Overlapping-Gate Organic Light-Emitting Transistors

A light-emitting transistor in which two gates, separated by an insulator, partially overlap in the center of the device is proposed. By accumulating charge carriers in dedicated transport layers, each gate independently controls charge injection into the emissive layer sandwiched between the transport layers. This structure combines the advantages of pinned light emission in the center of the channel, gapless charge transport into the recombination zone, and controlled balance of electron and hole concentration at the edges of the emissive layer for any chosen current density. High-performance devices with overlapping gates are demonstrated: Using a red fluorescent emitter, high external quantum efficiency (5.7%) is conserved up to the highest luminance (2190 cd m(-2)). A comprehensive optoelectronic device model is proposed that verifies the measured characteristics and confirms that efficiency is highest with balanced charge transport. This device topology opens perspectives in the development of bright thin film light sources driven at high current densities.