimum of 1.5 Gbit/s of aggregate throughput.

Carrier transport mechanisms in organic electroluminescent devices

The current-voltage relationships in organic electroluminescent devices are derived for the following two cases: (1) double-carrier injection trap-charge limited (TCL) regime, and (2) TCL conduction with internal photodetrapping. Several experimental observations are explained based on our equations. Location of the recombination zone is predicted. A numerical model is also developed to simulate the TCL conduction. Current-voltage characteristics, band and charge profiles are obtained to elucidate the conduction mechanism in the organic electroluminescent devices with large trap densities.

From research to manufacture—The evolution of MOCVD

The article provides an overview of the manufacturing capabilities of metalorganic chemical vapor deposition (MOCVD) technology and describes its application to the growth and fabrication of devices in three different material groups: AlGaAs/GaAs, AlInGaP, and AlGaN/GaN. Discussed are GaN blue light-emitting diodes (LEDs), AlInGaP red and yellow LEDs, and AlGaAs/GaAs vertical cavity surface-emitting lasers and high-electron-mobility transistors. Based on these examples, the evolution of MOCVD technology from fundamental materials studies and advanced materials development through the early stages of pilot manufacturing and large-volume manufacturing capabilities is demonstrated.

Carrier transport in organic light-emitting diodes

Several issues related to the organic electroluminescence devices are reviewed. Numerical simulation results are presented for the trap-charge limited conduction processes. Detailed band and charge profiles reveal the physics governing the carrier conduction processes. The numerical model is also applied to the case of doping and various possible effects are studied.

Organic electroluminescence displays

Recently, organic light emitting diodes have received a lot of attention in different research laboratories world-wide. Red, green and blue emitting devices are readily available. Devices with luminous efficiencies greater than 15 lm/W and lifetimes longer than 10,000 hours have been demonstrated. In this article, we will discuss the basic devices used in physics, materials used in organic light emitting diodes, device degradation mechanisms, and the opportunities of using this technology for commercial display applications.