Abstract
Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red–green–blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000 cd m−2 at 7 V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics.
Highlights
Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays
Among various light-emitting devices, colloidal quantum dot light-emitting diode (LED) (QLEDs) have attracted great attention as next-generation displays based on electroluminescence (EL)[16,17,18,19,20,21,22,23]
For full-colour wearable QLED displays, the red–green–blue (RGB) subpixels should be precisely aligned with high resolution, which cannot be realized by the conventional solution processes[39,40]
Summary
White LEDs fabricated by transfer printing of RGB QDs. Our intaglio transfer printing technique can be utilized to create highperformance pixelated white QLEDs (PWQLEDs) on flexible substrates (Fig. 3a). EL efficiencies are compared between PWQLEDs and mixed white QLEDs (MWQLEDs) in which the active layer is created by mixing RGB QDs in the solution phase (Supplementary Methods for fabrication details). These ultra-thin QLEDs can be laminated on various curvilinear substrates, such as the crumpled Al foil, human skin, round glass, metal can and sharp edges of a slide glass (Fig. 4e–g, Supplementary Fig. 13a–d). The current electronic tattoo platform can be extended to wearable PWQLEDs that are laminated on the human skin (Fig. 4h)
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