Mechanism and quantum efficiency of yellow emission at the organic-inorganic F8T2/p-GaN interface

An organic/inorganic F8T2/gallium nitride (GaN) hybrid light-emitting device is fabricated and found to emit white light. The white light emission is determined to be the combination of the blue emission of the GaN light-emitting diode and the yellow emission of the F8T2 layer. Analysis of the results of this work reveals the following: (1) the yellow emission of the F8T2 layer in the F8T2/GaN light-emitting device is caused by both electroluminescence and photoluminescence and (2) the origin of the majority of the yellow emission is the electroluminescence mechanism. A potential barrier in the valence band at the F8T2/p-GaN interface has been observed and determined to be 1.05 eV by ultraviolet photoelectron spectroscopy analysis. The number of hole carriers flowing over the potential barrier (1.05 eV) into the valence band of GaN; multiple quantum wells (MQWs) governs the quantum efficiency of the yellow emission. Because the percentage of the overflowed hole carriers in the valence band increases with the current input, the quantum efficiency of the active region in the F8T2 layer increases with the current input; this observed behavior is opposite to that of existing solid-state light-emitting devices.