Electroluminescent device including semiconductor nanocrystal and cyanide group and display device including the same
An electroluminescent device including a first electrode; a second electrode; and a light emitting layer disposed between the first electrode and the second electrode, wherein the light emitting layer includes a plurality of semiconductor nanoparticles and does not include cadmium, wherein the light emitting layer further includes a chemical species including a cyanide group including a cyano group, a cyanide anion, or a combination thereof, and wherein the chemical species includes a bond between a metal and the cyanide group.
1 . A method of producing an electroluminescent device,
wherein the electroluminescent device comprises:
a first electrode;
a second electrode; and
a light emitting layer disposed between the first electrode and the second electrode,
wherein the light emitting layer comprises a plurality of semiconductor nanoparticles and does not comprise cadmium,
wherein the light emitting layer further comprises a cyanide anion, a chemical species comprising a cyanide moiety, or a combination thereof
wherein the chemical species comprises a bond between a metal and the cyanide moiety,
wherein the light emitting layer further comprises a chemical species comprising a COO moiety,
wherein the method comprises:
forming the light emitting layer on the first electrode, and
forming the second electrode on the light emitting layer,
wherein forming the light emitting layer comprises
preparing a film comprising semiconductor nanoparticles, and
contacting the semiconductor nanoparticles with a solution of a cyanide compound, and
wherein the cyanide compound comprises potassium cyanide, sodium cyanide, lithium cyanide, rubidium cyanide, cesium cyanide, a tetraalkyl ammonium salt cyanide, or a combination thereof.
2 . The method of claim 1 ,
wherein the electroluminescent device further comprises an electron auxiliary layer disposed between the light emitting layer and the second electrode, wherein the electron auxiliary layer is configured to inject, transport or inject and transport an electron, or
wherein the electroluminescent device further comprises a hole auxiliary layer between the light emitting layer and the first electrode.
3 . The method of claim 1 , wherein the light emitting layer comprises an alkali metal cyanide, an ammonium salt cyanide, a hydrogen cyanide, a cyanide group derived therefrom, or a combination thereof.
4 . The method of claim 1 , wherein the semiconductor nanoparticle comprises a Group II-VI compound, a Group III-V compound, a Group IV-VI compound, a Group IV element or compound, a Group I-III-VI compound, a Group II-III-VI compound, a Group I-II-IV-VI compound, or a combination thereof.
5 . The method of claim 1 , wherein the semiconductor nanoparticle has a size of greater than or equal to about 2 nanometers and less than or equal to about 50 nanometers.
6 . The method of claim 1 , wherein the light emitting layer exhibits at least one peak assigned to a cyanide group in a wavenumber range of about 1,900 inverse centimeters and about 2,300 inverse centimeters in a Fourier transform infrared spectroscopy analysis.
7 . The method of claim 6 , wherein the peak assigned to the cyanide group comprises a first peak, a second peak, or a combination thereof, wherein the first peak is present in a wavenumber range of 2,000 inverse centimeters to 2,150 inverse centimeters, and the second peak is present in a wavenumber range of 2,100 inverse centimeters to 2,300 inverse centimeters.
8 . The method of claim 1 ,
wherein the light emitting layer exhibits a peak assigned to a COO moiety in a wavenumber range of about 1,400 inverse centimeters to about 1,650 inverse centimeters in a Fourier transform infrared spectroscopy analysis, and
wherein a ratio of a normalized intensity of the peak assigned to a cyanide group to a normalized intensity of the peak assigned to the COO moiety is greater than or equal to about 0.03:1 and less than or equal to about 1:1.
9 . The method of claim 1 ,
wherein the plurality of semiconductor nanoparticles comprises a zinc chalcogenide, the plurality of semiconductor nanoparticles further comprises an organic ligand, and in the plurality of semiconductor nanoparticles a mole ratio of carbon to zinc is greater than or equal to about 1.5:1 and less than or equal to about 4:1.
10 . The method of claim 1 , wherein the electroluminescent device further comprises an electron auxiliary layer disposed between the light emitting layer and the second electrode, and a difference between a lowest unoccupied molecular orbital energy level of the light emitting layer and a lowest unoccupied molecular orbital energy level of the electron auxiliary layer is greater than or equal to about 0.001 electronvolts and less than or equal to about 0.9 electronvolts.
11 . The method of claim 1 , wherein the electroluminescent device has a maximum external quantum efficiency of greater than or equal to about 10% or a maximum luminance of greater than or equal to about 50,000 candelas per square meter.
12 . The method of claim 1 , wherein the electroluminescent device exhibits a T50 of greater than or equal to about 50 hours, as measured by operating the device at 650 candelas per square meter, or
wherein the electroluminescent device exhibits a voltage difference between an initial voltage and a voltage at T50 of less than 1 volt.
13 . The method of claim 1 , wherein the contacting is carried out by applying the solution of the cyanide compound on the film comprising semiconductor nanoparticles.
14 . The method of claim 1 , wherein the cyanide compound comprises potassium cyanide, sodium cyanide, or a combination thereof.