# Ajou University and partners design a metal-free organic emitter with 12 µs blue phosphorescence in a PMMA film

- Published: 2026-11-09 02:46 UTC
- Section: Machines & Making › Electronics
- Tags: metal-free phosphorescence, fast organic phosphorescence, blue room-temperature phosphorescence, iridium-free OLED emitter, directional carbonyl orientation, spin-orbit coupling, Angewandte Chemie, PMMA film emitter, bio-imaging phosphors
- URL: https://realtech.media/news/rt-9ce92c4561ed4007d88bb0c1_ajou_university_and/

**An international team showed that the twist direction of two carbonyl groups sets phosphorescence speed in organic molecules. The lab-stage result may help reduce reliance on iridium emitters.**

![Ajou University and partners design a metal-free organic emitter with 12 µs blue phosphorescence in a PMMA film](https://realtech.media/media/2026/11/60a474b7ca52d4af.jpg)
*Samsung Galaxy Note 10, Wikimedia Commons, CC BY-SA 4.0*

A joint team from Ajou University, the University of Michigan and Seoul National University has proposed a design principle for metal-free organic molecules that emit fast blue phosphorescence at room temperature, with lifetimes in the microsecond range, according to unimatea.co.kr. The work was published in Angewandte Chemie International Edition. [1]

Phosphorescence in OLEDs matters because about 75% of the excited energy created by electric current is in the triplet state, which fluorescent materials cannot convert to light. Red and green OLED emitters currently use phosphorescent compounds containing iridium, a rare and expensive element, and the article notes toxicity and stability issues. Heavy atoms speed up triplet emission through spin-orbit coupling. Purely organic phosphors lack this, so their emission usually lasts milliseconds to seconds, which causes image persistence and efficiency losses in displays. [1]

## Twist direction of carbonyl groups

The team studied the model molecule MeBrTPA: a benzene ring with a carbonyl group (C=O) on each side and a bromine atom nearby. Both carbonyl groups are slightly twisted out of the ring plane. The authors found that the direction of the twist matters more than its angle, and named the concept directional carbonyl orientation (DCO). [1]

Two crystal forms of MeBrTPA both emitted blue light at about 450 nm. In Form I, where the groups twist in the same direction, the phosphorescence lifetime was 15 µs. In Form II, with opposite twists, it was 80 µs, about five times longer. Ethyl, butyl and hexyl derivatives all crystallized with opposite twists and showed slow lifetimes of 120–210 µs. [1]

Quantum-chemical calculations indicated that with opposite twists the molecule is centrally symmetric and the relevant spin-orbit coupling nearly cancels. With the same twist direction the symmetry breaks and the coupling becomes hundreds of times larger. The authors add that interactions with neighboring molecules in the crystal also affect the emission pathway. [1]

## A locked molecule in a plastic film

Because crystal packing is hard to control, the team built the favorable geometry into the molecule. In the new compound CyclicBrTPA, two bromine-bearing terephthalic units are joined by a short chain so that the twist stays in the same direction. [1]

Mixed at 0.01–1% into a PMMA film, it produced blue phosphorescence with a lifetime of about 12 µs without crystallization. Over a hundredfold change in concentration, efficiency and speed stayed almost unchanged. In solution the molecule does not emit at room temperature, so a rigid solid matrix is still required. [1]

The authors say possible uses include metal-free OLED emitters and bio-imaging, where microsecond emission allows separating a signal from short-lived background fluorescence. Lead author Prof. Heo of Ajou University noted that applying the material in devices will require follow-up work to raise emission efficiency. [1]

## Sources

1. [unimatea.co.kr](https://www.unimatea.co.kr/news/articleView.html?idxno=17009)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-9ce92c4561ed4007d88bb0c1_ajou_university_and/