Stable and efficient white emissive fluorescent/phosphorescent complex device

Abstract

Over the past decade, much effort has been devoted to the conjugated polymers with semi-conducting properties due to their applicability in the field of optic and optoelectric devices such as light-emitting diodes, photovoltaic devices, transistors and lasers. In particular, the LEDs based on conjugated polymers have attracted much attention because of their good processability, low operating voltage, fast response times, and facile color tunability over the full visible range which well suitable for flat-panel displays. Organic and polymer light-emitting diodes(OLEDs/PLEDs) that emit white light are attracting increasing interest for their potential applications as full color displays, backlights for liquid-crystal displays, and even next-generation paper-thin light source. Various strategies have been utilized to fabricate polymeric whitelight-emitting diodes. The firstly proposed method was multilayer structure device, but nowadays single layer structure is preferred due to its low production cost and easy processability. In single layer structure, emissive layer consists of several polymers, electron and hole transport material [for balance of charge carriers] as well as luminous polymers. However, most polymers are not miscible each other due to the low entropy of mixing, phase separation occurred when the thin film from solution was fabricated. This phase separation causes some problems such as color change by applied voltage and low efficiency.