We report the first demonstration
of flexible white phosphor-converted
light emitting diodes (LEDs) based on p–n junction core/shell
nitride nanowires. GaN nanowires containing seven radial In0.2Ga0.8N/GaN quantum wells were grown by metal–organic
chemical vapor deposition on a sapphire substrate by a catalyst-free
approach. To fabricate the flexible LED, the nanowires are embedded
into a phosphor-doped polymer matrix, peeled off from the growth substrate,
and contacted using a flexible and transparent silver nanowire mesh.
The electroluminescence of a flexible device presents a cool-white
color with a spectral distribution covering a broad spectral range
from 400 to 700 nm. Mechanical bending stress down to a curvature
radius of 5 mm does not yield any degradation of the LED performance.
The maximal measured external quantum efficiency of the white LED
is 9.3%, and the wall plug efficiency is 2.4%.
A flexible
nitride p-n photodiode is demonstrated. The device consists
of a composite nanowire/polymer membrane transferred onto a flexible
substrate. The active element for light sensing is a vertical array
of core/shell p–n junction nanowires containing InGaN/GaN quantum
wells grown by MOVPE. Electron/hole generation and transport in core/shell
nanowires are modeled within nonequilibrium Green function formalism
showing a good agreement with experimental results. Fully flexible
transparent contacts based on a silver nanowire network are used for
device fabrication, which allows bending the detector to a few millimeter
curvature radius without damage. The detector shows a photoresponse
at wavelengths shorter than 430 nm with a peak responsivity of 0.096
A/W at 370 nm under zero bias. The operation speed for a 0.3 ×
0.3 cm2 detector patch was tested between 4 Hz and 2 kHz.
The −3 dB cutoff was found to be ∼35 Hz, which is faster
than the operation speed for typical photoconductive detectors and
which is compatible with UV monitoring applications.
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