A reversible ultraviolet process let researchers pattern green quantum-dot films for a light-emitting device with 21,000 pixels per inch (PPI). A paper published Sept. 24 in Nature Communications reports that the pixelated device reached 17.08% peak external quantum efficiency, the ratio of photons leaving the LED per electron injected.
Quantum dots are light-emitting semiconductor nanocrystals. Small molecules called ligands coat their surfaces and affect their stability and light emission. Direct photolithography can pattern the dots without a separate photoresist, but exposure and solvent development can alter those surface molecules.
Chang Gu and colleagues attached a light-sensitive, coumarin-based ligand to commercial green CdSe/ZnS quantum dots. Ultraviolet light centered at 310 nanometers linked the ligands in illuminated areas. During toluene development, unexposed dots washed away, leaving a pattern. A second exposure at 254 nanometers broke the links, undoing the temporary crosslinking and restoring the dots’ structure and function, the authors report.
A separate, non-pixelated green device reached 24.41% peak external quantum efficiency; the high-density pixelated device reached 17.08%.
Supplementary tests found that the dots’ photoluminescence quantum yield—the fraction of absorbed light emitted again—declined over repeated crosslinking and reversal cycles. The team also patterned red, green and blue films, but its 21,000-PPI light-emitting device used green dots. A high-density RGB device remains a further test.
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Image: Figure 1 by Gu et al., Nature Communications (2026), reused under CC BY 4.0.