Researchers design fast white light from hybridized inorganic/organic LED

December 04, 2017 // By Julien Happich
While today's most common approach to creating white light is to cap blue- or ultraviolet-emitting LEDs with down-conversion yellow phosphor materials, such white lights suffer from several inherent limitations, including phosphor inefficiency, stability and a relatively slow response time in the order of microseconds, which restricts their applicability to Li-Fi at bandwidths under 1MHz when unfiltered.

The use of blue filters to bypass the slow yellow response of the phosphors severely impacts the usable signal integrity.

The hybrid organic/inorganic white LED with a 2D
microhole array structure.

Working on removing the inefficiencies and technical limitations of phosphor-based white lights, a team of researchers from the University of Sheffield has designed a novel type of white LED by closely hybridizing an inorganic InGaN/GaN blue LED with pockets of organic light-emitting polymers (OLEPs).

The idea behind this hybridization is to leverage the OLEDs' much faster response time together with a highly efficient near-field non-radiative Förster resonance energy transfer (FRET) between the inorganic active region and the nearby yellow-emitting organic polymer.

It is understood that nonradiative FRET involves a near-field radiation-less energy transfer from inorganic active-regions (donors) to OLEPs (acceptors) through dipole−dipole Coulombic interactions, hence the need to minimize the separation between donor and acceptor dipoles so they can interact.

The researchers started with a commercial blue InGaN/GaN LED wafer grown on c-plane sapphire, with a 160nm thick InGaN/GaN MQW active region.

In a paper titled "Electrically Injected Hybrid Organic/Inorganic III-Nitride White LightEmitting Diodes with Nonradiative Förster Resonance Energy Transfer" published in ACS Photonics, they detail how they patterned a two-dimensional microhole array structure deep across the MQW active region to drop cast a yellow-emitting polyfluorene copolymer.