CN110416421B - Quantum dot film and quantum dot light-emitting diode - Google Patents
Quantum dot film and quantum dot light-emitting diode Download PDFInfo
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Abstract
The invention discloses a quantum dot film and a quantum dot light-emitting diode, wherein the quantum dot film comprises cadmium-free quantum dots and interval quantum dots dispersed among the cadmium-free quantum dots; the cadmium-free quantum dots are cadmium-free quantum dots with core-shell structures, and metal elements forming the interval quantum dot material and metal elements forming a shell layer material of the cadmium-free quantum dots are positioned in the same group; the non-metallic elements forming the material of the spaced quantum dots and the non-metallic elements forming the material of the shell layer of the cadmium-free quantum dots are in the same group.
Description
Technical Field
The invention relates to the field of quantum dot light-emitting devices, in particular to a quantum dot film and a quantum dot light-emitting diode.
Background
The quantum dot is a special material which is limited to the nanometer order of magnitude in three dimensions, and the remarkable quantum confinement effect enables the quantum dot to have a plurality of unique nanometer properties: the emission wavelength is continuously adjustable, the light-emitting wavelength is narrow, the absorption spectrum is wide, the light-emitting intensity is high, the fluorescence lifetime is long, the biocompatibility is good, and the like. The characteristics enable the quantum dots to have wide application prospects in the fields of biomarkers, flat panel display, solid-state lighting, photovoltaic solar energy and the like.
In a semiconductor quantum dot material system in the photoelectric field, the cadmium-free quantum dot has the characteristics of environmental protection and green due to the excellent luminescence property of the quantum dot and the fact that the cadmium-free quantum dot does not contain heavy metal cadmium (Cd). However, in the comparison of very important indexes in photoelectric applications such as luminous efficiency and luminous purity (i.e. luminous peak width), the performance of the cadmium-free quantum dots will still significantly lag behind that of the classical cadmium-containing quantum dot system (such as CdSe). The preparation of the cadmium-free quantum dot generally adopts a metallorganic thermal decomposition thermal injection method similar to the cadmium-containing quantum dot, and also adopts a core-shell structure to improve the luminous efficiency and the material stability of the cadmium-free quantum dot on the structural design of the quantum dot.
In the currently widely adopted cadmium-free quantum dot core-shell structure, ZnS, ZnSe or an alloyed structure ZnSeS of ZnSeS and ZnSeS are mainly adopted as a shell structure, but because the shell structure of the components has obvious lattice mismatch with a cadmium-free quantum dot core (such as InP), and because the lattice mismatch cannot be reduced by a method of alloying the core shell due to the inconsistency of the crystal structures, the thickness of the shell layer for realizing better quantum dot performance is smaller than that of a cadmium-containing quantum dot, the particle size of the whole cadmium-free quantum dot core-shell structure is generally about 4-5 nanometers, and the particle size of the cadmium-containing quantum dot used in the quantum dot display technology at present is generally more than 8 nanometers.
The thin shell layer of the cadmium-free quantum dot core-shell structure and the characteristic of small particle size can cause the quantum dots to form a solid film, and then the fluorescence Energy resonance Transfer (FRET) is caused by the interaction between the strong quantum dots, so that the luminous efficiency of the film is remarkably reduced, and as mentioned above, the luminous efficiency of the quantum dots is greatly reduced by increasing the thickness of the shell layer and further increasing the whole particle size. The low luminous efficiency of such a thin film of cadmium-free quantum dots thus also contributes to the low efficiency of the corresponding QLED device.
Therefore, the existing cadmium-free quantum dot thin film and the corresponding structure of the QLED device have disadvantages and problems, and further improvement is needed.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a quantum dot thin film and a quantum dot light emitting diode, which aims to solve the problems that the light emitting efficiency of the existing cadmium-free quantum dot thin film is greatly reduced due to the severe FRET effect caused by the strong interaction, and the light emitting efficiency of the corresponding quantum dot light emitting diode is also greatly reduced.
The technical scheme of the invention is as follows:
a quantum dot film comprising cadmium-free quantum dots and spacer quantum dots dispersed between the cadmium-free quantum dots;
the cadmium-free quantum dots are of a core-shell structure;
the metal elements forming the interval quantum dot material and the metal elements forming the shell layer material of the cadmium-free quantum dot are in the same group; the non-metallic elements forming the material of the spaced quantum dots and the non-metallic elements forming the material of the shell layer of the cadmium-free quantum dots are in the same group.
The quantum dot light-emitting diode comprises a quantum dot light-emitting layer, wherein the quantum dot light-emitting layer is the quantum dot film.
Has the advantages that: by adding the interval quantum dots, the distance between the cadmium-free quantum dots can be effectively increased, so that the interaction between the cadmium-free quantum dots and the FRET effect generated by the cadmium-free quantum dots are effectively weakened, and the luminous efficiency of the quantum dot film is improved; the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials is obviously different from the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials, the spacing quantum dots adopt a structure which is the same as or similar to the cadmium-free quantum dot shell layer, the consistency and the continuity of the whole quantum dot film on the energy level can be ensured, namely the spacing quantum dots can still provide effective energy level constraint on the cadmium-free quantum dots, the energy level constraint effect of the original shell layer of the cadmium-free quantum dots is extended, and extra lattice mismatch is not introduced; the interval quantum dots with wide energy band gaps can realize energy transfer to the cadmium-free luminescent quantum dots, and fully utilize charges injected into the quantum dot layer and generated excitons; in addition, the spacer quantum dots with wide band gaps, i.e., high-energy photons, can realize energy transfer to the cadmium-free quantum dots, and make full use of the charges injected into the quantum dot layer and the generated excitons; and finally, the interval quantum dots can effectively fill gaps formed when the film is formed, so that the quantum dot film with flatness and good compactness is realized.
Drawings
Fig. 1 is a schematic structural diagram of a quantum dot thin film provided by the present invention.
Fig. 2 is a schematic structural diagram of a quantum dot light-emitting diode including a hole injection layer, a hole transport layer, and an electron transport layer according to the present invention.
Fig. 3 is a schematic structural diagram of a quantum dot light-emitting diode in embodiment 7 of the present invention.
Fig. 4 is a schematic structural diagram of a quantum dot light-emitting diode in embodiment 8 of the present invention.
Fig. 5 is a schematic structural diagram of a quantum dot light-emitting diode in embodiment 9 of the present invention.
Detailed Description
The present invention provides a quantum dot thin film and a quantum dot light emitting diode, and the present invention will be described in further detail below in order to make the objects, technical solutions, and effects of the present invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a quantum dot film, which comprises cadmium-free quantum dots 1 and spacing quantum dots 2 dispersed among the cadmium-free quantum dots 1, as shown in figure 1. That is, the quantum dots 1 without cadmium and the spacer quantum dots 2 are uniformly dispersed in the quantum dot thin film. The cadmium-free quantum dots 1 are cadmium-free quantum dots with core-shell structures; the metal elements forming the material of the interval quantum dots 2 and the metal elements forming the material of the shell layer of the cadmium-free quantum dots 1 are in the same group; the non-metallic elements forming the material of the interval quantum dots 2 and the non-metallic elements forming the material of the shell layer of the cadmium-free quantum dots 1 are in the same group. It should be noted that the metal element constituting the spacer quantum dot material and the metal element constituting the shell material of the cadmium-free quantum dot may be the same metal element in the same group, or may be two different metal elements in the same group. The non-metallic elements forming the interval quantum dot material and the non-metallic elements forming the shell layer material of the cadmium-free quantum dot can be the same non-metallic element in the same group, and can also be two different non-metallic elements in the same group.
In a preferred embodiment, the material of the spacer quantum dots and the shell material of the cadmium-free quantum dots are both group II-VI semiconductor materials. Further in a preferred embodiment, the spacer quantum dots are single-core structure quantum dots, because the spacer quantum dots of the core-shell structure can generate self-luminescence and the core-shell structure can easily restrain charge loss, and the material of the spacer quantum dots and the shell material of the cadmium-free quantum dots are selected from one of ZnSe, ZnS, ZnTe, ZnSeS, ZnSeTe and ZnSTe. In a preferred embodiment, the material of the spacer quantum dots and the shell material of the cadmium-free quantum dots are selected from one of ZnS, ZnSe and ZnSeS s.
It should be noted that the material of the spaced quantum dots and the shell material of the cadmium-free quantum dots may be the same semiconductor material in the II-VI group semiconductor materials (i.e., the spaced quantum dots and the shell of the cadmium-free quantum dots have the same material composition), or may be two different semiconductor materials in the II-VI group semiconductor materials (i.e., the spaced quantum dots and the shell of the cadmium-free quantum dots have similar material compositions). For example, when the shell of the cadmium-free quantum dot is ZnSe in a II-VI semiconductor material, the spacing quantum dot may adopt ZnSe in the II-VI semiconductor material, that is, the spacing quantum dot adopts the same material composition as the shell of the cadmium-free quantum dot; when the shell of the cadmium-free quantum dot is ZnSe in a II-VI semiconductor material, the spacing quantum dot can also adopt ZnS or ZnSeS and the like in the II-VI semiconductor material, namely the spacing quantum dot is made of a material similar to the shell of the cadmium-free quantum dot.
Aiming at the problem that the luminous efficiency of the traditional cadmium-free quantum dot film is greatly reduced due to the severe FRET effect caused by the strong interaction of the cadmium-free quantum dots, the quantum dot film is improved, and the distance between the cadmium-free quantum dots can be effectively increased by adding the interval quantum dots, so that the interaction between the cadmium-free quantum dots and the FRET effect generated by the cadmium-free quantum dots are effectively weakened, and the luminous efficiency of the quantum dot film is improved; the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials is obviously different from the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials, the spacing quantum dots adopt a structure which is the same as or similar to the cadmium-free quantum dot shell layer, the consistency and the continuity of the whole quantum dot film on the energy level can be ensured, namely the spacing quantum dots can still provide effective energy level constraint on the cadmium-free quantum dots, the energy level constraint effect of the original shell layer of the cadmium-free quantum dots is extended, and extra lattice mismatch is not introduced; the interval quantum dots with wide energy band gaps can realize energy transfer to the cadmium-free luminescent quantum dots, and fully utilize charges injected into the quantum dot layer and generated excitons; in addition, the spacer quantum dots with wide band gaps, i.e., high-energy photons, can realize energy transfer to the cadmium-free quantum dots, and make full use of the charges injected into the quantum dot layer and the generated excitons; and finally, the interval quantum dots can effectively fill gaps formed when the film is formed, so that the quantum dot film with flatness and good compactness is realized.
The cadmium-free quantum dot is a cadmium-free quantum dot with a core-shell structure, and the core-shell structure can improve the luminous efficiency and the material stability of the cadmium-free quantum dot. In a preferred embodiment, the cadmium-free quantum dot core material is a group III-V semiconductor material. By way of example, the III-V semiconductor material is selected from one of GaN, GaP, GaAs, InP, InAs, InAsP, GaAsP, InGaP, InGaAs, InGaAsP, and the like.
In a preferred embodiment, the spacer quantum dots have a particle size of 2-5 nm. By adjusting the particle size of the interval quantum dots, the luminous efficiency of the quantum dot film can be improved.
In a preferred embodiment, the cadmium-free quantum dots have a particle size of 3 to 6 nm.
In a preferred embodiment, the molar ratio of the cadmium-free quantum dots to the spacer quantum dots in the quantum dot thin film is (1: 0.5) - (1: 4). By adjusting the mixing ratio of the two quantum dots, the luminous efficiency of the quantum dot film can be improved.
In a preferred embodiment, the thickness of the quantum dot thin film is 10 to 80 nm.
The invention also provides a preparation method of the quantum dot film, which comprises the following steps: firstly, mixing cadmium-free quantum dots and interval quantum dots in a nonpolar organic solvent, and uniformly mixing to obtain a mixed quantum dot solution; then preparing the mixed quantum dot solution into a quantum dot film by a solution method; the cadmium-free quantum dots are of a core-shell structure, and metal elements forming the interval quantum dot material and metal elements forming a shell layer material of the cadmium-free quantum dots are in the same group; the non-metallic elements forming the material of the spaced quantum dots and the non-metallic elements forming the material of the shell layer of the cadmium-free quantum dots are in the same group.
The solution method of the present invention may be a spin coating method, an ink jet printing method, etc., without being limited thereto. As an example, the non-polar organic solvent may be selected from chloroform, toluene, chlorobenzene, n-hexane, n-octane, decalin, tridecane, and the like, without being limited to one of them.
The invention also provides a quantum dot light-emitting diode which comprises a quantum dot light-emitting layer, wherein the quantum dot light-emitting layer is the quantum dot film. In a preferred embodiment, the thickness of the quantum dot thin film is 10 to 80 nm.
The quantum dot light emitting diode in the prior art has various forms, and the invention will be mainly described by taking the quantum dot light emitting diode as shown in fig. 2 as an example. Specifically, as shown in fig. 2, the quantum dot light emitting diode includes a substrate, a transparent conductive anode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer, and a cathode, which are stacked from bottom to top. The quantum dot light-emitting layer is the quantum dot film.
In a preferred embodiment, the thickness of the quantum dot light emitting layer is 10 to 80 nm. The quantum dot light-emitting diode has higher luminous efficiency under the thickness.
In a preferred embodiment, the substrate may be glass, PET, PI, or the like, but is not limited thereto.
In a preferred embodiment, the transparent conductive anode may be selected from one or more of indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), antimony doped tin oxide (ATO), aluminum doped zinc oxide (AZO).
In a preferred embodiment, the material of the hole injection layer may be selected from materials having good hole injection properties, such as but not limited to poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazatriphenylene (HATCN), doped or undoped, and the likeOne or more of transition metal oxides, doped or undoped metal chalcogenide compounds; wherein the transition metal oxide includes, but is not limited to, MoO3、VO2、WO3One or more of CuO and CuO; the metal chalcogenide compounds include but are not limited to MoS2、MoSe2、WS2、WSe2And CuS. In a preferred embodiment, the hole injection layer has a thickness of 10 to 150 nm.
In a preferred embodiment, the material of the hole transport layer may be selected from organic materials having good hole transport ability, such as but not limited to Poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), Polyvinylcarbazole (PVK), Poly (N, N ' bis (4-butylphenyl) -N, N ' -bis (phenyl) benzidine) (Poly-TPD), Poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4', 4 "-tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N ' -diphenyl-N, one or more of N ' -bis (3-methylphenyl) -1,1 ' -biphenyl-4, 4' -diamine (TPD), N ' -diphenyl-N, N ' - (1-naphthyl) -1,1 ' -biphenyl-4, 4' -diamine (NPB), doped graphene, undoped graphene, C60. In a preferred embodiment, the hole transport layer has a thickness of 10 to 150 nm.
In a preferred embodiment, the material of the electron transport layer may be selected from materials with good electron transport properties, such as, but not limited to, ZnO, TiO, which may be n-type2、Fe2O3、SnO2、Ta2O3One or more of AlZnO, ZnSnO, InSnO and the like. In a further preferred embodiment, the material of the electron transport layer is selected from n-type ZnO and n-type TiO2One kind of (1). In a preferred embodiment, the thickness of the electron transport layer is 10 to 150 nm.
In a preferred embodiment, the cathode may be selected from one of an aluminum (Al) electrode, a silver (Ag) electrode, and a gold (Au) electrode. In a preferred embodiment, the cathode has a thickness of 30 to 800 nm.
The invention also provides a preparation method of the quantum dot light-emitting diode, which comprises the following steps:
providing a substrate, and forming a transparent conductive anode on the substrate;
depositing a hole injection layer, a hole transport layer, a quantum dot light emitting layer and an electron transport layer on the transparent conductive anode in sequence; wherein the quantum dot light-emitting layer is the quantum dot film;
and (3) evaporating and plating a cathode on the electron transmission layer to prepare the quantum dot light-emitting diode.
In the present invention, each layer deposition method may be a chemical method or a physical method, wherein the chemical method includes, but is not limited to, one or more of a chemical vapor deposition method, a successive ionic layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method, a coprecipitation method; the physical method includes, but is not limited to, one or more of spin coating, printing, knife coating, dip coating, dipping, spraying, roll coating, casting, slit coating, bar coating, thermal evaporation, electron beam evaporation, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition.
The present invention will be described in detail below with reference to examples.
Example 1: pure quantum dot film of InP/ZnS cadmium-free quantum dot (comparison group)
(1) Selecting InP/ZnS cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnS cadmium-free quantum dots have a luminescence peak wavelength of 520nm, a particle size of 4.6nm and a solution quantum yield of 62%;
(2) adding InP/ZnS cadmium-free quantum dots into a normal octane solution, and fully and uniformly mixing to form a quantum dot solution with the mass concentration of 30 mg/mL;
(3) forming a thin film from the quantum dot solution in a spin coating mode;
(4) the quantum yield of the film was 17%.
Example 2: quantum dot film of InP/ZnS cadmium-free quantum dots and ZnS quantum dots (small particle size)
(1) Selecting InP/ZnS cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnS cadmium-free quantum dots have a luminescence peak wavelength of 520nm, a particle size of 4.6nm and a solution quantum yield of 62%;
(2) ZnS oil phase quantum dots with the particle size of 2.1nm are selected as spacing quantum dots;
(3) adding InP/ZnS cadmium-free quantum dots and ZnS spacer quantum dots into an n-octane solution in a molar ratio of 1:2, and fully and uniformly mixing to form a mixed quantum dot solution with the mass concentration of 30 mg/mL;
(4) forming a thin film by the mixed quantum dot solution in a spin coating mode;
(5) the quantum yield of the film was determined to be 34%.
Example 3: quantum dot thin film of InP/ZnS cadmium-free quantum dots and ZnS quantum dots (large particle size)
(1) Selecting InP/ZnS cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnS cadmium-free quantum dots have a luminescence peak wavelength of 520nm, a particle size of 4.6nm and a solution quantum yield of 62%;
(2) ZnS oil phase quantum dots with the particle size of 4.7nm are selected as spacing quantum dots;
(3) adding InP/ZnS cadmium-free quantum dots and ZnS spacer quantum dots into an n-octane solution in a molar ratio of 1:2, and fully and uniformly mixing to form a mixed quantum dot solution with the mass concentration of 30 mg/mL;
(4) forming a thin film by the mixed quantum dot solution in a spin coating mode;
(5) the quantum yield of the film was 14%. Comparing the results of examples 1 and 2 shows that when the selected spacer quantum dots have larger particle sizes, the mixing ratio of the spacer quantum dots and the cadmium-free quantum dots is not too high.
Example 4: quantum dot thin film of InP/ZnS cadmium-free quantum dots and ZnS quantum dots (large particle size)
(1) Selecting InP/ZnS cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnS cadmium-free quantum dots have a luminescence peak wavelength of 520nm, a particle size of 4.6nm and a solution quantum yield of 62%;
(2) ZnS oil phase quantum dots with the particle size of 4.7nm are selected as spacing quantum dots;
(3) adding InP/ZnS cadmium-free quantum dots and ZnS spacer quantum dots into an n-octane solution in a molar ratio of 1:0.8, and fully and uniformly mixing to form a mixed quantum dot solution with the mass concentration of 30 mg/mL;
(4) forming a thin film by the mixed quantum dot solution in a spin coating mode;
(5) the quantum yield of the film was measured to be 25%. Compared with the result of the embodiment 3, the result shows that when the particle size of the selected interval quantum dot is larger, the luminous efficiency of the quantum dot film can be improved by adjusting the mixing ratio of the two quantum dots.
Example 5: quantum dot film of InP/ZnSe cadmium-free quantum dot and ZnSe quantum dot
(1) Selecting InP/ZnSe cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnSe cadmium-free quantum dots have a luminescence peak wavelength of 613nm, a particle size of 5.1nm and a solution quantum yield of 57%;
(2) ZnSe oil phase quantum dots with the particle size of 3.6nm are selected as spacing quantum dots;
(3) adding the InP/ZnSe cadmium-free quantum dots and the ZnSe spacer quantum dots into an n-octane solution according to the molar ratio of 1:1, and fully and uniformly mixing to form a mixed quantum dot solution with the mass concentration of 30 mg/mL;
(4) forming a thin film by the mixed quantum dot solution in a spin coating mode;
(5) the quantum yield of the film was 31%.
Example 6: quantum dot film of InP/ZnSe cadmium-free quantum dot and ZnS quantum dot
(1) Selecting InP/ZnSe cadmium-free quantum dots with a core-shell structure, wherein the InP/ZnSe cadmium-free quantum dots have a luminescence peak wavelength of 613nm, a particle size of 5.1nm and a solution quantum yield of 57%;
(2) ZnS oil phase quantum dots with the particle size of 2.1nm are selected as spacing quantum dots;
(3) adding InP/ZnSe cadmium-free quantum dots and ZnS spacer quantum dots into an n-octane solution in a molar ratio of 1:1.5, and fully and uniformly mixing to form a mixed quantum dot solution with the mass concentration of 30 mg/mL;
(4) forming a thin film by the mixed quantum dot solution in a spin coating mode;
(5) the quantum yield of the film was measured to be 35%.
Example 7: positive bottom emission quantum dot light-emitting diode
The quantum dot light emitting diode of the embodiment, as shown in fig. 3, sequentially includes from bottom to top: ITO substrate 11, bottom electrode 12, PEDOT: PSS hole injection layer 13, poly-TPD hole transport layer 14, quantum dot light emitting layer 15, ZnO electron transport layer 16 and Al top electrode 17.
The preparation steps of the quantum dot light-emitting diode are as follows:
a bottom electrode 12, a 30nm PEDOT: after the PSS hole injection layer 13 and the 30nm poly-TPD hole transport layer 14, a quantum dot light emitting layer 15 with the thickness of 20nm is prepared on the poly-TPD hole transport layer 14, and then a 40nm ZnO electron transport layer 16 and a 100nm Al top electrode 17 are sequentially prepared on the quantum dot light emitting layer 15. The quantum dot light-emitting layer 15 is a quantum dot thin film as described in example 2.
Example 8: positive bottom emission quantum dot light-emitting diode
In this embodiment, the quantum dot light emitting diode, as shown in fig. 4, sequentially includes from bottom to top: ITO substrate 21, bottom electrode 22, PEDOT: PSS hole injection layer 23, Poly (9-vinylcarbazole) (PVK) hole transport layer 24, quantum dot light emitting layer 25, ZnO electron transport layer 26 and Al top electrode 27.
The preparation steps of the quantum dot light-emitting diode are as follows:
a bottom electrode 22, a 30nm PEDOT: after the PSS hole injection layer 23 and the 30nm PVK hole transport layer 24, a quantum dot light emitting layer 25 with the thickness of 20nm is prepared on the PVK hole transport layer 24, and then a 40nm ZnO electron transport layer 26 and a 100nm Al top electrode 27 are sequentially prepared on the quantum dot light emitting layer 25. The quantum dot light-emitting layer 25 is a quantum dot thin film as described in example 4.
Example 9: positive bottom emission quantum dot light-emitting diode
The quantum dot light emitting diode of the embodiment, as shown in fig. 5, sequentially includes from bottom to top: ITO substrate 31, bottom electrode 32, PEDOT: PSS hole injection layer 33, poly-TPD hole transport layer 34, quantum dot light emitting layer 35, TPBi electron transport layer 36, and Al top electrode 37.
The preparation steps of the quantum dot light-emitting diode are as follows:
a bottom electrode 32, a 30nm PEDOT: after the PSS hole injection layer 33 and the 30nm poly-TPD hole transport layer 34, a quantum dot light emitting layer 35 with the thickness of 20nm is prepared on the poly-TPD hole transport layer 34, and then a 30nm TPBi electron transport layer 36 and a 100nm Al top electrode 37 are sequentially prepared on the quantum dot light emitting layer 35 through a vacuum evaporation method. The quantum dot light-emitting layer 35 is a quantum dot thin film as described in example 5.
In conclusion, the distance between the cadmium-free quantum dots can be effectively increased by adding the spacing quantum dots, so that the interaction between the cadmium-free quantum dots and the FRET effect generated by the interaction are effectively weakened, and the luminous efficiency of the cadmium-free quantum dot film is improved; the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials is obviously different from the mode that the distance between the cadmium-free quantum dots is increased by adding other spacing materials, the spacing quantum dots adopt a structure which is the same as or similar to the cadmium-free quantum dot shell layer, the consistency and the continuity of the whole quantum dot film on the energy level can be ensured, namely the spacing quantum dots can still provide effective energy level constraint on the cadmium-free quantum dots, the energy level constraint effect of the original shell layer of the cadmium-free quantum dots is extended, and extra lattice mismatch is not introduced; in addition, the spacer quantum dots with wide band gaps, i.e., high-energy photons, can realize energy transfer to the cadmium-free quantum dots, and make full use of the charges injected into the quantum dot layer and the generated excitons; and finally, the interval quantum dots can effectively fill gaps formed when the film is formed, so that the quantum dot film with flatness and good compactness is realized.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (7)
1. A quantum dot film, comprising cadmium-free quantum dots and spacer quantum dots dispersed between the cadmium-free quantum dots;
the cadmium-free quantum dots are of a core-shell structure;
the metal elements forming the interval quantum dot material and the metal elements forming the shell layer material of the cadmium-free quantum dot are in the same group; the non-metallic elements forming the material of the interval quantum dots and the non-metallic elements forming the material of the shell layer of the cadmium-free quantum dots are in the same group;
the material of the interval quantum dots and the shell material of the cadmium-free quantum dots are selected from one of ZnTe, ZnSeS, ZnSeTe and ZnSTe;
the particle size of the interval quantum dots is 2-5nm, and the particle size of the cadmium-free quantum dots is 3-6 nm.
2. The quantum dot thin film of claim 1, wherein the cadmium-free quantum dot core material is a group III-V semiconductor material.
3. The quantum dot film of claim 2, wherein the group III-V semiconductor material is selected from one of GaN, GaP, GaAs, InP, InAs, InAsP, GaAsP, InGaP, InGaAs, and InGaAsP.
4. The quantum dot film of claim 1, wherein the cadmium-free quantum dots and the spacer quantum dots are mixed in the quantum dot film at a molar ratio of 1:0.5-1: 4.
5. The quantum dot thin film of claim 1, wherein the quantum dot thin film has a thickness of 10-80 nm.
6. A quantum dot light-emitting diode comprising a quantum dot light-emitting layer, wherein the quantum dot light-emitting layer is the quantum dot thin film according to any one of claims 1 to 5.
7. The quantum dot light-emitting diode of claim 6, wherein the quantum dot thin film has a thickness of 10-80 nm.
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| CN113130794B (en) * | 2019-12-31 | 2022-12-13 | Tcl科技集团股份有限公司 | Quantum dot light-emitting diode and preparation method thereof |
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| CN106384767A (en) * | 2016-11-18 | 2017-02-08 | Tcl集团股份有限公司 | Quantum dot LED, manufacturing method thereof, light emitting module group and display apparatus |
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| CN105609651A (en) * | 2016-01-07 | 2016-05-25 | 东南大学 | High-efficiency quantum dot light emitting diode with self-assembly polymer hole transmission layer structure |
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