Ultraviolet (UV) organic optoelectronic devices have been attracting extensive research owing to their great potential in a variety of applications such as biological and chemical sensing, excitation lighting source, high-density...
The photovoltaic performances of solar cells have been significantly improved by incorporating biomass-converted carbon quantum dots with graded energy levels into sensitized devices.
The issue of device durability is scarcely reported for state‐of‐the‐art UV organic light‐emitting diodes (UV OLEDs), but it is of theoretical interest and plays a key role in commercial products. Herein, the effects of aging time on current density and radiance of near‐UV OLEDs are investigated. Devices are fabricated with 9‐(4′‐(4,5‐diphenyl‐4H‐1,2,4‐triazol‐3‐yl)‐(1,1′‐biphenyl)‐4‐yl)‐9H‐carbazole as the fluorescent molecule, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) as the hole injection layer, and LiF as the electron injection layer. It is found that the current density decays much faster than radiance, and accordingly promotes the device external quantum efficiency from 2.5% initially to a giant value of 8.2% after a certain period of aging. Impedance spectroscopy is performed to study the carrier injection/transport capability by configuring a hole‐only cell (HOC) and an electron‐only cell (EOC). The transition curves of the impedance, phase, and capacitance as a function of voltage indicate that carrier injection/transport gradually decreases during aging, which accounts for the reduced current density and radiance. The electroluminescence spectra are independent of the decay process. The results provide a new approach for analyzing durability and advancing applications of UV OLEDs.
Solution-processed ethanol tungsten disulfide and its doping in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (
P
E
D
O
T
:
P
S
S
+
W
S
2
) for tailoring hole injection in near ultraviolet organic light-emitting diodes (NUV OLEDs) are investigated in detail. Raman spectrum, scanning electron microscopy, atomic force microscopy, x-ray/ultraviolet photoelectron spectroscopy, and impedance spectroscopy measurements show that
W
S
2
and its composites have superior film morphology and exceptional electronic properties. Using 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emitter and
P
E
D
O
T
:
P
S
S
+
W
S
2
as the hole injection layer, the NUV OLED produces short-wavelength emission peaking at 404 nm and full-width at half-maximum of 53 nm. The device also gives maximum radiance of
4.7
m
W
/
c
m
2
and external quantum efficiency of 2.1%, which are superior to counterparts using
W
S
2
, UV-ozone-treated
W
S
2
, and PEDOT:PSS. The hole injection ability is enhanced by using
W
S
2
, UV-ozone-treated
W
S
2
, PEDOT:PSS, and
P
E
D
O
T
:
P
S
S
+
W
S
2
in this order. The robust hole injection contributes to carrier balance and accounts for high device performance of the fabricated NUV OLEDs. Our results pave an alternative approach for advancing OLEDs and accelerating
W
S
2
applications.
Electron injection plays a key role in electron–photon conversion properties of inverted UV–visible organic light‐emitting diodes (OLEDs). Herein, facilely prepared solution‐processed lithium carbonate (Li2CO3) formic acid and boric acid solutions for tailoring electron injection in inverted near‐UV (NUV) OLEDs are studied. Superior film morphology and exceptional electronic properties of spin‐coated Li2CO3 films are examined by atomic force microscopy, X‐ray/ultraviolet photoelectron spectroscopy, current–voltage curves, and impedance spectroscopy. Efficient inverted NUV OLEDs are assembled using wide‐bandgap molecule of 2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole as emissive layer, showing maximum radiance of 5.24 mW cm−2 (2.28 mW cm−2) and external quantum efficiency of 2.47% (2.17%) with an optimal Li2CO3 formic acid of 3 mg ml−1 (Li2CO3 boric acid of 7 mg ml−1) as electron injection tailoring. The NUV emission shows electroluminescence peaks of 404–406 nm and full width at half maximum of 52–56 nm. The results provide some feasible approaches for enhancing the performance of organic electronic devices, which require strong electron injection/extraction and accelerate industrialization.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.