ELECTROLUMINESCENT DEVICE, PRODUCTION METHOD THEREOF, AND DISPLAY DEVICE INCLUDING THE SAME
A method of producing an electroluminescent device, the method including: disposing a light emitting layer including a semiconductor nanoparticle on a first electrode; applying a composition including a zinc oxide nanoparticle onto the light emitting layer to form an electron transport layer, the zinc oxide nanoparticle including a first metal and an alkali metal; and disposing the second electrode on the electron transport layer to produce the electroluminescent device, wherein a preparation of the zinc oxide nanoparticle includes admixing a first solution including a zinc precursor and a first metal precursor in a solvent with a second base and optionally a first base to prepare the zinc oxide nanoparticle, wherein the first base includes an organic base containing a C1 to C50 organic group, and the second base includes an inorganic base including the alkali metal.
1 . A method of producing an electroluminescent device, the method comprising:
disposing a light emitting layer comprising a semiconductor nanoparticle on a first electrode;
applying a composition comprising a zinc oxide nanoparticle on the light emitting layer to form an electron transport layer, the zinc oxide nanoparticle comprising a first metal different from zinc and an alkali metal; and
disposing the second electrode on the electron transport layer to produce the electroluminescent device,
wherein a preparation of the zinc oxide nanoparticle comprises
admixing a first solution comprising a zinc precursor and a first metal precursor in a solvent with a second base and optionally a first base to prepare the zinc oxide nanoparticle,
wherein the first base comprises an organic base comprising a C1 to C50 organic group, and the second base comprises an inorganic base comprising the alkali metal.
2 . The method of claim 1 ,
wherein
the first metal comprises an alkaline earth metal, zirconium, tungsten, titanium, yttrium, aluminum, gallium, indium, tin, cobalt, vanadium, or a combination thereof, and
the alkali metal comprises sodium, potassium, rubidium, cesium, francium, or a combination thereof, and
optionally wherein the first solution is prepared by dissolving the zinc precursor and the first metal precursor in the solvent.
3 . The method of claim 1 , wherein the first base comprises a quaternary ammonium salt, and the second base comprises a hydroxide of the alkali metal.
4 . The method of claim 1 , wherein a mole ratio of the second base to the first base is from about 1:0 to about 1:10.
5 . The method of claim 1 , wherein when the zinc oxide nanoparticle is analyzed by ultraviolet-visible absorption spectroscopy,
a wavelength of a first absorption peak in an ultraviolet-visible absorption spectrum is greater than or equal to about 285 nanometers and less than or equal to about 300 nanometers, and
optionally wherein the ultraviolet-visible absorption spectrum has a valley that is adjacent to the first absorption peak, and a valley depth of the valley, defined by Equation 1, is greater than or equal to about 0.03 and less than or equal to about 0.15:
1
-
(
Abs
valley
/
Abs
first
)
=
VD
(
1
)
wherein Abs first is an absorbance at the wavelength of the first absorption peak and Abs valley is an absorbance at a lowest point of the valley, and VD is the valley depth.
6 . The method of claim 1 , wherein the zinc oxide nanoparticle has a bandgap energy of greater than or equal to about 3.6 electronvolts and less than or equal to about 3.95 electronvolts; or
wherein the zinc oxide nanoparticle has a size of greater than or equal to about 1 nanometer and less than or equal to about 50 nanometers.
7 . The method of claim 1 , wherein in the zinc oxide nanoparticle, a mole ratio of the alkali metal to the first metal is greater than or equal to about 0.05:1 and less than or equal to about 1.5:1.
8 . The method of claim 1 , wherein in the zinc oxide nanoparticle, a mole ratio of the alkali metal to zinc is greater than or equal to about 0.01:1 and less than or equal to about 0.5:1.
9 . The method of claim 1 , wherein in the zinc oxide nanoparticle, a mole ratio of a sum of the first metal and the alkali metal to zinc is greater than or equal to about 0.1:1 and less than or equal to about 1:1.
10 . The method of claim 1 , wherein the zinc oxide nanoparticle is configured to be dispersible in a C1 to C10 alcohol solvent to form a colloidal dispersion.
11 . The method of claim 1 ,
wherein
when the zinc oxide nanoparticle is analyzed by X-ray photoelectron spectroscopy, a Zn2p peak of the zinc oxide nanoparticle is shifted to a lower binding energy than a Zn2p peak of a zinc oxide nanoparticle that is prepared using the first base and without using the second base, or
when the zinc oxide nanoparticle is analyzed by Fourier transform infrared spectroscopy, a Fourier transform infrared spectrum does not have a peak assigned to an amine group in a wavenumber range of from about 1485 centimeters −1 to about 1490 centimeters −1 .
12 . An electroluminescent device comprising:
a first electrode and a second electrode spaced apart from each other;
a light emitting layer disposed between the first electrode and the second electrode; and
an electron transport layer disposed between the light emitting layer and the second electrode,
wherein the light emitting layer is configured to emit a first light,
wherein the light emitting layer comprises a semiconductor nanoparticle,
wherein the semiconductor nanoparticle does not comprise cadmium,
wherein the electron transport layer comprises a zinc oxide nanoparticle,
wherein the zinc oxide nanoparticle has a size of greater than or equal to about 1 nanometer and less than or equal to about 50 nanometers, and comprises
a first metal and an alkali metal,
wherein
the first metal comprises an alkaline earth metal, and optionally zirconium, tungsten, titanium, yttrium, aluminum, gallium, indium, tin, cobalt, vanadium, or a combination thereof, and
the alkali metal comprises sodium, potassium, rubidium, cesium, francium, or a combination thereof.
13 . The electroluminescent device of claim 12 , wherein the first light is blue light and a peak emission wavelength of the first light is greater than or equal to about 440 nanometers and less than or equal to about 480 nanometers.
14 . The electroluminescent device of claim 12 , wherein, in the zinc oxide nanoparticle, the first metal is magnesium, and the alkali metal comprises potassium, rubidium, cesium, or a combination thereof.
15 . The electroluminescent device of claim 12 , wherein the electron transport layer is configured to exhibit a bandgap energy of greater than or equal to about 3.5 electronvolts and less than or equal to about 3.95 electronvolts.
16 . The electroluminescent device of claim 12 , wherein in the zinc oxide nanoparticle,
a mole ratio of the alkali metal to the first metal is greater than or equal to about 0.36:1 and less than or equal to about 0.7:1, and
a mole ratio of the alkali metal to zinc is greater than or equal to about 0.01:1 and less than or equal to about 0.5:1.
17 . The electroluminescent device of claim 12 , wherein in the zinc oxide nanoparticle,
a mole ratio of a sum of the first metal and the alkali metal to zinc is greater than or equal to about 0.1:1 and less than or equal to about 1:1.
18 . The electroluminescent device of claim 12 , wherein when the zinc oxide nanoparticle is analyzed by ultraviolet-visible absorption spectroscopy,
a wavelength of a first absorption peak in an ultraviolet-visible absorption spectrum is greater than or equal to about 290 nanometers and less than or equal to about 300 nanometers, and
optionally wherein the ultraviolet-visible absorption spectrum has a valley that is adjacent to the first absorption peak, and a valley depth of the valley, defined by Equation 1, is greater than or equal to about 0.03 and less than or equal to about 0.15:
1
-
(
Abs
valley
/
Abs
first
)
=
VD
(
1
)
wherein Abs first is an absorbance at the first absorption peak wavelength and Abs valley is an absorbance at a lowest point of the valley, and VD is the valley depth.
19 . The electroluminescent device of claim 12 ,
wherein the electroluminescent device is configured to emit blue light on an application of a voltage;
wherein
the electroluminescent device has a maximum external quantum efficiency of greater than or equal to about 6 percent and less than or equal to about 40 percent, or
the electroluminescent device shows a maximum luminance of greater than or equal to about 50,000 candelas per square meter and less than or equal to about 500,000 candelas per square meter; and
wherein the electroluminescent device exhibits a T90 of greater than or equal to about 50 hours as measured at an initial luminance of 650 nit.
20 . A display device comprising the electroluminescent device of claim 12 .
21 . The display device of claim 20 , wherein the display device comprises a handheld terminal device, a monitor, a notebook computer, a television, an electronic display board, a camera, or an electronic component for an automatic vehicle.