Single-emitter white OLEDs could cut costs and chemicals in next generation lighting

TURKU, FINLAND, November 3, 2025 /EINPresswire.com/ -- In an effort to create simpler next-generation lighting solutions, researchers from the University of Turku in Finland have developed a colour-tunable white OLED. It is a top light-emitting device that produces white light from a single organic layer and two standard aluminum electrodes, eliminating the need for scarce indium tin oxide. This streamlined design replaces the need for complex organic stacks with smart optics, which promises to lower manufacturing costs and reduce reliance on scarce materials.

White OLEDs power premium screens and are becoming more common in lamps and architectural lighting. However, conventional white OLEDs are complicated. Manufacturers mix red, green, and blue dopants containing heavy metals and add a transparent indium tin oxide (ITO) layer. By mixing these colour-emitting additives in precise ratios with the host organic layer, the device produces white light. However, these steps increase costs and waste and are not sustainable.

In a recent study, researchers from the University of Turku developed a new innovative approach. They used a standard sky-blue, metal-free TADF molecule (DMAC-DPS) and reshaped its light using a tiny optical “hall of mirrors” known as a microcavity.

This new device is top-emitting and ITO-free. Both mirrors of the microcavity are made from common aluminum and work as electrodes. The light-emitting layer is a single-component thin film based on the 3rd-generation emitter DMAC-DPS, thereby avoiding the cost and complications associated with conventional host–guest chemistry and RGB colour mixing.

Microcavities can be compared to a tiny hall of mirrors because they reflect light in a similar way. In the new OLED technology developed by the researchers, adjusting the cavity length (for example, by changing the thickness of the emissive layer) shifts which colours in the OLED are reinforced. At the same time, ripples of electromagnetic energy that travel along the metal surfaces, known as surface plasmon polaritons (SPPs), blend with the cavity’s resonances to spread the spectrum from blue to white.

Together, these effects produce tunable white light from about 3,790 K (warm white) to about 5,050 K (cool white) without adding any extra materials.
“Our breakthrough is about getting more with less,” says Manish Kumar, the lead researcher. “We show that you do not need a complicated RGB colour mixing to get beautiful white light. By letting a carefully designed cavity and surface plasmons do the mixing, we turn a single, blue emitter into a tunable white OLED without ITO and with a much simpler stack, using materials already familiar to manufacturers”.

The researchers’ invention could significantly reduce the ecological footprint and cost of OLED manufacturing, as it requires fewer scarce inputs and fewer processing steps. In addition, its design fits neatly into existing vacuum-deposition production lines. Because the device is “top-emitting,” it can work well on reflective or flexible surfaces, opening options for sleek luminaires, thin backlights, and future smart-building panels.

“This work shows how clever optical design can replace chemical complexity,” says Konstantinos Daskalakis, Professor and leader of the research group. “By removing ITO and heavy-metal dopants, we are pointing to lighting that is not just efficient, but also easier to manufacture, more sustainable, and kinder to the environment and the supply chains”.

Next step for the researchers is to explore brightness, efficiency, and long-term stability in order to advance lab prototypes into real-world lighting products.

The study was published in Advanced Optical Materials.

Konstantinos S. Daskalakis
University of Turku
communications@utu.fi