Researchers at the University of Waterloo in Canada have integrated nanowire diodes, free-standing vertically, on a flexible sheet of polyethylene terephthalate (PET).
Because the light-emitting active area is at the top of the nanowires, bending the substrate does not create stress in this active area, which prevents performance degradation in the LEDs. The researchers published their results under the heading “Optically invariant InGaN nanowire light-emitting diodes on flexible substrates under mechanical manipulation” in Nature’s Journal of Electronics.
This was observed by experimenting with 1 × 1 mm2 nanowires, with a switching voltage of 2.5 V and a current voltage of 400 μA at 4V. Through finite element analysis and three-dimensional time domain modeling with finite difference, the researchers were able to attribute the increase in electroluminescence intensities with constant I-V characteristics to improved electromagnetic coupling between LED nanowires as their tips get closer. Concave bending did not affect the electrical properties or the peak emission wavelength of the LEDs.
Such NW LEDs on flexible substrates are expected to be developed for conformal illumination and wearable displays.