We report substantially enhanced photoluminescence (PL) from hybrid structures of graphene/ZnO films at a band gap energy of ZnO (∼3.3 eV/376 nm). Despite the well-known constant optical conductivity of graphene in the visible-frequency regime, its abnormally strong absorption in the violet-frequency region has recently been reported. In this Letter, we demonstrate that the resonant excitation of graphene plasmon is responsible for such absorption and eventually contributes to enhanced photoemission from structures of graphene/ZnO films when the corrugation of the ZnO surface modulates photons emitted from ZnO to fulfill the dispersion relation of graphene plasmon. These arguments are strongly supported by PL enhancements depending on the spacer thickness, measurement temperature, and annealing temperature, and the micro-PL mapping images obtained from separate graphene layers on ZnO films.
Transparent conductive electrodes (TCEs) are widely used in a wide range of optical-electronic devices. Recently, metal nanowires (NWs), e.g. Ag and Cu, have drawn attention as promising flexible materials for TCEs. Although the study of core-shell metal NWs, and the encapsulation/overcoating of the surface of single-metal NWs have separately been an object of focus in the literature, herein for the first time we simultaneously applied both strategies in the fabrication of highly stable Ag-Cu NW-based TCEs by the utilization of Ag nanoparticles covered with reduced graphene oxide (rGO). The incorporation of Ag nanoparticles by galvanic displacement reaction was shown to significantly increase the long term stability of the electrode. Upon comparison with a CuNW reference, our novel rGO/Cu-AgNW-based TCEs unveiled remarkable opto-electrical properties, with a 3-fold sheet resistance decrease (from 29.8 Ω sq to 10.0 Ω sq) and an impressive FOM value (139.4). No detrimental effect was noticed in the relatively high transmittance value (T = 77.6% at 550 nm) characteristic of CuNWs. In addition, our rGO/Cu-AgNW-based TCEs exhibited outstanding thermal stability up to 20 days at 80 °C in air, as well as improved mechanical flexibility. The superior performance herein reported compared with both CuNWs and AgNWs, and with a current conventional ITO reference, is believed to highlight the great potential of these novel materials as promising alternatives in optical-electronic devices.
Organic
electronic devices such as organic light-emitting diodes
(OLEDs), quantum dot LEDs, and organic photovoltaics are promising
technologies for future electronics. However, achieving long-term
stability of organic-based optoelectronic devices has been regarded
as a crucial problem to be solved. In this work, a simple and reproducible
fabrication method for ultralow water permeation barrier films having
a triple-layered (triad) hydrogenated silicon nitride (a-SiN
x
:H)/nanosilicon oxynitride (n-SiO
x
N
y
)/hybrid silicon oxide (h-SiO
x
) multistructure is presented. Two triad
(a-SiN
x
:H/n-SiO
x
N
y
/h-SiO
x
)
n=2 multistructure barrier films
are deposited on both sides of a poly(ethylene terephthalate) substrate
using a combination of low-pressure plasma-enhanced chemical vapor
deposition and dip coating. The deposited films show a high average
transmittance (400–700 nm) of 84% and an ultralow water vapor
transmission rate of 2 × 10–6 g/m2/day. In the electroluminescence characteristics of OLEDs encapsulated
with two triad barrier films, the operational lifetime (T
50) of OLEDs is 1584 h, which is almost similar to that
(1416 h) of OLEDs encapsulated with a glass lid.
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