# US 9,520,573 B2 · Device including quantum dots and method for making same

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- Number: US 9,520,573 B2
- Document ID: US9520573B2
- Status: Granted
- Kind: B2
- Application number: 13/422,683
- Filed: 2012-03-16
- Published: 2012-11-22
- Granted: 2016-12-13
- Earliest claimed: 2011-05-16
- Assignees: Qd Vision, Inc.
- Applicants: Zhaoqun Zhou; Peter T. Kazlas; Benjamin S. Mashford
- Inventors: Zhaoqun Zhou; Peter T. Kazlas; Benjamin S. Mashford
- Web page: https://patentgrep.com/patent/US9520573B2

## CPC

- C09K 11/025: {non-luminescent particle coatings or suspension media}
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- C09K 11/565: {with zinc cadmium}
- C09K 11/883: {with zinc or cadmium}
- H05B 33/14: characterised by the chemical or physical composition or the arrangement of the electroluminescent material {, or by the simultaneous addition of the electroluminescent material in or onto the light source}
- H10K 30/152: {the wide bandgap semiconductor comprising zinc oxide, e.g. ZnO}
- H10K 50/115: comprising active inorganic nanostructures, e.g. luminescent quantum dots
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- B82Y 40/00: Manufacture or treatment of nanostructures
- H10H 20/812: within the light-emitting regions, e.g. having quantum confinement structures
- H10K 30/50: Photovoltaic [PV] devices
- H10K 50/15: Hole transporting layers
- H10K 85/60: Organic compounds having low molecular weight (H10K85/10 - H10K85/50 take precedence)
- H10K 85/626: {containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene}
- H10K 85/631: {Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine}
- H10K 85/633: {comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom}
- H10K 2102/331: {Nanoparticles used in non-emissive layers, e.g. in packaging layer}
- Y02E 10/549: Organic PV cells
- Y10S 977/774: Exhibiting three-dimensional carrier confinement, e.g. quantum dots
- Y10S 977/892: Liquid phase deposition
- Y10S 977/896: Chemical synthesis, e.g. chemical bonding or breaking
- Y10S 977/95: Electromagnetic energy
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A device comprises an anode; a cathode; a layer therebetween comprising quantum dots; and a first layer comprising a material capable of transporting and injecting electrons in, or forming, contact with the cathode, the material comprising nanoparticles of an inorganic semiconductor material. In one embodiment of the device, quantum dots comprise a core comprising a first semiconductor material that confines holes better than electrons in the core and an outer shell comprising a second semiconductor material that is permeable to electrons. In another embodiment of the device, the nanoparticles comprise n-doped inorganic semiconductor material, and a second layer comprising a material capable of transporting electrons is disposed between the layer including quantum dots and the first layer, wherein the second layer has a lower electron conductivity than the first. In a further embodiment of the device, the first layer is UV treated. A method and other embodiments are also disclosed.

## Claims

### Claim 1

A light emitting device comprising:
a pair of electrodes comprising an anode and a cathode;
an emissive layer comprising electroluminescent quantum dots disposed between the electrodes, wherein the quantum dots comprise a core comprising a first semiconductor material and an outer shell surrounding the core, the outer shell comprising a second semiconductor material;
a first layer comprising an electron injection and transport material comprising nanoparticles of an n-doped inorganic semiconductor, the first layer being in contact with the cathode and positioned between the emissive layer and the cathode, wherein the n-doped inorganic semiconductor comprises zinc oxide, titanium oxide, or a mixture including at least one of the foregoing that is n-doped, and
a second layer comprising an electron transport material comprising nanoparticles of an inorganic semiconductor, the second layer being disposed between the emissive layer and the first layer, wherein the second layer has a lower electron conductivity than the first layer, and
wherein the device has a peak external quantum efficiency of at least 14% when measured over the voltage range of 1 V to 10 V.

### Claim 2 (depends on 1)

A light emitting device in accordance with claim 1 wherein the absolute value of the difference between Econduction band edge of the inorganic semiconductor material included in the second layer and ELUMO of the quantum dots is no greater than 0.5 eV measured relative to vacuum level with an energy level=0 eV.

### Claim 3 (depends on 1)

A light emitting device in accordance with claim 1 wherein the first layer is UV (ultraviolet light) treated.

### Claim 4 (depends on 1)

A light emitting device in accordance with claim 1 wherein the first semiconductor material confines holes better than electrons in the core and the second semiconductor material is permeable to electrons.

### Claim 5 (depends on 1)

A light emitting device in accordance with claim 1 wherein the absolute value of the difference between Econduction band edge of the first semiconductor material included in the quantum dot core and Econduction band edge of the second semiconductor material included in the outer shell of the quantum dot is less than the absolute value of the difference between Evalence band edge of the first semiconductor material and Evalence band edge of the second semiconductor material, wherein the differences are calculated based on the Econduction band edge and Evalence band edge values for bulk forms of the first and second semiconductor materials measured relative to vacuum level with an energy level=0 eV.

### Claim 6 (depends on 1)

A light emitting device in accordance with claim 1 wherein the device has a peak external quantum efficiency in a range from 14% to 19.1% when measured over the voltage range of 1 V to 10 V.

### Claim 7 (depends on 1)

A light emitting device in accordance with claim 1 wherein the first layer and the cathode form an ohmic contact during operation of the device.

### Claim 8 (depends on 1)

A light emitting device in accordance with claim 1 further including a layer comprising a material capable of transporting holes disposed between the layer comprising quantum dots and the anode.

### Claim 9 (depends on 1)

A light emitting device in accordance with claim 1 further including hole injection layer between the layer comprising quantum dots and the anode.

### Claim 10 (depends on 1)

A light emitting device in accordance with claim 1 wherein at least a portion of the quantum dots comprise a core comprising a first semiconductor material, a first shell surrounding the core comprising a second semiconductor material, and a second shell comprising a third semiconductor material, the second shell surrounding the first shell.

### Claim 11 (depends on 1)

A light emitting device in accordance with claim 1 wherein the device is encapsulated.

### Claim 12 (depends on 1)

A light emitting device in accordance with claim 1 wherein the device has a peak internal quantum efficiency of the device of at least about 80%.

### Claim 13 (depends on 1)

A light emitting device in accordance with claim 1 wherein the nanoparticles of an n-doped inorganic semiconductor have an average particle size less than 20 nm.

### Claim 14 (depends on 1)

A light emitting device in accordance with claim 1 wherein the nanoparticles of an n-doped inorganic semiconductor have an average particle size less than 10 nm.

### Claim 15 (depends on 1)

A light emitting device in accordance with claim 1 wherein the nanoparticles of an n-doped inorganic semiconductor have an average particle in a range from about 2 to about 6 nm.

### Claim 16 (depends on 1)

A light emitting device in accordance with claim 1 wherein the n-dopant comprises indium, aluminum, or gallium.

### Claim 17 (depends on 4)

A light emitting device in accordance with claim 4 wherein the absolute value of the difference between Econduction band edge of the first semiconductor material included in the quantum dot core and Econduction band edge of the second semiconductor material included in the outer shell of the quantum dot is less than the absolute value of the difference between Evalence band edge of the first semiconductor material and Evalence band edge of the second semiconductor material, wherein the differences are calculated based on the Econduction band edge and Evalence band edge values for bulk forms of the first and second semiconductor materials measured relative to vacuum level with an energy level=0 eV.

### Claim 18 (depends on 4)

A light emitting device in accordance with claim 4 wherein the first semiconductor material comprises CdSe and the second semiconductor material comprises CdS.

### Claim 19 (depends on 4)

A light emitting device in accordance with claim 4 having a peak EQE of at least 18% when measured over a voltage range from 1 Volt to 10 Volts.

### Claim 20 (depends on 4)

A light emitting device in accordance with claim 4 having a light turn-on voltage less than 2 Volts.

### Claim 21 (depends on 4)

A light emitting device in accordance with claim 4 having a light turn-on voltage less than 1.5 Volts.

### Claim 22 (depends on 5)

A light emitting device in accordance with claim 5 wherein the first semiconductor material comprises CdSe and the second semiconductor material comprises CdS.

### Claim 23 (depends on 5)

A light emitting device in accordance with claim 5 wherein the absolute value of the difference between Econduction band edge of the first semiconductor material included in the quantum dot core and Econduction band edge of the second semiconductor material included in the outer shell of the quantum dot is less than the absolute value of the difference between Evalence band edge of the first semiconductor material and Evalence band edge of the second semiconductor material, wherein the differences are calculated based on the Econduction band edge and Evalence band edge values for bulk forms of the first and second semiconductor materials measured relative to vacuum level with an energy level=0 eV.

### Claim 24 (depends on 10)

A light emitting device in accordance with claim 10 wherein the first semiconductor material comprises CdSe, the second semiconductor material comprises CdS, and the third semiconductor material comprises ZnS.

### Claim 25

A light emitting device including an emissive layer comprising electroluminescent quantum dots disposed between an anode and a cathode,
a first layer comprising an electron injection and transport material comprising nanoparticles of a first inorganic semiconductor material, the first layer being disposed between the layer comprising quantum dots and the cathode, wherein the first layer and the cathode form an ohmic contact during operation of the device,
wherein the first inorganic semiconductor material includes at least one of zinc oxide, a titanium oxide, a niobium oxide, an indium tin oxide, copper oxide, nickel oxide, vanadium oxide, chromium oxide, indium oxide, tin oxide, gallium oxide, manganese oxide, iron oxide, cobalt oxide, aluminum oxide, thallium oxide, silicon oxide, germanium oxide, lead oxide, zirconium oxide, molybdenum oxide, hafnium oxide, tantalum oxide, tungsten oxide, cadmium oxide, iridium oxide, rhodium oxide, ruthenium oxide, and osmium oxide,
wherein the electroluminescent quantum dots comprise a core comprising a first semiconductor material and an outer shell surrounding the core, the outer shell comprising a second semiconductor material, wherein the absolute value of the difference between Econduction band edge of the first semiconductor material included in the quantum dot core and Econduction band edge of the second semiconductor material included in the outer shell of the quantum dot is less than the absolute value of the difference between E valence band edge of the first semiconductor material and Evalence band edge of the second semiconductor material, wherein the differences are calculated based on the Econduction band edge and Evalence band edge values for bulk forms of the first and second semiconductor materials measured relative to vacuum level with an energy level=0 eV,
wherein the quantum dots emit light when voltage is applied across the anode and cathode, and wherein the device has a peak EQE of at least 18% when measured over a voltage range from 1 V to 10 V.

### Claim 26 (depends on 25)

A light-emitting device in accordance with claim 25 wherein the nanoparticles of a first inorganic semiconductor material have an average particle size less than 20 nm.

### Claim 27 (depends on 25)

A light-emitting device in accordance with claim 25 wherein the nanoparticles of a first inorganic semiconductor material have an average particle size less than 10 nm.

### Claim 28 (depends on 25)

A light-emitting device in accordance with claim 25 wherein the nanoparticles of a first inorganic semiconductor material have an average particle in a range from about 2 to about 6 nm.