Organic–inorganic semiconductor heterojunctions for hybrid light-emitting diodes

This chapter discusses an alternative approach for generating white light through hybrid inorganic–organic light-emitting diodes (LEDs), combining blue-emitting organic LEDs with organic energy-down converters. Inorganic LEDs, based on III-nitride semiconductors, exhibit extremely high efficiencies, whereas organic color converters are low-cost and have versatile absorption and emission properties. An extensive background is provided to introduce nitride semiconductors and LEDs, but also to give the background to colorimetry and radiometry of light sources, important for the characterization of the hybrid device and an understanding of how the emission properties influence the color parameters, such as color rendering and luminous efficacy. A short introduction to the synthesis of color converters aims to illustrate the controlling factors in the design of the converter materials. Two types of organic materials will be introduced. The first are light-emitting polymers, which are readily commercially available and cost effective. The second type are luminescent small molecules, which will be discussed in more detail and the examples given showcase the evolution of a series of small molecules and their use in hybrid inorganic–organic LEDs