Organic light-emitting diodes produce the vivid colours of modern screens, but the materials have never survived photolithography, the chemical patterning process at the heart of chip manufacturing. A team led by Yinyin Bao, who carried out the research at ETH Zurich before becoming a professor at the University of Helsinki, together with ETH professor Chih-Jen Shih, has now designed light-emitting polymers that double as photoresists. The work is reported in Nature.
Each molecule has a core-shell architecture: a colour-emitting core surrounded by star-like arms whose outer ends cross-link under ultraviolet light, rendering exposed areas insoluble so the unexposed material can be washed away. The inner sections of the arms hold the reactive chemistry at a distance, shielding the delicate emitter from damage during patterning. Collaborators at RMIT University in Melbourne ran computer simulations of this protective effect.
To demonstrate the approach, the researchers printed a multicolour fluorescent image of a macaw measuring 300 by 430 micrometres with 250 by 350 pixels, described as the highest-resolution multicolour fluorescent image yet made with photolithography, alongside an electrically driven ETH logo of 1 by 2.4 millimetres. The technique could yield sharp microdisplays for augmented-reality glasses, miniature light sources for medical technology, and emitters built directly onto microchips for microscopy and sensing.