Organic Light-Emitting Diode with Highly Ordered Polycrystalline Thin Film

Abstract

We investigate organic light-emitting diodes with a polycrystalline thin film of a calamitic liquid-crystalline material. Compared to a non-liquid-crystalline material, the polycrystalline films fabricated via the liquid-crystalline phase showed high electrical current and light emission from an emissive dye dopant, in spite of a film thickness of over 1 µm. Judging from the X-ray diffraction patterns and polarized optical microscope images, well-controlled parallel molecular orientation and suppression of grain boundaries were achieved only in the liquid-crystalline material owing to the molecular orientation controllability of the liquid-crystalline materials. We conclude that the liquid-crystalline materials can be a good candidate for a polycrystalline organic semiconductor for not only thin-film transistors but also light-emitting diodes and solar cells.