Summary
Researchers report electroluminescent photoresists that can be patterned with ultraviolet and electron-beam lithography. The materials produced 110-nm features and multicolour OLED pixels with a peak external quantum efficiency of 13.3%.
Researchers have developed a class of organic light-emitting materials that can be patterned like a semiconductor photoresist. In a Nature paper published on 16 September 2026, the team reports electroluminescent photoresists, or ELPRs, patterned with ultraviolet and electron-beam lithography, including features with critical dimensions down to 110 nanometres.
The same material platform produced directly patterned OLEDs with a peak external quantum efficiency (EQE) of 13.3% and a working multicolour array with 30-micrometre pixels. EQE measures the proportion of injected charge that emerges from an OLED as externally emitted photons.
How the electroluminescent photoresist works
OLED emissive layers are traditionally deposited by vacuum evaporation or inkjet printing. Those approaches can produce high-quality devices, but they do not fit naturally into the lithographic processes used to build silicon electronics. Standard photolithography also exposes organic semiconductors to solvents, developers and reactive chemicals that can damage their light-emitting properties.
The new ELPRs address this compatibility problem through a multi-arm star-polymer architecture made using atom transfer radical polymerization. Each polymer contains a thermally activated delayed fluorescence (TADF) emitter at its core, an inner host shell and a reactive outer region. TADF materials can recover some excited triplet states through thermally assisted reverse intersystem crossing, allowing those states to contribute to light emission.
The host shell is designed to keep the emissive core away from the chemical reactions used to pattern the film. For ultraviolet processing, terminal cinnamoyl groups undergo light-triggered crosslinking. The exposed regions become insoluble, while unexposed material can be removed with toluene, producing a negative-tone pattern. A separate version uses allyl groups for electron-beam lithography.
This separation is central to the design. Molecular-dynamics simulations indicated that host units generally surround the emitter cores while crosslinking groups from neighbouring polymers are positioned to react with one another. The arrangement is intended to preserve the optical and electrical behaviour of the emitter while giving the surrounding film the mechanical and chemical stability needed for development.
Lithographic resolution and OLED performance
Ultraviolet-patterned green ELPR films produced line-and-space patterns with a 4/2-micrometre pitch. The researchers also performed three sequential photolithography cycles to integrate blue, green and red emissive materials without dissolving earlier layers.
Electron-beam versions extended the resolution further. A green ELPR produced line-and-space pitches of 110/160 nanometres, while multicolour electron-beam patterning generated fluorescent pixels with dimensions down to 200 nanometres. The patterns also retained their photoluminescence after exposure to aggressive processing conditions, including warm acetone in one test structure.
The researchers first improved the underlying polymer OLEDs by removing bromide end groups left by the polymerization process. In an un-crosslinked green self-hosted polymer, this change increased maximum EQE from 1.6% to over 30.3% and increased current efficiency from 4.25 to 75.44 candela per ampere. The fully patterned G-ortho-ELPR device achieved a peak EQE of 13.3% after ultraviolet crosslinking.
The team then fabricated a multicolour OLED array using three sequential patterning cycles. Blue, green and red pixels formed the letters “ETH”; the circular pixels had a diameter of 30 micrometres and showed uniform electroluminescence at 6 volts. This demonstrates the intended process advantage: several organic emissive layers can be aligned and integrated on one device rather than separately assembled.
Operational lifetime remains the main device constraint reported in the study. Crosslinked G-ortho-ELPR devices reached an LT50—the time for luminance to fall to half its initial value—of about 70 minutes at a constant current density of 1 mA cm−2 in the baseline configuration. After reducing residual copper through dialysis and changing the charge-transport layers, a crosslinked device reached an LT50 of 146 minutes at 2.4 mA cm−2. The paper identifies trace-metal impurities, transport-layer interactions and possible weak chemical bonds as important targets for further stability improvements.
The results establish a route for combining OLED emission with semiconductor-style lithography. If the materials' efficiency and lifetime can be improved together, the approach could support densely integrated organic microdisplays and light sources for on-chip photonics.