Organic Resonant-Cavity-Enhanced LEDs: The primary enabler of the new generation of microdisplays

Student: Van Nguyen

Supervisor: Aleksandar Rakic

Category: Engineering Thesis Project - Communications

Recently organic light emitting diodes (OLEDs) have emerged as ideal transducers for use with silicon active-matrix chips to enable the new generation of microdisplays. The attractiveness of such OLED structures is the realisation of its low weight, low cost, ease of fabrication, full colour range and the opportunity of fabrication on a large scale.

The major drawback of these devices is their colour impurity caused by the wide spectral halfwidths exhibited by the emissive elements. By implementing a photonic bandgap structure, an optical microcavity can be formed either by using metallic reflectors or Distributed Bragg Reflectors (DBR). Purer colour, sharper emission and a more directive emission can then be realized. In some applications, microcavity effects are desired to achieve directionality and colour saturation. However in most application the microcavity effects distort and cause angular dispersion on both the intensity and colour variations of the enhanced emissions. For full colour displays, microcavity enhanced emission intensity over a large range of angles, the colour variations needs to remain at a minimum.

This thesis used optical multilayers filters to simulate the DBR microcavity and investigate its angular dispersion characteristics. It is concluded that by increasing the number of layers in the DBR stack will lead to an increases in sensitivity to angular dispersion and colour variations. However for microdisplay applications, where displays are viewed close to the eyes with the aid of optical lenses. The highly directive radiative patterns of these devices are the perfect choice of emissive unit.

Thesis Document (PDF)

Poster Presentation (PDF)