Circularised Polarised OLEDs

About

About this Technology Scientists at Imperial College have developed a patented approach to fabricate polymer light emitting diodes (PLEDs), using solution-processed materials, where the emission is substantially circularly polarised (CP). The unique approach uses an intrinsically chiral chemical dopant. The chiral additive is simply mixed with a conventional achiral light-emitting polymer during processing. Without the chiral small molecule, the emission is non-polarised. The core potential application of such CP-PLEDs is in flat panel displays (FPDs). Firstly, as an alternative LCD backlight, potentially doubling efficiency by halving the light lost at the first polariser layer. Secondly as the emitting elements in AMOLED displays, again potentially doubling efficiency by halving the light lost at the contrast enhancing CP surface filter. Current technologies use an unpolarised light source together with a wide-band reflective polariser to engineer a CP output. This has limitations in terms of simplicity, compactness, energy efficiency and product cost, when compared with future technologies based on LEDs that directly emit CP light. Other potential technical solutions are complex and expensive and have not been adopted for commercial use. This new approach is simple to manufacture and highly translatable, requiring a conventional material set, device process flow and device architecture, but with the addition of a chiral molecular dopant to the light emitting polymer solution prior to its deposition: this changes PLED emission from non-polarised to circularly polarised.