Light-emitting element, display device, and method for manufacturing light-emitting element

Abstract

A light-emitting element (7) according to the present disclosure is provided with: a light-emitting layer (5) that is disposed between an anode (EA) and a cathode (EC) and contains a plurality of quantum dots (QD) and an inorganic host material (MX) filled between the plurality of quantum dots (QD); and a functional layer (6F) disposed between the anode (EA) and the cathode (EC) so as to be adjacent to the light-emitting layer (5), the functional layer (6F) having the same constituent element as the inorganic matrix material (MX) and having a different composition ratio.

Description

Technical Field

[0001] The present disclosure relates to a light emitting element, a display device, and a method for manufacturing the light emitting element. Background Art

[0002] In a light-emitting element having a light-emitting layer containing quantum dots as a light-emitting material, there is a situation where carriers are not injected into the quantum dots and invalid current is generated through the light-emitting layer. In addition to reducing the luminous power efficiency of the light-emitting element, the generation of this invalid current also causes the quantum dots and the charge transport layer to deteriorate, resulting in a problem of reduced reliability of the light-emitting element. Patent document 1 discloses a light-emitting element, wherein the light-emitting layer includes a plurality of quantum dots with different shell film thicknesses, thereby improving the confinement of carriers to the quantum dots. Prior art literature Patent Literature

[0003] Patent Document 1: International Publication No. WO2015 / 056750 Summary of the invention Technical Problems to be Solved by the Invention

[0004] In the light-emitting element disclosed in Patent Document 1, since organic ligands exist between quantum dots, it is difficult to reduce ineffective current flowing between quantum dots to improve light-emitting power efficiency. In addition, degradation of the organic ligands causes a problem of reduced reliability. Technical solutions for solving technical problems

[0005] One aspect of the present disclosure involves a light-emitting element comprising: an anode and a cathode; a light-emitting layer, which is arranged between the anode and the cathode and contains an inorganic matrix material filled with multiple quantum dots and between the multiple quantum dots; and a functional layer, which is arranged between the anode and the cathode in a manner adjacent to the light-emitting layer, and its constituent elements are the same as those of the inorganic matrix material but have a different composition ratio. Beneficial Effects

[0006] According to one embodiment of the present disclosure, the light emitting power efficiency of a light emitting element can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a cross-sectional view showing the structure of a light emitting element according to an embodiment. Figure 2 yes Figure 1 An example of a schematic energy band diagram of a light-emitting element is shown. Figure 3 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Figure 4 yes Figure 3 An example of a schematic energy band diagram of a light-emitting element is shown. Figure 5 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Figure 6 yes Figure 5 An example of a schematic energy band diagram of a light-emitting element is shown. Figure 7 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Figure 8 yes Figure 7 An example of a schematic energy band diagram of a light-emitting element is shown. Fig. 9 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Fig.10 yes Fig. 9 An example of a schematic energy band diagram of a light-emitting element is shown. Fig.11 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Fig.12 yes Fig.11 An example of a schematic energy band diagram of a light-emitting element is shown. Fig.13 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Fig.14 1 is a flowchart showing a method for manufacturing a light emitting element according to an embodiment. Fig.15 It is a schematic cross-sectional view showing a method for forming a functional layer using the CBD method. Fig.16A It is a schematic cross-sectional view showing an example of formation of an inorganic substrate. Fig. 16B It is a schematic cross-sectional view showing an example of formation of an inorganic substrate. Fig.17 This is a schematic diagram showing an example of the configuration of the display device according to this embodiment. Fig.18 This is a cross-sectional view showing an example of the configuration of the display device according to this embodiment. DETAILED DESCRIPTION

[0008] [Implementation method 1] (Constitution of Light Emitting Element)

[0009] Figure 1 2 is a cross-sectional view showing the structure of a light emitting element according to an embodiment. Figure 1As shown, the light-emitting element 7 of this embodiment comprises: an anode EA and a cathode EC; a light-emitting layer 5, which is arranged between the anode EA and the cathode EC and comprises a plurality of quantum dots QD and an inorganic matrix material MX filling the spaces between the plurality of quantum dots QD; and a functional layer 6F, which is arranged between the anode EA and the cathode EC in a manner adjacent to the light-emitting layer 5, and whose constituent elements are the same as those of the inorganic matrix material MX but have a different composition ratio. The functional layer 6F and the inorganic matrix material MX may be sulfide metals of the same crystal form. The functional layer 6F may also be an electron transport layer (ETL) arranged between the cathode EC and the light-emitting layer 5. A hole transport layer (HTL) 4 may be arranged between the anode EA and the light-emitting layer 5.

[0010] In the light-emitting element 7, since the inorganic matrix MX and the functional layer 6F having the same constituent elements are homogeneously bonded, the potential barrier between the functional layer 6F and the inorganic matrix MX becomes small. Therefore, charge injection (e.g., electron injection) from the functional layer 6F to the light-emitting layer 5 becomes easy, and the light-emitting power efficiency (power consumption-brightness characteristics of the light-emitting element) is improved.

[0011] The inorganic matrix MX caps the surface defects of the quantum dots QD, reducing non-luminescent recombination in the quantum dots QD, thereby improving the external luminous efficiency (EQE). The inorganic matrix MX has better durability than general organic ligands, thereby improving the reliability of the light-emitting element 7.

[0012] In this way, by forming a functional layer 6F having the same compound (same constituent elements) as the inorganic matrix material MX and a different composition adjacent to the light-emitting layer 5, it is possible to use an inorganic matrix material MX (such as zinc sulfide, zinc selenide) that can be formed at a low temperature and has a low defect density while reducing the voltage used for carrier injection.

[0013] Alternatively, each of the plurality of quantum dots QD has a core 8 and a shell 9 whose constituent elements are the same as those of the inorganic matrix material MX. The composition ratio of the inorganic matrix material MX and the shell 9 may be the same or different. In this way, the sealing effect of the shell 9 can be maintained and the luminescence characteristics (voltage-brightness characteristics) can be made low voltage.

[0014] The functional layer 6F and the inorganic matrix material MX may each contain a metal element and a non-metal element, the metal element is zinc, and the non-metal element is sulfur or selenium. The functional layer 6F may contain hydroxyl groups, and the functional layer 6F may contain metal-hydroxyl bonds (details will be described later).

[0015] Figure 2 yes Figure 1An example of a schematic energy band diagram of a light-emitting element shown below. Hereinafter, being close to the vacuum level VE (0 eV) is expressed as "shallow", and being far from the vacuum level VE (0 eV) is expressed as "deep". CBM is the lower energy level of the conduction band, VBM is the upper energy level of the valence band, the band gap is the difference between CBM and VBM, and FE is the Fermi level. As Figure 2 shown, the band gap of the inorganic matrix material MX can be larger than that of a plurality of quantum dots QD. The band gap of the quantum dot QD can be the band gap of the core or the band gap of the shell. When the functional layer 6F is an electron transport layer (ETL) disposed between the light-emitting layer 5 and the cathode EC, the CBM of the functional layer 6F can be shallower than that of a plurality of quantum dots QD and deeper than that of the inorganic matrix material MX. The CBM of the quantum dot QD can be the CBM of the core. In this way, by adjusting the CBM of the functional layer 6F, the amount of electron injection can be adjusted. Since the CBM is shallower than that of the quantum dot QD, the electron injection barrier from the functional layer 6F (electron transport layer) to the light-emitting layer 5 becomes smaller, and the luminous power efficiency is improved. In addition, since the CBM of the functional layer 6F is adjusted to be deeper than the CBM of the inorganic matrix MX, the electron injection into the inorganic matrix MX is suppressed. As a result, the light-emitting region is close to the functional layer 6F, and non-radiative recombination at the interface between the hole transport layer 4 and the light-emitting layer 5 can be suppressed. In Figure 1 and Figure 2 cases, the CBM of the functional layer 6F (ETL) can be deeper than the shell 9 of the quantum dot QD.

[0016] By controlling the Fermi level of the functional layer 6F, a stepped electric potential can be formed, and the voltage for carrier injection (electron injection) can be reduced. The control of the Fermi level can be performed, for example, by controlling the ratio of zinc elements in zinc sulfide and zinc selenide. In the case of an excess of zinc elements, n-type conductivity with sulfur defects and selenium defects as donors is achieved. Therefore, the composition ratio of zinc in the functional layer 6F (ETL) can be larger than that of the inorganic matrix material MX. The functional layer 6F (ETL) can be zinc x sulfide represented by S(x>1), and the inorganic matrix material Mx can be zinc y sulfide represented by S(0<y<x). The functional layer 6F (ETL) can be zinc x selenide represented by Se(x>1), and the inorganic matrix material Mx can be zinc y selenide represented by Se(0<y<x).

[0017] Figure 3 is a cross-sectional view showing another configuration example of the light-emitting element according to the embodiment. Figure 4 is Figure 3 an example of a schematic energy band diagram of the light-emitting element shown. As Figure 3As shown, at least one of the multiple quantum dots QD may also be in contact with the functional layer 6F. That is, the light-emitting layer 5 includes quantum dots QD having a portion exposed from the inorganic matrix material MX, and the exposed portion is in contact with the functional layer 6F. Since the functional layer 6F has a deeper CBM than the inorganic matrix material MX and has a high carrier transport property, the luminescence characteristics (voltage-brightness characteristics) can be made lower voltage. Moreover, since there is no inorganic matrix MX between the exposed quantum dots QD, the electron injection barrier is reduced, which can make the luminescence characteristics (voltage-brightness characteristics) lower voltage. Figure 3 The structure can be formed, for example, by etching the vicinity of the upper surface of the inorganic matrix material MX after forming the light-emitting layer 5 containing the inorganic matrix material MX, so that a part of the quantum dots QD near the upper surface is exposed from the inorganic matrix material MX. As an example, if a CBD (Chemical bath deposition) method is used to grow an inorganic layer (functional layer 6F) using an alkaline aqueous solution, the etching of the inorganic matrix material MX and the growth of the functional layer 6F can be performed in the same process of a simple aqueous solution system. In the functional layer 6F formed by the CBD method, the OH group (hydroxyl group) is bonded to the metal element, thereby capping the unbonded bonds (dangling bonds) of the metal element, thereby suppressing the non-luminescent migration of carriers in the functional layer 6F. Moreover, the mobility, which is one of the indicators of carrier transport characteristics, is very high, and a mobility greater than 1.0 [cm 2 / Vs], so that carrier transport can be performed at a lower voltage.

[0018] Figure 5 It is a cross-sectional view showing another configuration example of the light emitting element according to the embodiment. Figure 6 yes Figure 5 An example of a schematic energy band diagram of a light-emitting element is shown in FIG. Figure 5 as well as Figure 6 As shown, the functional layer 6F is the first electron transport layer, and the second electron transport layer 6S is arranged between the first electron transport layer 6F and the cathode EC. The constituent elements of the second electron transport layer 6S are the same as those of the first electron transport layer 6F, and the composition ratio may be different. The CBM of the second electron transport layer 6S is deeper than the first electron transport layer 6F. By forming the CBM of the first electron transport layer 6F and the second electron transport layer 6S to form a step-shaped potential, the carrier injection voltage to the quantum dot QD can be reduced compared with the case of a single electron transport layer 6F.

[0019] exist Figure 5 as well as Figure 6 In the embodiment, by controlling the Fermi level of the first electron transport layer 6F and the second electron transport layer 6S, a step potential is formed, which can reduce the voltage for carrier injection (electron injection). For example, the first electron transport layer 6F can be made of Znx S (x>1) represents zinc sulfide, and the second electron transport layer 6S can be made of Zn z S (z>x) represents zinc sulfide, the first electron transport layer 6F can be made of Zn x Se (x>1) represents zinc selenide, the second electron transport layer 6S can be made of Zn z Zinc selenide represented by Se(z>x).

[0020] Figure 7 It is a cross-sectional view showing another configuration example of the light emitting element according to the embodiment. Figure 8 yes Figure 7 An example of a schematic energy band diagram of a light-emitting element is shown in FIG. Figure 7 as well as Figure 8 As shown, the functional layer 6F is the first electron transport layer, and the second electron transport layer 6T is arranged between the first electron transport layer 6F and the cathode EC. The electron mobility of the first electron transport layer 6F is set to S1, the thickness is set to Da, and the electron mobility of the second electron transport layer 6T is set to S2, and the thickness is set to Db, then it can also be S1 / Da 3 ≥S2 / Db 3 .

[0021] In order to improve the external luminous efficiency (EQE) of the light-emitting element 7, it is necessary to improve the carrier injection efficiency of electrons and holes injected into the QD. Furthermore, if excessive carriers are generated, they will not contribute to the luminescent recombination. Therefore, it is effective to adjust the carrier balance, which is the ratio of the injected amount of electrons and holes. Figure 7 As shown, by stacking the first electron transport layer 6F and the second electron transport layer 6T having a lower mobility than the first electron transport layer 6F, a bottleneck of the electron injection amount is intentionally created, and the carrier balance can be generally aligned with the hole side where the carrier injection amount is low.

[0022] The carrier injection amount was calculated by solving the Poisson equation taking into account the dielectric constant, mobility, carrier density, and film thickness of the ETL material. 2 / Vs] or less, the space charge limited current (SCLC) is more dominant than the ohmic current, and the carrier injection amount is described based on Child's law with dielectric constant, mobility, film thickness, and voltage as parameters. Here, the dielectric constants of the first electron transport layer 6F and the second electron transport layer 6T are set to be the same. When comparing the electron injection amount under the same voltage, the electron mobility of the first electron transport layer 6F is set to S1 and the thickness is set to Da, the electron mobility of the second electron transport layer 6T is set to S2 and the thickness is set to Db, and S1 / Da 3 ≥S2 / Db 3In this case, the bottleneck of electron injection can be intentionally created, which can improve the carrier balance and thus improve the external luminous efficiency (EQE).

[0023] Fig. 9 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Fig.10 yes Fig. 9 An example of a schematic energy band diagram of a light-emitting element is shown in FIG. Fig. 9 and Fig.10 As shown, a functional layer 4F (hole transport layer: HTL) having the same constituent elements as the inorganic matrix material MX but a different composition ratio may be configured between the light-emitting layer 5 and the anode EA. The VBM of the functional layer 4F may be deeper than that of the plurality of quantum dots QD. The VBM of the functional layer 4F may be shallower than that of the inorganic matrix material MX.

[0024] If zinc sulfide and zinc selenide are insufficient in the atomic composition ratio, they show p-type conductivity with zinc defects as acceptors. Therefore, the zinc composition ratio of the functional layer 4F (HTL) can be smaller than that of the inorganic matrix material MX. The functional layer 4F (HTL) can be composed of Zn x S (x < 1) represents zinc sulfide, and the inorganic matrix material Mx can be Zn y S (0<x<y) represents zinc sulfide, the functional layer 4F (HTL) can be made of Zn x Se(x<1) represents zinc selenide, the inorganic matrix material Mx can be Zn y Zinc selenide represented by Se(0<x<y).

[0025] In the light-emitting element 7, since the inorganic matrix material MX and the functional layer 4F (HTL) having the same constituent elements are homogeneously bonded, the potential barrier between the functional layer 4F and the inorganic matrix material MX becomes smaller. Therefore, hole injection from the functional layer 4F to the light-emitting layer 5 becomes easy, and the light-emitting power efficiency (power consumption-brightness characteristics of the light-emitting element) is improved. In addition, by making the functional layer 4F so that the VBM is deeper than the plurality of quantum dots QD, the hole injection barrier from the functional layer 4F (hole transport layer) to the light-emitting layer 5 becomes smaller, and the light-emitting power efficiency is improved.

[0026] Fig.11 It is a cross-sectional view showing another structure of the light emitting element according to the embodiment. Fig.12 yes Fig.11 An example of a schematic energy band diagram of a light-emitting element is shown in FIG. Fig.11 and Fig.12 As shown, the functional layer 4F is the first hole transport layer, and the second hole transport layer 4S can be configured between the first hole transport layer 4F and the anode EA. The hole mobility of the first hole transport layer 4F is set to S3, the thickness is set to Dc, and the hole mobility of the second hole transport layer 4S is set to S4, and the thickness is set to Dd, which can be S3 / Dc3 ≥S4 / Dd 3 In this way, the bottleneck of hole injection can be actively created, the carrier balance can be improved, and the external luminous efficiency (EQE) can be improved.

[0027] Fig.13 2 is a cross-sectional view showing another configuration example of a light emitting element according to an embodiment of the present invention. Fig.13 As shown, a functional layer 4F (HTL) having the same constituent elements as the inorganic matrix material MX but a different composition ratio may be arranged between the anode EA and the light-emitting layer 5, and a functional layer 6F (ETL) having the same constituent elements as the inorganic matrix material MX but a different composition ratio may be arranged between the cathode EC and the light-emitting layer 5. The inorganic matrix material MX and the functional layers 4F and 6F are zinc chalcogenide (zinc sulfide, zinc selenide, etc.), the zinc composition ratio of the functional layer 6F (ETL) may be greater than that of the inorganic matrix material MX, and the zinc composition ratio of the functional layer 4F (HTL) may be less than that of the inorganic matrix material MX. In this way, the injection barrier caused by the step potential can be reduced for electrons and holes, respectively.

[0028] Fig.14 FIG. 1 is a flow chart showing a method for manufacturing a light-emitting element according to this embodiment. Figure 1 and Fig.14 As shown, the manufacturing method of the light-emitting element of the embodiment includes a step S10 of forming a lower electrode (for example, an anode EA), a step S20 of forming a light-emitting layer 5 including a plurality of quantum dots QD and an inorganic matrix material MX filling the plurality of quantum dots QD, a step S30 of forming a functional layer 6F on the light-emitting layer 5 whose constituent elements are the same as those of the inorganic matrix material MX but have a different composition ratio, and a step S40 of forming an upper electrode (for example, a cathode EC).

[0029] Fig.15 Schematic cross-sectional view showing a method for forming a functional layer using the CBD method. For example, in a state where the bottom surface BF and the side surface SF of the stacked body ST are covered with a mask MK, the stacked body ST formed by stacking a substrate 13, an anode EA, a hole transport layer 4, and a light-emitting layer 5 is immersed in an alkaline aqueous solution 10 containing a metal source and a chalcogen element at a predetermined temperature for a predetermined time, so that the functional layer 6F can be grown on the stacked body ST (in contact with the light-emitting layer 5).

[0030] For example, by mixing zinc sulfate (ZnSO4) with a concentration of 0.16 mol / L as a zinc source, ammonia with a concentration of 7.5 mol / L as an alkali source, and thiourea with a concentration of 0.6 mol / L as a sulfur source, an alkaline aqueous solution 10 with a pH of 11 is obtained. The alkaline aqueous solution 10 is adjusted to 80° C., and the laminate ST is immersed for 15 minutes, thereby forming a zinc sulfide thin film (containing oxygen atoms and hydroxyl groups) with a film thickness of 100 nm.

[0031] The quantum dot QD used in this embodiment can be a point with a maximum width of less than 100 [nm], and the shape can be spherical or non-spherical. The shape of the quantum dot QD is not particularly limited as long as it satisfies the above-mentioned maximum width, and is not limited to a sphere (circular cross-sectional shape). The maximum width can be greater than 1.0 [nm]. For example, the shape can be a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branch-shaped three-dimensional shape, a three-dimensional shape with concave and convex surfaces on the surface, or a combination of these shapes. The quantum dot QD can be composed of a semiconductor material or an inorganic semiconductor nanocrystal. The semiconductor material can have a certain band gap or can be a material that produces electroluminescence. The wavelength region of electroluminescence can be any one of the red region, the green region, and the blue region.

[0032] Quantum dots QD may have any one of II-VI semiconductor crystals such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, and / or III-V semiconductor crystals such as GaAs, GaP, InN, In-As, InP, InSb, and / or IV semiconductor crystals such as Si and Ge. In addition, II-VI compounds refer to compounds containing II group elements and VI group elements, and III-V compounds refer to compounds containing III group elements and V group elements. In addition, II group elements include Group 2 elements and Group 12 elements, Group III elements include Group 3 elements and Group 13 elements, Group V elements include Group 5 elements and Group 15 elements, and Group VI elements may include Group 6 elements and Group 16 elements.

[0033] Chalcogenides are compounds containing elements of Group VIA (16), such as CdS or CdSe. Chalcogenides may also contain mixed crystals of these.

[0034] The perovskite compound has a composition represented by the general formula CsPbX3, for example. The constituent element X includes at least one selected from the group consisting of Cl, Br, and I, for example.

[0035] Here, element group numbering using Roman numerals is based on the old IUPAC (International Union of Pure and Applied Chemistry) method or the old CAS (Chemical Abstracts Service) method, and element group numbering using Arabic numerals is based on the current IUPAC method.

[0036] Fig.16A and Fig. 16B Schematic cross-sectional view showing an example of forming an inorganic substrate. Fig.16A and Fig. 16B As shown, the inorganic matrix material MX satisfies the region (space) JS between two adjacent quantum dots QD, and the inorganic matrix material MX fills the region JS. The region JS can be the region surrounded by two straight lines (common tangent lines) tangent to the periphery of two adjacent quantum dots QD in the cross section of the light-emitting layer 5 and the two adjacent quantum dots QD. In addition, as Fig. 16B As shown, even if two adjacent quantum dots are close, region JS exists, and the inorganic matrix material MX satisfies region JS. The so-called inorganic matrix material filling between multiple quantum dots is sufficient as long as the inorganic matrix material is filled between at least two quantum dots QD. That is, if it is known that the region (space) JS between two adjacent quantum dots QD satisfies the inorganic matrix material MX, it can be said that the inorganic matrix material MX is satisfied between multiple quantum dots QD. In addition, as an example different from "filling" or "filling", sometimes there is a case of "supporting", where two adjacent quantum dots QD can be supported by the presence of an inorganic matrix material MX in the region JS, or two quantum dots QD can be supported by, for example, at least a portion of the region JS being filled with an inorganic matrix MX.

[0037] The inorganic matrix material MX has inorganic materials (inorganic substances) as the main component. The inorganic matrix material Mx can also be a constituent element of the light-emitting layer containing multiple quantum dots QD. The inorganic matrix material MX can be a component composed of an inorganic substance (such as an inorganic semiconductor) that contains and maintains other substances, and can be called a substrate, a mother material or a filling material. The inorganic matrix material Mx can also be solid at room temperature. The inorganic matrix material Mx can also contain multiple quantum dots QD. The inorganic matrix material MX can satisfy the area (space) other than the multiple quantum dots QD in the light-emitting layer (quantum dot layer), and can also satisfy the multiple quantum dots QD. The inorganic matrix material Mx can fill the area (space) other than the multiple quantum dots QD in the light-emitting layer EL. The inorganic matrix material Mx can also partially or completely fill the multiple quantum dots QD. Multiple quantum dots QD can also be buried in the inorganic matrix material Mx at intervals. The inorganic matrix material Mx can show the part of the light-emitting layer except the multiple quantum dots QD.

[0038] The inorganic matrix material Mx may also completely or incompletely fill the area (space) outside the quantum dot group in the light-emitting layer. Here, three or more quantum dots QD are collectively referred to as a quantum dot group. In the present disclosure, as long as there is no special mention or contradiction, the structure of the inorganic matrix material MX, etc., in the cross-sectional observation of the light-emitting layer 5, it can be seen that the width of about 100nm is the desired structure, and the desired structure does not need to be observed in the entire light-emitting layer 5. The inorganic matrix material MX in the quantum dot layer can also be formed to have a 1000nm width along the surface direction orthogonal to the layer thickness direction. 2 A continuous film having an area of ​​1000 Å or more. A continuous film is a film that is not separated on one plane by materials other than the material constituting the continuous film. The continuous film may be an integrated film that is continuously connected by chemical bonding of the inorganic matrix material MX.

[0039] The periphery of the light-emitting layer may be formed of the inorganic matrix material MX so that the quantum dots QD are located away from the periphery. The periphery of the light-emitting layer does not have to be formed only of the inorganic matrix material Mx, and a part of the quantum dots QD may be exposed from the inorganic matrix material Mx.

[0040] The inorganic matrix material Mx may also be the same material as the shell contained in each of the multiple quantum dots QD. In the case where the shell of the quantum dot QD and the inorganic matrix material MX cannot be distinguished, the shell may also be regarded as a part of the inorganic matrix material MX. The inorganic matrix material MX may contain substances different from the inorganic compound (zinc sulfide, zinc selenide, etc.) as the main component as additives, impurities or residues. When analyzing the light-emitting layer containing the inorganic matrix material MX, the carbon atoms contained may be less than 5 atomic %.

[0041] Fig.17 Schematic diagram showing an example of the configuration of the display device of this embodiment. Fig.17 As shown, the display device 20 includes: a display unit DA including a plurality of sub-pixels SP, a first driver X1 and a second driver X2 for driving the plurality of sub-pixels SP, and a display control unit DC for controlling the first driver X1 and the second driver X2. The sub-pixel SP includes a light-emitting element 7 and a pixel circuit PC connected to the light-emitting element ED. The pixel circuit PC may also be connected to a scanning signal line GL, a data signal line DL, and a light-emitting control line EL. The scanning signal line GL and the light-emitting control line EL may also be connected to the first driver X1, and the data signal line DL may be connected to the second driver X2.

[0042] Fig.181 is a cross-sectional view showing an example of the schematic structure of the display device involved in the present embodiment. The display device 20 includes a substrate 13, a light-emitting element layer 14 and a sealing layer 15. The substrate 13 can also be a pixel circuit substrate including a supporting substrate 11 and a pixel circuit layer 12. The supporting substrate 11 can use a glass substrate, a resin substrate, etc. The supporting substrate 11 can also be flexible. The pixel circuit layer 12 includes, for example, a plurality of pixel circuits PC arranged in a matrix. The pixel circuit PC may include a pixel capacitor for writing a grayscale signal, a transistor for controlling the current value of the light-emitting element 7 according to the grayscale signal, a transistor connected to the scanning signal line GL and the data signal line DL, and a transistor connected to the light-emitting control line EL.

[0043] like Fig.18 As shown, the light-emitting element layer 14 includes, from the substrate 13 side, an anode EA, an edge covering film 2 covering the edge of the anode EA, a hole transport layer 4, a light-emitting layer 5, a functional layer 6F and a cathode EC. The functional layer 6F can be an electron transport layer. The light-emitting element layer 14 may include: a light-emitting element 7R (7) including a light-emitting layer 5R (5) emitting red light, a light-emitting element 7G (7) including a light-emitting layer 5G (5) emitting green light, and a light-emitting element 7B (7) including a light-emitting layer 5B (5) emitting blue light. The cathode EC can be located on the light extraction side. The sealing layer 15 includes inorganic insulating films such as silicon nitride films and silicon oxide films to prevent foreign matter (water, oxygen, etc.) from invading the light-emitting element layer 14.

[0044] The above-mentioned embodiments are for the purpose of illustration and description, and are not intended to be limiting. Based on these illustrations and descriptions, it should be apparent to those skilled in the art that various modifications can be made. Description of Reference Numerals

[0045] 4Hole transport layer 4F functional layer (hole transport layer) 5 Luminous Layer 6Electron transport layer 6F functional layer (electron transport layer) 7 Light-emitting element 8 cores 9 Shell EA Anode EC cathode QD Quantum Dots MX Inorganic Matrix Materials

Claims

1. A light emitting element, characterized in that: include: Anode and cathode; A light-emitting layer, located between the anode and the cathode, and comprising a plurality of quantum dots and an inorganic matrix material filling the spaces between the plurality of quantum dots; as well as The functional layer is disposed between the anode and the cathode so as to be adjacent to the light-emitting layer, and the constituent elements of the functional layer are the same as those of the inorganic matrix material but have a different composition ratio.

2. The light emitting element according to claim 1, characterized in that The plurality of quantum dots each have (i) a core and (ii) a shell, and the shell and the inorganic matrix material have the same constituent elements but different composition ratios or the same composition ratio.

3. The light emitting element according to claim 1 or 2, characterized in that: At least one of the plurality of quantum dots is in contact with the functional layer.

4. The light emitting element according to any one of claims 1 to 3, characterized in that: The functional layer and the inorganic matrix material contain metal elements and non-metal elements, respectively.

5. The light emitting element according to claim 4, characterized in that The metal element is zinc, and the non-metal element is sulfur or selenium.

6. The light emitting element according to claim 5, characterized in that The functional layer contains hydroxyl groups.

7. The light emitting element according to claim 2, characterized in that: The inorganic host material has a band gap larger than the plurality of quantum dots.

8. The light emitting element according to any one of claims 1 to 7, characterized in that: The functional layer is disposed between the light-emitting layer and the cathode.

9. The light emitting element according to claim 8, characterized in that The CBM of the functional layer is shallower than the CBM of the plurality of quantum dots.

10. The light emitting element according to claim 8 or 9, characterized in that: The CBM of the functional layer is deeper than the CBM of the inorganic matrix material.

11. The light emitting element according to any one of claims 8 to 10, characterized in that: The functional layer and the inorganic matrix material contain zinc and sulfur or selenium, respectively. The composition ratio of zinc in the functional layer is greater than the composition ratio of zinc in the inorganic matrix material.

12. The light emitting element according to claim 2, characterized in that: The material of the inorganic matrix material is the same as that of the shell.

13. The light emitting element according to any one of claims 8 to 12, characterized in that: The functional layer is a first electron transport layer, A second electron transport layer is disposed between the first electron transport layer and the cathode, The constituent elements of the second electron transport layer are the same as those of the first electron transport layer, but the composition ratio is different.

14. The light emitting element according to claim 13, characterized in that: The CBM of the second electron transport layer is deeper than the CBM of the first electron transport layer.

15. The light emitting element according to any one of claims 8 to 12, characterized in that: The functional layer is a first electron transport layer, A second electron transport layer is disposed between the first electron transport layer and the cathode, The electron mobility of the first electron transport layer is set to S1, and the thickness is set to Da, The electron mobility of the second electron transport layer is set to S2, and the thickness is set to Db, S1 / Yes 3 ≥S2 / Db 3 。 16. The light emitting element according to any one of claims 1 to 7, characterized in that: The functional layer is disposed between the light-emitting layer and the anode.

17. The light emitting element according to claim 16, characterized in that: The VBM of the functional layer is deeper than the VBM of the plurality of quantum dots.

18. The light emitting element according to claim 16 or 17, characterized in that: The VBM of the functional layer is shallower than the VBM of the inorganic matrix material.

19. The light emitting element according to any one of claims 16 to 18, characterized in that: The functional layer and the inorganic matrix material contain zinc and sulfur or selenium, The composition ratio of zinc in the functional layer is smaller than the composition ratio of zinc in the inorganic matrix material.

20. The light emitting element according to any one of claims 16 to 19, characterized in that: The functional layer is a first hole transport layer, A second hole transport layer is disposed between the first hole transport layer and the anode.

21. The light emitting element according to claim 20, characterized in that The hole mobility of the first hole transport layer is set to S3, and the thickness is set to Dc, The hole mobility of the second hole transport layer is set to S4, and the thickness is set to Dd, S3 / Dc 3 ≥S4 / Dd 3 。 22. A display device, characterized in that: The light-emitting device comprises the light-emitting element according to any one of claims 1 to 21.

23. The display device according to claim 22, characterized in that: The cathode is located on the light extraction side.

24. A method for manufacturing a light emitting element, characterized in that: include: A step of forming a lower electrode; A step of forming a light-emitting layer, wherein the light-emitting layer comprises a plurality of quantum dots and an inorganic matrix material filling spaces between the plurality of quantum dots; forming a functional layer on the light-emitting layer, the functional layer having the same constituent elements as the inorganic matrix material but a different composition ratio; and A step of forming an upper electrode.

25. The method for manufacturing a light emitting element according to claim 24, characterized in that: The functional layer is formed using a CBD (chemical bath deposition) method.

Images