WO2021142559A1 - 薄膜型白光led芯片 - Google Patents

薄膜型白光led芯片 Download PDF

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WO2021142559A1
WO2021142559A1 PCT/CN2020/071635 CN2020071635W WO2021142559A1 WO 2021142559 A1 WO2021142559 A1 WO 2021142559A1 CN 2020071635 W CN2020071635 W CN 2020071635W WO 2021142559 A1 WO2021142559 A1 WO 2021142559A1
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light
layer
transparent electrode
injection layer
led chip
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PCT/CN2020/071635
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English (en)
French (fr)
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陈梓铭
叶轩立
黎振超
曹镛
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华南理工大学
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Priority to PCT/CN2020/071635 priority Critical patent/WO2021142559A1/zh
Priority to US17/330,487 priority patent/US11984538B2/en
Publication of WO2021142559A1 publication Critical patent/WO2021142559A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/40—Materials therefor
    • H01L33/42—Transparent materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/38—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/483—Containers
    • H01L33/486—Containers adapted for surface mounting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/505—Wavelength conversion elements characterised by the shape, e.g. plate or foil
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots

Definitions

  • This application relates to the technical field of light emitting diodes (LEDs), in particular to a thin-film white light LED chip with high external quantum efficiency and low production cost.
  • LEDs light emitting diodes
  • White light lighting is closely related to human work and life.
  • White light lighting technology has been greatly developed so far.
  • white light emitting diodes have become one of the best alternatives to traditional lighting components (such as incandescent lamps and fluorescent lamps).
  • Energy-saving and environmentally friendly white LEDs are also the general trend as the main lighting components.
  • the thin-film white LED has a nanometer-level thickness of each layer, a small amount of material, and is compatible with processes such as squeegee coating and printing. The cost is lower, and large-area preparation and surface light source emission can be achieved. Therefore, it will gradually replace Traditional white light LED emitted by a point light source.
  • Scheme A is to use a blue LED chip (luminescence peak position 430nm-500nm) to excite red light (luminescence peak position 600nm-780nm) and Green light (luminescence peak position 500nm-560nm) two-color phosphor, or excites monochromatic yellow light (luminescence peak position 560nm-600nm) phosphor to emit light, and the whole is mixed into white light to emit light.
  • a blue LED chip luminance peak position 430nm-500nm
  • Green light luminescence peak position 500nm-560nm
  • monochromatic yellow light luminescence peak position 560nm-600nm
  • Scheme B is to use a purple LED chip (luminescence peak position 200nm-430nm) to excite the red, green and blue (or complementary colors) phosphors to emit light, and the whole is mixed into white light to emit light.
  • a purple LED chip luminescence peak position 200nm-430nm
  • red, green and blue (or complementary colors) phosphors to emit light, and the whole is mixed into white light to emit light.
  • the phosphor only down-converts the energy of the photons that can be emitted from the LED chip.
  • Scheme C is to construct a full electroluminescent LED chip with red, green and blue vertical stacks, and the three colors are blended into white light
  • Scheme D is to construct a full electroluminescent LED chip with red, green and blue horizontal stacking LED chip, three colors are blended into white light. Both of these schemes are realized by all electro-induced methods. Because the external quantum efficiency of red and green LEDs is higher than that of blue LEDs, they can achieve higher white LED efficiency than scheme A and scheme B; at the same time, in scheme D, since the red, green and blue LEDs can be driven independently, the ratio of the red, green and blue can be adjusted to achieve controllable white light color temperature.
  • the refractive index of the blue and violet LED chip 100 is much higher than that of the packaging medium 200 (usually epoxy resin) containing phosphor 210 on the outside. Therefore, photons are incident from the optically dense medium to the optically thin medium, resulting in a large amount of total reflection inside the chip 100 (as shown by the arrow in Figure 2), which limits the external extraction of photons.
  • the phosphor 210 is added to the package In the medium 200, it is far away from the LED chip and is in the far-field position (the actual distance between the phosphor 210 and the light-emitting layer of the LED chip 100 is at least several times the light-emitting wavelength), so only within the total reflection angle, it can be emitted to the outside of the chip to reach the package Only the photons of the medium 200 can be absorbed by the phosphor 210, and then the phosphor 210 emits fluorescence.
  • the purpose of the present application is to provide a thin-film white light LED chip that can significantly improve external quantum efficiency, reduce lighting energy consumption, and have low production costs.
  • the technical solution of the present application is to provide a thin-film white light LED chip, which includes a transparent substrate, a first transparent electrode, a light-emitting structure, a second transparent electrode, and a first phosphor layer arranged in sequence, wherein ,
  • the light-emitting structure includes a light-emitting layer and an electron injection layer and a hole injection layer provided on both sides thereof, and the total thickness of the electron injection layer and the second transparent electrode (inverted structure) or the hole injection
  • the total thickness of the layer and the second transparent electrode (upright structure) is less than one emission wavelength length of the light-emitting layer.
  • the light-emitting layer includes a violet light-emitting material with a light-emitting wavelength of 200nm-430nm or a blue light-emitting material with a light-emitting wavelength of 430nm-500nm.
  • the light-emitting structure includes the hole injection layer, the light-emitting layer, and the electron injection layer arranged in sequence, the electron injection layer is adjacent to the second transparent electrode, and the electron injection layer
  • the thickness of the hole injection layer is less than 200 nm, and the thickness of the hole injection layer is less than 1000 nm.
  • the light emitting structure includes the electron injection layer, the light emitting layer, and the hole injection layer arranged in sequence, the hole injection layer is adjacent to the second transparent electrode, and the hole
  • the thickness of the injection layer is less than 200 nm, and the thickness of the electron injection layer is less than 1000 nm.
  • the materials of the electron injection layer and the hole injection layer are at least one of organic polymers and small molecules, metal oxides, inorganic semiconductor materials, and organic-inorganic composites.
  • the optical material is at least one of organic light-emitting materials, quantum dots and nanocrystalline materials, inorganic light-emitting materials, and organic-inorganic hybrid light-emitting materials.
  • the thickness of the second transparent electrode is less than 100 nm
  • the thickness of the first transparent electrode is less than 1000 nm
  • the materials of the second transparent electrode and the first transparent electrode are both ultra-thin metal films and patterns.
  • the thin-film white light LED chip further includes a second phosphor layer, and the second phosphor layer is provided on a side of the transparent substrate away from the first transparent electrode, and the first The thickness of the phosphor layer and the second phosphor layer are both less than 1 mm.
  • the first phosphor layer and the second phosphor layer both include blue fluorescent materials with a luminescence wavelength range of 430nm-500nm, green fluorescent materials with a luminescence wavelength range of 500nm-560nm, and a luminescence wavelength range of 560nm-600nm. At least one of the yellow light fluorescent material and the red light fluorescent material with the luminescence wavelength range of 600nm-780nm.
  • the fluorescent materials of the first phosphor layer and the second phosphor layer are at least one of organic fluorescent materials, quantum dots and nanocrystalline materials, inorganic fluorescent materials, and organic-inorganic hybrid fluorescent materials .
  • the powder layer can be formed by vapor deposition, sputtering, spin coating, knife coating, vapor deposition, inkjet printing, drop coating, roll-to-roll printing, slit coating, screen printing, spraying or mechanical printing.
  • the thin-film white LED chip of the present application includes a transparent substrate, a first transparent electrode, a light-emitting structure, a second transparent electrode and a first phosphor layer arranged in sequence
  • the light-emitting structure includes The light-emitting layer and the electron injection layer and hole injection layer provided on both sides thereof, and the total thickness of the electron injection layer and the second transparent electrode (inverted structure) or the total thickness of the hole injection layer and the second transparent electrode (upright The structure) is less than one light-emitting wavelength length of the light-emitting layer.
  • the total thickness of the electron injection layer and the second transparent electrode (inverted structure) or the total thickness of the hole injection layer and the second transparent electrode (upright structure) is set to be less than one emission wavelength length of the light-emitting layer, so that The evanescent wave generated by total reflection can penetrate into the first phosphor layer and be absorbed by the first phosphor layer.
  • the actual utilization of photons inside the chip is improved, so that the LED
  • the overall external quantum efficiency of the chip is improved, thereby reducing lighting energy consumption, while ensuring white light emission, and low production costs.
  • FIG. 1 is a schematic diagram of the realization of a thin-film white light LED in the prior art.
  • Fig. 2 is a schematic diagram of the light-emitting principle of a thin-film white light LED chip in the prior art.
  • Fig. 3a is a schematic structural diagram of an embodiment of a thin-film white light LED chip with an inverted structure of the present application.
  • Fig. 3b is a schematic structural diagram of another embodiment of a thin-film white light LED chip with an inverted structure of the present application.
  • Fig. 4a is a schematic structural diagram of an embodiment of a thin-film white light LED chip with an upright structure of the present application.
  • 4b is a schematic structural diagram of another embodiment of a thin-film white light LED chip with an upright structure of the present application.
  • Figure 5a is a schematic diagram of the evanescent wave generated when a light wave is incident from an optically dense medium to an optically thin medium and undergoes total reflection.
  • Figure 5b is a schematic diagram of the evanescent wave penetration of a light wave incident from an optically dense medium to an optically thinner medium in a third layer of medium that can absorb photons.
  • Figure 6a is the voltage-current density curve of the quantum dot blue and two-color white LED chip.
  • Figure 6b is the current density-external quantum efficiency curve of the quantum dot blue and two-color white LED chip.
  • Figure 7a is a spectrogram of a quantum dot two-color white LED chip.
  • Figure 7b is a color coordinate diagram of a quantum dot two-color white LED chip.
  • Figure 8a is the voltage-current density curve of the perovskite blue and tri-color white LED chips.
  • Fig. 8b is the current density-external quantum efficiency curve of perovskite blue and tri-color white LED chips.
  • Figure 9a is a spectrum diagram of a perovskite three-color white LED chip.
  • Figure 9b is a color coordinate diagram of a perovskite three-color white LED chip.
  • the thin-film white LED chip 100 includes a transparent substrate 110, a first transparent electrode 120, a light-emitting structure 130, a second transparent electrode 140, and a first transparent substrate 110, a first transparent electrode 120, a light-emitting structure 130, and a first transparent Fluorescent powder layer 150.
  • the light-emitting structure 130 includes a light-emitting layer 131, a hole injection layer 132 and an electron injection layer 133 disposed on both sides thereof, and the total thickness of the electron injection layer 133 and the second transparent electrode 140 (inverted structure) or holes
  • the total thickness of the injection layer 132 and the second transparent electrode 140 is less than one light-emitting wavelength length of the light-emitting layer 131 (details will be described later).
  • the thin-film white light LED chip 100 of the present application may further include a second phosphor layer 160 disposed on the side of the transparent substrate 110 away from the first transparent electrode 120.
  • FIGS. 3a to 4b different embodiments of the thin-film white light LED chip 100 of the present application will be described separately.
  • the thin-film white LED chip 100 has an inverted structure, and specifically includes a transparent substrate 110, a first transparent electrode 120, The light emitting structure 130, the second transparent electrode 140, and the first phosphor layer 150.
  • the light emitting structure 130 includes a hole injection layer 132, a light emitting layer 131, and an electron injection layer 133 arranged in sequence, and the hole injection layer 132 is formed on the first phosphor layer. Between a transparent electrode 120 and the light-emitting layer 131, an electron injection layer 133 is formed between the light-emitting layer 131 and the second transparent electrode 140.
  • the thickness of the hole injection layer 132 is less than 1000 nm, and the thickness of the electron injection layer 133 is less than 200 nm.
  • the total thickness of the electron injection layer 133 and the second transparent electrode 140 is less than one emission wavelength length of the light-emitting layer 131.
  • the light-emitting layer 131 includes a violet light-emitting material with a light-emitting wavelength between 200 nm and 430 nm or a blue light-emitting material with a light-emitting wavelength between 430 nm and 500 nm. Therefore, the electron injection layer 133 and the second transparent
  • the total thickness of the electrode 140 is preferably less than 200 nm or less than 430 nm, which can be set flexibly according to different luminescent materials of the luminescent layer 131.
  • the light-emitting material of the light-emitting layer 131 is preferably at least one of organic light-emitting materials, quantum dots and nanocrystalline materials, inorganic light-emitting materials, and organic-inorganic hybrid light-emitting materials. limit.
  • the materials of the electron injection layer 133 and the hole injection layer 132 can be at least one of organic polymers and small molecules, metal oxides, inorganic semiconductor materials, and organic-inorganic composites, but are not limited to these materials. .
  • the thickness of the first transparent electrode 120 is less than 1000 nm, and the thickness of the second transparent electrode 140 is less than 100 nm.
  • the thickness of the electron injection layer 133 is less than 200 nm, and the thickness of the electron injection
  • the total thickness of the layer 133 and the second transparent electrode 140 is preferably less than 200 nm.
  • the materials of the first transparent electrode 120 and the second transparent electrode 140 can be ultra-thin metal films, patterned metal films, metal nanowires, metal nanorods, metal nanoparticles, organic polymers and small molecules, and metal oxides. , At least one of organic-inorganic composites, but not limited to these materials.
  • the transparent substrate 110 is a transparent non-conductive substrate, which may be a rigid inorganic substrate or a flexible and bendable organic polymer substrate.
  • the first phosphor layer 150 must be present in the device structure, and the thickness of the first phosphor layer 150 is less than 1 mm.
  • the first phosphor layer 150 includes a blue fluorescent material with a luminescent wavelength band of 430nm-500nm, a green fluorescent material with a luminescent wavelength band of 500nm-560nm, a yellow fluorescent material with a luminescent wavelength band of 560nm-600nm, and a red fluorescent material with a luminescent wavelength band of 600nm-780nm. At least one of light fluorescent materials.
  • the fluorescent material of the first phosphor layer 150 is preferably at least one of organic fluorescent materials, quantum dots and nanocrystalline materials, inorganic fluorescent materials, and organic-inorganic hybrid fluorescent materials, but is not limited to these. Material.
  • the thin-film white LED chip 100 with an inverted structure of the present application may further include a second phosphor layer 160, which is provided on the transparent substrate 110 The side away from the first transparent electrode 120, and the thickness of the second phosphor layer 160 is less than 1mm.
  • the second phosphor layer 160 does not necessarily exist in the device structure, and its main function is to supplement the first phosphor layer 150.
  • the fluorescent material of the second fluorescent powder layer 160 is the same as that of the first fluorescent powder layer 150, that is, the fluorescent material of the second fluorescent powder layer 160 also includes a blue fluorescent material with a luminescence wavelength range of 430nm-500nm, and a luminescence wavelength range of 500nm. -At least one of 560nm green fluorescent material, yellow fluorescent material with luminescence wavelength band between 560nm and 600nm, and red fluorescent material with luminescence wavelength band between 600nm and 780nm.
  • the fluorescent material of the second fluorescent powder layer 160 is preferably at least one of organic fluorescent materials, quantum dots and nanocrystalline materials, inorganic fluorescent materials, and organic-inorganic hybrid fluorescent materials.
  • the second fluorescent powder layer The fluorescent material of 160 is not limited to those listed here.
  • the thin-film white LED chip 100 with an inverted structure of this embodiment has all structural layers available through vapor deposition, sputtering, spin coating, squeegee coating, evaporation, inkjet printing, and dripping.
  • the transparent electrode 140, the first phosphor layer 150 and the second phosphor layer 160 can all be formed in one of the above-mentioned ways, so that the forming process of the thin-film white LED chip 100 is simple and the production cost is reduced.
  • FIGS. 4a-4b another embodiment of the thin-film white LED chip 100 of the present application is an upright structure.
  • the difference between the thin-film white LED chip 100 of the upright structure and the above-mentioned inverted structure is only: The arrangement of the light emitting structure 130 is different.
  • the light-emitting structure 130 includes an electron injection layer 133, a light-emitting layer 131, and a hole injection layer 132 sequentially arranged, wherein the electron injection layer 133 is formed between the first transparent electrode 120 and the light-emitting layer 131, and the hole is injected
  • the layer 132 is formed between the light-emitting layer 131 and the second transparent electrode 140, and the thickness of the electron injection layer 133 is less than 1000 nm, the thickness of the hole injection layer 132 is less than 200 nm, and the total of the hole injection layer 132 and the second transparent electrode 140 The thickness is less than one emission wavelength length of the light-emitting layer 131.
  • the total thickness of the hole injection layer 132 and the second transparent electrode 140 is flexibly set according to the different luminescent materials of the luminescent layer 131, for example, when the luminescent layer 131 includes a violet luminescent material with a luminescent wavelength between 200nm and 430nm Or in the case of a blue light emitting material with an emission wavelength between 430 nm and 500 nm, the total thickness of the hole injection layer 132 and the second transparent electrode 140 is preferably less than 200 nm or less than 430 nm. In a preferred embodiment, the total thickness of the hole injection layer 132 and the second transparent electrode 140 is less than 200 nm.
  • the thin-film white light LED chip 100 with the upright structure shown in FIG. 4a has only the first phosphor layer 150
  • the thin-film white light LED chip 100 with the upright structure shown in FIG. 4b also has the first phosphor layer 150.
  • the second phosphor layer 160 but in addition to the arrangement of the above-mentioned light-emitting structure 130, the structure, material and molding method of the other parts of the film-type white LED chip 100 of the upright structure of this embodiment are the same as those of the above-mentioned inverted structure of the film.
  • the white light LED chip 100 is the same, so it will not be repeated here.
  • the first layer of medium is an optically dense medium with a refractive index of n 1
  • the second layer of medium is an optically thinner medium with a refractive index of n 2 and n 1 >n 2 .
  • the evanescent wave E which penetrates into the second layer of medium, will appear.
  • the evanescent wave E is a plane wave in the direction parallel to the interface, resulting in the Goos-Hanchen displacement D, and its intensity varies in the direction F perpendicular to the interface.
  • the depth index decreases, and the penetration depth is about the order of one wavelength. But because the average Poynting vector of the evanescent wave in the vertical direction is 0, there is no actual energy flow that can propagate to the far field in this direction, and all photons are totally reflected into the first layer of medium.
  • the third layer of medium that can absorb photon energy is introduced before the evanescent wave intensity is completely attenuated, the refractive index of which is n 3 , it will partially absorb the energy of the evanescent wave and make it reflect to the first The energy of the layer medium is reduced, which destroys the occurrence of total reflection. Furthermore, if the third layer of the medium absorbs the evanescent wave energy, it can be down-converted into fluorescent light, then the photons outside the total reflection angle in the first layer of the medium can be down-converted to the photons of the third layer. The efficiency of the whole process depends on the fluorescence quantum efficiency of the third medium and the thickness of the second medium.
  • the photons originally confined by the total reflection inside the device can be slowly absorbed and consumed by the third layer of medium, and then converted into emission.
  • the actual photons to the external space greatly increase the external quantum efficiency of the LED chip as a whole.
  • the refractive index of the light-emitting layer 131 in the LED chip 100 is greater than the refractive index of the electron injection layer 133/hole injection layer 132.
  • the second medium is the composite layer of the electron injection layer 133 with the inverted structure and the second transparent electrode 140 (see Figures 3a-3b) or the upright structure
  • the composite layer of the hole injection layer 132 and the second transparent electrode 140 see Figures 4a-4b
  • the third layer of the medium is the first phosphor layer 150
  • the realization of white light emission solves the low-efficiency mode that the white light LED can only excite the far-field phosphor through the blue (or violet) LED chip at this stage.
  • FIG. 3a taking an inverted structure of the quantum dot two-color white light LED chip as an example, a specific implementation of the thin film white light LED chip 100 of the present application will be described.
  • the structure of the quantum dot two-color white LED chip 100 is shown in FIG. 3a, in which the transparent substrate 110 is glass, the first transparent electrode 120 is an indium tin oxide transparent electrode (ITO), and the hole injection layer 132 is Poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), the light-emitting layer 131 is cadmium selenide (CdSe) quantum dots, and the electron injection layer 133 is 1,3,5-tri( 1-Phenyl-1H-benzimidazol-2-yl)benzene (TPBi), the second transparent electrode 140 is lithium fluoride/aluminum (LiF/Al); in addition, the second transparent electrode 140 is also deposited with a A phosphor layer 150, the first phosphor layer 150 is red light quantum dot phosphor (CdTe). It should be noted that if the first phosphor layer 150 is not deposited, a quantum dot blue LED
  • the preparation steps of the quantum dot two-color white LED chip 100 of this specific embodiment are as follows: Before starting the preparation, first use isopropanol, deionized water, detergent, deionized water, and ITO conductive glass in sequence. Ultrasonic cleaning with isopropanol, and then placed in an oven to dry until dry; in addition, before use, the ITO conductive glass sheet needs to be cleaned in a plasma surface cleaner for 4 minutes.
  • PEDOT:PSS poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid
  • CLEVIOS P VP CH 8000 poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid
  • KW-4A homogenizer
  • the thickness is about 30nm and annealed at 120°C for 20min to obtain the hole injection layer 132; then, cadmium selenide (CdSe) is spin-coated on the hole injection layer 132 to obtain the light-emitting layer 131, the light-emitting layer
  • the thickness of 131 is about 20 nm; then, the electron injection layer 133 and the second transparent electrode 140 are formed.
  • the TPBi electron injection layer material, the electron injection interface LiF, and the ultra-thin Al electrode are sequentially deposited on the CdSe light-emitting layer by evaporation. On 131, the thickness is 35nm, 1nm and 10nm respectively; finally, the first phosphor layer 150 (CdTe) is deposited on the ultra-thin Al electrode by spin coating, the thickness is about 100nm.
  • the above steps are completed to obtain the quantum dot two-color white LED chip 100. If the first phosphor layer 150 is not deposited, the obtained quantum dot blue LED chip with an inverted structure is obtained.
  • Figure 6a shows the voltage-current density curve of the quantum dot blue and quantum dot dual-color white LED chip. From this figure, it can be seen that the deposition of the first phosphor layer 150 does not affect the electrical characteristics of the blue quantum dot LED chip. . In addition, it can be seen from the current density-external quantum efficiency curve of the quantum dot blue light and the quantum dot two-color white light LED chip shown in FIG.
  • the refractive index (about 2.3) of the quantum dot light-emitting layer 131 is much larger than that of the TPBi electron injection layer 133.
  • the refractive index (about 1.7) so total reflection will greatly limit the emission of photons, resulting in a low external quantum efficiency of the quantum dot blue LED chip (about 4%); however, when the first phosphor layer 150 is introduced Later, because the evanescent wave generated during total reflection was used, the actual utilization of photons inside the chip was increased by absorbing the evanescent wave and then emitting fluorescence, so that the external quantum efficiency of the chip was increased to 5.7%. An increase of about 43%.
  • the light emission of the quantum dot two-color white LED chip 100 of this specific embodiment is composed of sky blue light (emitted by the chip) and red light (emitted by phosphor powder), it can be seen from Figure 7a It can be seen from the spectrum diagram shown that two-color white light is formed by the principle of complementary colors, and from the color coordinates shown in Figure 7b, it can be seen that the color coordinates of the quantum dot two-color white light LED chip 100 are at the (0.33, 0.33) position, indicating Its light color is pure white light.
  • the structure of the perovskite three-color white LED chip 100 is shown in FIG. 3b, wherein the transparent substrate 110 is glass, the first transparent electrode 120 is an indium tin oxide transparent electrode (ITO), and a hole injection layer 132 is poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), and its light-emitting layer 131 is an organic-inorganic hybrid perovskite PEA 2 Cs n-1 Pb n (Cl x Br 3 -x ) 3n+1 , the electron injection layer 133 is 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), and the second transparent electrode 140 is lithium fluoride /Aluminum (LiF/Al);
  • a first phosphor layer 150 is deposited on the second transparent electrode 140, and the first phosphor layer 150 is a red light perovskite
  • first phosphor layer 150 and the second phosphor layer 160 are not deposited, a perovskite blue LED chip with an inverted structure is formed.
  • the preparation steps of the organic-inorganic hybrid perovskite three-color white light LED chip 100 of this specific embodiment are as follows: before use, ITO conductive glass, isopropanol, deionized water, and detergent are used in sequence. , Deionized water, isopropanol ultrasonic cleaning, and then placed in an oven to dry until it is dry, before the start of manufacturing, the ITO glass sheet needs to be cleaned again in a plasma surface cleaner for 4 minutes.
  • PEDOT:PSS poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid
  • CLEVIOS P VP CH 8000 poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid
  • KW-4A homogenizer
  • the thickness is about 30nm, and it is annealed at 120°C for 20min to obtain the hole injection layer 132; then, the PEA 2 Cs n-1 Pb n (Cl x Br 3-x ) 3n+1 material is spin-coated on
  • the hole injection layer 132 has a thickness of about 50 nm and is annealed at 70° C.
  • the electron injection layer 133 and the second transparent electrode 140 are formed, specifically, the TPBi electron injection layer material, electron
  • the injected interface LiF and the ultra-thin Al electrode were deposited on the perovskite luminescent layer 131 by evaporation in order, with thicknesses of 35nm, 1nm and 10nm respectively; then, the first phosphor layer 150 (CsPbBr 0.5 I 2.5 ) was spun
  • the coating method is deposited on the ultra-thin Al electrode with a thickness of about 100 nm; the second phosphor layer 160 (CsPbBr 2.5 I 0.5 ) is deposited on the glass substrate in a spin coating method with a thickness of about 50 nm to complete the preparation step.
  • the perovskite blue LED chip with an inverted structure is obtained.
  • Figure 8a shows the voltage-current density curve of the perovskite blue and perovskite three-color white LED chips. It can be seen from Figure 8a that the deposition of the first phosphor layer 150 and the second phosphor layer 160 hardly affects calcium Electrical characteristics of titanium ore blue LED chips.
  • the refractive index (about 2.5) of the perovskite light-emitting layer 131 is much larger than that of TPBi.
  • the refractive index (about 1.7) and total reflection of the electron injection layer 133 also greatly limit the emission of photons, resulting in the low external quantum efficiency of the perovskite blue perovskite LED chip (about 3.5%); however, when After the introduction of the first phosphor layer 150, the evanescent wave generated during total reflection is utilized. By absorbing the evanescent wave and emitting fluorescence, the actual utilization of photons inside the chip is improved, and the external quantum of the chip is improved. The efficiency is increased to 4.8%, which is an increase of about 37%.
  • the increase in efficiency is not as good as that in the aforementioned quantum dot two-color white LED chip 100.
  • the reason is that the introduction of the second phosphor layer 160 in the far field cannot make a positive contribution to the efficiency of the device.
  • the fluorescence quantum efficiency is less than 100%, which leads to a negative contribution to the external quantum efficiency of the chip.
  • the external quantum efficiency of the perovskite three-color white LED chip of this specific embodiment is still much higher than that of the perovskite in the prior art.
  • Mineral white light LED chip is still much higher than that of the perovskite in the prior art.
  • perovskite blue and perovskite three-color white LED chips of this specific embodiment emit blue light (emitted by the chip) and red light (emitted by the first phosphor layer 150) ) And green light (emitted by the second phosphor layer 160), as shown in Figure 9a, three-color white light is formed by the principle of three primary colors, and the color coordinates of the perovskite three-color white LED chip are at (0.29, 0.37) The position, as shown in Figure 9b, indicates that its light color is pure white light.
  • the thin film white light LED chip 100 of the present application includes a transparent substrate 110, a first transparent electrode 120, a light emitting structure 130, a second transparent electrode 140, and a first phosphor layer 150, which are arranged in sequence
  • the light emitting The structure 130 includes a light-emitting layer 131, an electron injection layer 133 and a hole injection layer 132 disposed on both sides thereof, and the total thickness of the electron injection layer 133 and the second transparent electrode 140 (inverted structure) or the hole injection layer 132 and the second transparent electrode 140
  • the total thickness of the two transparent electrodes 140 is less than the length of one emission wavelength of the light-emitting layer 131.
  • the photons emitted by the light-emitting layer 131 will not be completely reflected in this direction, but have the opportunity to penetrate into the first phosphor.
  • Layer 150 secondly, the total thickness of the electron injection layer 133 and the second transparent electrode 140 (inverted structure) or the total thickness of the hole injection layer 132 and the second transparent electrode 140 (upright structure) is less than a light emitting layer 131
  • the wavelength length is set so that the evanescent wave generated by total reflection can penetrate into the first phosphor layer 150 and be absorbed by the first phosphor layer 150.
  • the internal chip is improved.
  • the actual utilization of photons improves the overall external quantum efficiency of the LED chip, thereby reducing lighting energy consumption, while ensuring white light emission and low production costs.

Abstract

一种薄膜型白光LED芯片，其包括依次设置的透明衬底、第一透明电极、发光结构、第二透明电极及第一荧光粉层，其中，发光结构包括发光层及设于其两侧的电子注入层及空穴注入层，且电子注入层与第二透明电极的总厚度(倒置结构)或空穴注入层与第二透明电极的总厚度(正置结构)小于发光层的一个发光波长长度。通过第二透明电极的设置使发光层所发出的光子有机会渗透到第一荧光粉层，而电子注入层与第二透明电极的总厚度(倒置结构)或空穴注入层与第二透明电极的总厚度(正置结构)小于发光层的一个发光波长长度，则使得因全反射所产生的隐失波能够渗透至第一荧光粉层而被第一荧光粉层所吸收而发光，从而使得LED芯片的整体外量子效率提高。

Description

薄膜型白光LED芯片 技术领域
本申请涉及发光二极管(LED)技术领域，尤其涉及一种外量子效率高、生产成本低的薄膜型白光LED芯片。
背景技术
白光照明和人类的工作生活息息相关，白光照明技术至今已经获得了大幅发展，其中白光发光二极管(LED)已经成为替代传统照明发光元件(如白炽灯、荧光灯)的最佳选择之一，使用绿色、节能、环保的白光LED作为主要照明元件也是大势所趋。而薄膜型白光LED由于每层厚度都在纳米量级，材料用量少，还可以与刮涂、印刷等工艺兼容，成本更低，并且可以实现大面积制备以及面光源发射，因此将逐渐替代点光源发射的传统白光LED。
下面参看图1所示，现阶段实现薄膜型白光LED照明主要有以下几种方案：方案A是利用蓝光LED芯片(发光峰位430nm-500nm)，激发红光(发光峰位600nm-780nm)和绿光(发光峰位500nm-560nm)双色荧光粉，或者激发单色黄光(发光峰位560nm-600nm)荧光粉发光，整体混合成白光出光。方案B是利用紫光LED芯片(发光峰位200nm-430nm)，激发红绿蓝三色(或互补色)荧光粉发光，整体混合成白光出光。以上两种“电致+光致”白光LED实现方式的优势是电路驱动以及LED的制备工艺相对简单，整体的成本相对低廉，同时各色荧光粉往往添加在蓝光(或紫光)LED芯片的封装层中，远离蓝光(或紫光)LED芯片的发光层，因此是一种远场激发，荧光粉只对能够射出LED芯片的光子进行能量的下转换。
继续参看图1所示，方案C是构筑红绿蓝三色纵向叠层的全电致发光LED芯片，三色共混成白光；方案D则是构筑红绿蓝三色横向堆叠的全电致发光LED 芯片，三色共混成白光。这两种方案都通过全电致方式实现，由于红光以及绿光LED的外量子效率比蓝光LED的要高，因此都能获得比方案A和方案B更高的白光LED效率；同时，在方案D中，由于红绿蓝三色LED可以独立驱动，从而可以调控红绿蓝三色的比例以实现白光色温的可控。
下面参看图2所示，在现有的方案A以及方案B中，由于蓝光以及紫光LED芯片100的折射率远高于外部含有荧光粉210的封装介质200(通常为环氧树脂)的折射率，因此光子由光密介质入射到光疏介质，导致全反射在芯片100的内部大量产生(如图2中箭头方式所示)，限制了光子的外部提取，然而，荧光粉210被添加至封装介质200中，远离LED芯片，处于远场位置(荧光粉210与LED芯片100的发光层的实际距离至少大于数倍的发光波长)，因此只有在全反射角内，能够出射到芯片外部到达封装介质200的光子才能被荧光粉210吸收，然后再进行荧光粉210的荧光发射。但是蓝光以及紫光LED的外量子效率较低，以及荧光粉不足100％的荧光量子效率，严重影响了白光LED的整体效率，使得“电致+光致”这种形式的白光LED效率更为低下。另外，仅针对方案B而言，其光谱中强的紫外成分对人体有一定的危害，尤其在长时间照射的情况下，因此，考虑到紫外线对人体的影响，在“电致+光致”的白光实现方式中，用蓝光LED芯片激发红绿光(或黄光)荧光粉(方案A)仍是现在商业化白光LED的第一选择，尽管其效率低下。
再次参看图1，对于方案C，虽然该方式能够获得高效的白光LED芯片，但是器件制备工艺繁复，整个芯片涉及到十几层以上的薄膜沉积工艺，成本非常高。而对于方案D，由于红绿蓝三色LED都需要独立的驱动电路，使每个白光LED驱动电路的数量提高到三套，并且驱动电路设计复杂，同样需要非常高的成本，同时牺牲了横向尺寸，通常不作为照明元件使用。由于制备成本的问题，方案C和方案D中的两种白光照明方案的市场占有率非常低。
因此，有必要提供一种能够显著提高“电致+光致”型主流白光LED的发光效率、降低白光LED的照明能耗并且生产成本低的薄膜型白光LED芯片，以解决上述现有技术中所存在的问题。
申请内容
本申请的目的在于提供一种能够显著提高外量子效率、降低照明能耗并且生产成本低的薄膜型白光LED芯片。
为实现上述目的，本申请的技术方案为：提供一种薄膜型白光LED芯片，其包括依次设置的透明衬底、第一透明电极、发光结构、第二透明电极及第一荧光粉层，其中，所述发光结构包括发光层及设于其两侧的电子注入层及空穴注入层，且所述电子注入层与所述第二透明电极的总厚度(倒置结构)或所述空穴注入层与所述第二透明电极的总厚度(正置结构)小于所述发光层的一个发光波长长度。
较佳地，所述发光层包括发光波长在200nm-430nm的紫光发光材料或发光波长在430nm-500nm的蓝光发光材料。
较佳地，所述发光结构包括依次设置的所述空穴注入层、所述发光层及所述电子注入层，所述电子注入层与所述第二透明电极邻接，且所述电子注入层的厚度小于200nm，所述空穴注入层的厚度小于1000nm。
较佳地，所述发光结构包括依次设置的所述电子注入层、所述发光层及所述空穴注入层，所述空穴注入层与所述第二透明电极邻接，且所述空穴注入层的厚度小于200nm，所述电子注入层的厚度小于1000nm。
较佳地，所述电子注入层、所述空穴注入层的材料均为有机聚合物和小分子、金属氧化物、无机半导体材料、有机无机复合物中的至少一种，所述发光层的光材料为有机发光材料、量子点和纳米晶材料、无机发光材料、有机无机杂化发光材料中的至少一种。
较佳地，所述第二透明电极的厚度小于100nm，所述第一透明电极的厚度小于1000nm，且所述第二透明电极、所述第一透明电极的材料均为超薄金属膜、图案化金属膜、金属纳米线、金属纳米棒、金属纳米颗粒、有机聚合物及小分子、金属氧化物、有机无机复合物中的至少一种。
较佳地，所述薄膜型白光LED芯片还包括第二荧光粉层，所述第二荧光粉层设于所述透明衬底的远离所述第一透明电极的一侧，且所述第一荧光粉层、所述第二荧光粉层的厚度均小于1mm。
较佳地，所述第一荧光粉层、所述第二荧光粉层均包括发光波段在430nm-500nm的蓝光荧光材料、发光波段在500nm-560nm的绿光荧光材料、发光波段在560nm-600nm的黄光荧光材料、发光波段在600nm-780nm的红光荧光材料中的至少一种。
较佳地，所述第一荧光粉层、所述第二荧光粉层的荧光材料均为有机荧光材料、量子点和纳米晶材料、无机荧光材料、有机无机杂化荧光材料中的至少一种。
较佳地，所述第一透明电极、所述发光层、所述电子注入层、所述及空穴注入层、所述第二透明电极、所述第一荧光粉层及所述第二荧光粉层均可通过气相沉积、溅射、旋涂、刮涂、蒸镀、喷墨打印、滴涂、卷对卷印刷、狭缝涂布、丝网印刷、喷涂或机械印压的方式成型。
与现有技术相比，由于本申请的薄膜型白光LED芯片，其包括依次设置的透明衬底、第一透明电极、发光结构、第二透明电极及第一荧光粉层，其中，发光结构包括发光层及设于其两侧的电子注入层及空穴注入层，且电子注入层与第二透明电极的总厚度(倒置结构)或空穴注入层与第二透明电极的总厚度(正置结构)小于所述发光层的一个发光波长长度。首先，由于将现有技术中的反射金属电极替换为第二透明电极，因此能够让发光层所发出的光子在该方向上不会进行完全反射，而是有机会渗透到第一荧光粉层；其次，通过电子注入层与第二透明电极的总厚度(倒置结构)或空穴注入层与第二透明电极的总厚度(正置结构)小于所述发光层的一个发光波长长度的设置，使得因全反射所产生的隐失波能够渗透至第一荧光粉层而被第一荧光粉层所吸收，通过吸收隐失波再发出荧光的方式，提高了芯片内部光子的实际利用率，使得LED芯片的整体外量子效率提高，进而降低照明能耗，同时能够保证白光发射，并且生产成本低。
附图说明
图1是现有技术中薄膜型白光LED的实现原理图。
图2是现有技术中薄膜型白光LED芯片的出光原理示意图。
图3a是本申请倒置结构的薄膜型白光LED芯片一实施例的结构示意图。
图3b是本申请倒置结构的薄膜型白光LED芯片另一实施例的结构示意图。
图4a是本申请正置结构的薄膜型白光LED芯片一实施例的结构示意图。
图4b是本申请正置结构的薄膜型白光LED芯片另一实施例的结构示意图。
图5a是光波由光密介质入射到光疏介质发生全反射时所产生的隐失波示意图。
图5b是在具有可吸收光子的第三层介质时光波由光密介质入射到光疏介质的隐失波渗透示意图。
图6a是量子点蓝光及双色白光LED芯片的电压-电流密度曲线。
图6b是量子点蓝光及双色白光LED芯片的电流密度-外量子效率曲线。
图7a是量子点双色白光LED芯片的光谱图。
图7b是量子点双色白光LED芯片的色坐标图。
图8a是钙钛矿蓝光及三色白光LED芯片的电压-电流密度曲线。
图8b是钙钛矿蓝光及三色白光LED芯片的电流密度-外量子效率曲线。
图9a是钙钛矿三色白光LED芯片的光谱图。
图9b是钙钛矿三色白光LED芯片的色坐标图。
具体实施方式
现在参考附图描述本申请的实施例，附图中类似的元件标号代表类似的元件。
下面先结合图3a-图4b所示，本申请提供的薄膜型白光LED芯片100，其包括依次设置的透明衬底110、第一透明电极120、发光结构130、第二透明电极140及第一荧光粉层150。其中，所述发光结构130包括发光层131及设于其两侧的空穴注入层132及电子注入层133，且电子注入层133与第二透明电极140的总厚度(倒置结构)或空穴注入层132与第二透明电极140的总厚度(正置结构)小于所述发光层131的一个发光波长长度(详见后述)。
更进一步地，本申请的薄膜型白光LED芯片100还可以包括第二荧光粉层 160，所述第二荧光粉层160设于透明衬底110的远离第一透明电极120的一侧。
下面分别参看图3a-图4b所示，对本申请的薄膜型白光LED芯片100的不同实施例分别进行说明。
首先参看图3a所示，在本申请之薄膜型白光LED芯片100的一实施例中，该薄膜型白光LED芯片100为倒置结构，具体包括依次设置的透明衬底110、第一透明电极120、发光结构130、第二透明电极140及第一荧光粉层150，其中，发光结构130包括依次设置的空穴注入层132、发光层131及电子注入层133，且空穴注入层132成型于第一透明电极120与发光层131之间，电子注入层133成型于发光层131与第二透明电极140之间，同时，空穴注入层132的厚度小于1000nm，电子注入层133的厚度小于200nm，并且，所述电子注入层133与第二透明电极140的总厚度小于发光层131的一个发光波长长度。
在本实施例中，所述发光层131包括发光波长在200nm-430nm之间的紫光发光材料或发光波长在430nm-500nm之间的蓝光发光材料，因此，所述电子注入层133与第二透明电极140的总厚度优选小于200nm或小于430nm，具体根据发光层131的不同发光材料灵活设置。
继续参看图3a所示，所述发光层131的发光材料优选为有机发光材料、量子点和纳米晶材料、无机发光材料、有机无机杂化发光材料中的至少一种，但并不以此为限。另外，所述电子注入层133、空穴注入层132的材料均可以是有机聚合物和小分子、金属氧化物、无机半导体材料、有机无机复合物中的至少一种，但也不限于这些材料。
再次参看图3a所示，本实施例中，所述第一透明电极120的厚度小于1000nm，第二透明电极140的厚度小于100nm，如上所述，电子注入层133的厚度小于200nm，而电子注入层133和第二透明电极140的总厚度则优选小于200nm。另外，第一透明电极120与第二透明电极140的材料均可以采用超薄金属膜、图案化金属膜、金属纳米线、金属纳米棒、金属纳米颗粒、有机聚合物及小分子、金属氧化物、有机无机复合物中的至少一种，但并不限于这些材料。再者，所述透明衬底110为透明不导电衬底，其可以为刚性的无机物衬底，也可以为柔性可弯曲的有机聚合物衬底。
请再参看图3a所示，所述第一荧光粉层150必须存在于器件结构中，且该第一荧光粉层150的厚度小于1mm。第一荧光粉层150包括发光波段在430nm-500nm的蓝光荧光材料、发光波段在500nm-560nm的绿光荧光材料、发光波段在560nm-600nm的黄光荧光材料、发光波段在600nm-780nm的红光荧光材料中的至少一种。在本实施例中，该第一荧光粉层150的荧光材料优选为有机荧光材料、量子点和纳米晶材料、无机荧光材料、有机无机杂化荧光材料中的至少一种，但并不限于这些材料。
下面参看图3b所示，在本申请倒置结构的薄膜型白光LED芯片100的另一实施例中，其还可以进一步包括第二荧光粉层160，第二荧光粉层160设于透明衬底110的远离第一透明电极120的一侧，且第二荧光粉层160的厚度小于1mm，该第二荧光粉层160非必须存在于器件结构中，其主要作用为补充第一荧光粉层150所不能覆盖的发光波段。
另外，该第二荧光粉层160的荧光材料与第一荧光粉层150的相同，即，第二荧光粉层160的荧光材料也包括发光波段在430nm-500nm的蓝光荧光材料、发光波段在500nm-560nm的绿光荧光材料、发光波段在560nm-600nm的黄光荧光材料、发光波段在600nm-780nm的红光荧光材料中的至少一种。本实施例中，第二荧光粉层160的荧光材料优选为有机荧光材料、量子点和纳米晶材料、无机荧光材料、有机无机杂化荧光材料中的至少一种，当然，第二荧光粉层160的荧光材料也不以此处列举的为限。
再次结合图3a-3b所示，本实施例之倒置结构的薄膜型白光LED芯片100，其所有结构层均可以通过气相沉积、溅射、旋涂、刮涂、蒸镀、喷墨打印、滴涂、卷对卷印刷、狭缝涂布、丝网印刷、喷涂或机械印压的方式成型，即，第一透明电极120、空穴注入层132、发光层131、电子注入层133、第二透明电极140、第一荧光粉层150及第二荧光粉层160均可以通过上述方式之一成型，使薄膜型白光LED芯片100的成型工艺简单，生产成本降低。
下面参看图4a-4b所示，本申请薄膜型白光LED芯片100的另一种实施方式为正置结构，该正置结构的薄膜型白光LED芯片100与上述倒置结构的不同之处仅在于：发光结构130的设置方式不同。
具体地，所述发光结构130包括依次设置的电子注入层133、发光层131及空穴注入层132，其中，电子注入层133成型于第一透明电极120与发光层131之间，空穴注入层132成型于发光层131与第二透明电极140之间，且电子注入层133的厚度小于1000nm，空穴注入层132的厚度小于200nm，同时空穴注入层132与第二透明电极140的总厚度小于所述发光层131的一个发光波长长度。
与上述实施方式相同，空穴注入层132与第二透明电极140的总厚度根据发光层131的不同发光材料灵活设置，例如，当发光层131包括发光波长在200nm-430nm之间的紫光发光材料或发光波长在430nm-500nm之间的蓝光发光材料时，空穴注入层132与第二透明电极140的总厚度优选小于200nm或小于430nm。在一种较佳实施方式中，空穴注入层132与第二透明电极140的总厚度小于200nm。
另外，图4a所示之正置结构的薄膜型白光LED芯片100仅设有第一荧光粉层150，图4b所示之正置结构的薄膜型白光LED芯片100同时具有第一荧光粉层150及第二荧光粉层160，但是除上述发光结构130的设置之外，本实施方式之正置结构的薄膜型白光LED芯片100的其他部分的结构、材料及成型方式均与上述倒置结构的薄膜型白光LED芯片100相同，因此不再赘述。
下面参看图5a所示，对光波由光密介质入射到光疏介质发生全反射时所产生的隐失波进行说明。如图5a所示，第一层介质为光密介质，其折射率为n 1，第二层介质为光疏介质，其折射率为n 2，且n 1>n 2，当光波E由光密介质入射到光疏介质且入射角大于全反射角时，将发生全反射，全反射光E`反射到第一层介质中，在全反射发生的情况下，根据光的波动性，界面上将出现渗透到第二层介质的隐失波E``，隐失波E``在平行于界面方向是平面波，导致了Goos-Hanchen位移D，而其强度在垂直于界面的方向F上随深度指数递减，其渗透深度约为一个波长的数量级。但由于隐失波在竖直方向的平均波印廷矢量为0，所以在该方向上并没有可以往远场传播的实际能流，所有光子全反射到第一层介质中。
如图5b所示，如果在隐失波强度完全衰减之前，引入可吸收光子能量的第 三层介质，其折射率为n 3，将可以部分吸收掉隐失波的能量，使得反射到第一层介质的能量减少，破坏了全反射的发生。再者，如果第三层介质在吸收隐失波能量之后，能够下转换成荧光发光，则能让第一层介质中处于全反射角外的光子下转换为第三层介质的光子出射，而整个过程的效率取决于第三层介质的荧光量子效率以及第二层介质的厚度。因此，通过这样一个器件近场光学的整体偶联，以隐失波为媒介，就可以让原本被全反射束缚于器件内部的光子慢慢地被第三层介质吸收消耗，然后转化为可以出射到外部空间的实际光子，从而太太地提高了LED芯片整体的外量子效率。
结合图3a-4b及图5b所示，在绝大部分情况下，LED芯片100中的发光层131的折射率大于电子注入层133/空穴注入层132的折射率。根据图5b所示的原理，当第一层介质为发光层131，第二层介质为倒置结构的电子注入层133与第二透明电极140的复合层(见图3a-3b)或正置结构的空穴注入层132与第二透明电极140的复合层(见图4a-4b)，第三层介质为第一荧光粉层150时，则可以在提高LED芯片100的整体外量子效率的同时实现白光发射，解决了现阶段白光LED只能通过蓝光(或紫光)LED芯片激发远场荧光粉的低效模式。
下面再次参看图3a所示，以倒置结构的量子点双色白光LED芯片为例，对本申请之薄膜型白光LED芯片100的一具体实现方式进行说明。
具体地，所述量子点双色白光LED芯片100的结构如图3a所示，其中，透明衬底110为玻璃，第一透明电极120为氧化铟锡透明电极(ITO)，空穴注入层132为聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸(PEDOT:PSS)，其发光层131为硒化镉(CdSe)量子点，电子注入层133为1,3,5-三(1-苯基-1H-苯并咪唑-2-基)苯(TPBi)，第二透明电极140为氟化锂/铝(LiF/Al)；另外，第二透明电极140的上方还沉积有第一荧光粉层150，该第一荧光粉层150为红光量子点荧光粉(CdTe)。其中需要说明的是，如果不沉积第一荧光粉层150，则构成倒置结构的量子点蓝光LED芯片。
再次参看图3a所示，本具体实施例之量子点双色白光LED芯片100的制备步骤如下：开始制备之前，先将ITO导电玻璃依次用异丙醇、去离子水、洗涤剂、去离子水、异丙醇超声清洗，然后置于烘箱中烘至干燥；另外在使用前， 还需将ITO导电玻璃片在等离子表面清洗仪中清洗4分钟。
开始制备时，首先，将聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸(PEDOT:PSS)(CLEVIOS P VP CH 8000)用匀胶机(KW-4A)高速旋涂于ITO导电玻璃上，厚度约为30nm，并以120℃退火20min，以得到空穴注入层132；然后，将硒化镉(CdSe)旋涂于空穴注入层132上以得到发光层131，发光层131的厚度约为20nm；接着，成型电子注入层133及第二透明电极140，具体地，TPBi电子注入层材料、电子注入界面LiF以及超薄Al电极依次以蒸镀的方式沉积在CdSe发光层131上，厚度分别为35nm、1nm以及10nm；最后，将第一荧光粉层150(CdTe)以旋涂方式沉积于超薄Al电极上，厚度约为100nm。完成上述步骤从而得到量子点双色白光LED芯片100，如果不沉积第一荧光粉层150，则得到的是倒置结构的量子点蓝光LED芯片。
下面结合图3a、图6a-6b所示，对倒置结构的量子点蓝光LED芯片与本申请的量子点双色白光LED芯片100的电学特性及外量子效率进行比较。图6a所示其为量子点蓝光及量子点双色白光LED芯片的电压-电流密度曲线，从该图中可看出第一荧光粉层150的沉积并不会影响蓝光量子点LED芯片的电学特性。另外，从图6b所示的量子点蓝光以及量子点双色白光LED芯片的电流密度-外量子效率曲线可看出，由于量子点发光层131的折射率(约2.3)远大于TPBi电子注入层133的折射率(约1.7)，因此全反射将极大地限制了光子的出射，导致了量子点蓝光LED芯片的外量子效率较低(约为4％)；然而，当引入第一荧光粉层150后，由于对全反射时所产生的隐失波进行了利用，通过吸收隐失波再发出荧光的方式，提高了芯片内部光子的实际利用率，使得芯片的外量子效率提高到5.7％，获得了约43％的提高。
下面结合图3a、图7a-7b所示，由于本具体实施例之量子点双色白光LED芯片100的发光由天蓝光(芯片发出)以及红光(荧光粉发出)组成，因此，从图7a所示的光谱图可看出，通过互补色原理构成了双色白光，而从图7b所示的色坐标可看出，该量子点双色白光LED芯片100的色坐标处于(0.33,0.33)位置，表明其光色为纯正的白光。
下面再次参看图3b所示，以倒置结构的有机无机杂化钙钛矿三色白光LED 芯片100为例，对本申请之薄膜型白光LED芯片100的另一具体实现方式进行说明。
具体地，所述钙钛矿三色白光LED芯片100的结构如图3b所示，其中，透明衬底110为玻璃，第一透明电极120为氧化铟锡透明电极(ITO)，空穴注入层132为聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸(PEDOT:PSS)，其发光层131为有机无机杂化钙钛矿PEA 2Cs n-1Pb n(Cl xBr 3-x) 3n+1，其电子注入层133为1,3,5-三(1-苯基-1H-苯并咪唑-2-基)苯(TPBi)，第二透明电极140为氟化锂/铝(LiF/Al)；另外，第二透明电极140的上方还沉积有第一荧光粉层150，该第一荧光粉层150为红光钙钛矿荧光粉(CsPbBr 0.5I 2.5)，还在透明衬底110的底侧沉积有第二荧光粉层160，该第二荧光粉层160为绿光钙钛矿荧光粉(CsPbBr 2.5I 0.5)。
其中需要说明的是，如果不沉积第一荧光粉层150、第二荧光粉层160，则构成倒置结构的钙钛矿蓝光LED芯片。
再次参看图3b所示，本具体实施例之有机无机杂化钙钛矿三色白光LED芯片100的制备步骤如下：使用前，将ITO导电玻璃、依次用异丙醇、去离子水、洗涤剂、去离子水、异丙醇超声清洗，然后置于烘箱中烘至干燥，开始制造之前，还需将ITO玻璃片在等离子表面清洗仪中再次清洗4分钟。
开始制备时，首先，将聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸(PEDOT:PSS)(CLEVIOS P VP CH 8000)用匀胶机(KW-4A)高速旋涂于ITO导电玻璃上，厚度约为30nm，并以120℃退火20min，以得到空穴注入层132；然后，将PEA 2Cs n-1Pb n(Cl xBr 3-x) 3n+1材料旋涂于空穴注入层132上，厚度约为50nm，并以70℃退火5min，以得到发光层131；接着，成型电子注入层133以及第二透明电极140，具体地，将TPBi电子注入层材料、电子注入界面LiF以及超薄Al电极依次以蒸镀的方式沉积在钙钛矿发光层131上，厚度分别为35nm、1nm及10nm；然后，将第一荧光粉层150(CsPbBr 0.5I 2.5)以旋涂方式沉积于超薄Al电极上，厚度约为100nm；并将第二荧光粉层160(CsPbBr 2.5I 0.5)以旋涂方式沉积于玻璃衬底上，厚度约为50nm，完成制备步骤。另外，如果不沉积第一荧光粉层150、第二荧光粉层160，则得到的是倒置结构的钙钛矿蓝光LED芯片。
下面结合图3b、图8a-8b所示，对倒置结构的钙钛矿蓝光LED芯片与本具 体实施例的钙钛矿三色白光LED芯片100的电学特性及外量子效率进行比较。图8a所示为钙钛矿蓝光及钙钛矿三色白光LED芯片的电压-电流密度曲线，从图8a可见，第一荧光粉层150以及第二荧光粉层160的沉积几乎不会影响钙钛矿蓝光LED芯片的电学特性。
另外，从图8b所示的钙钛矿蓝光及钙钛矿三色白光LED芯片的电流密度-外量子效率曲线可看出，由于钙钛矿发光层131的折射率(约2.5)远大于TPBi电子注入层133的折射率(约1.7)，全反射同样极大地限制了光子的出射，导致了钙钛矿蓝光钙钛矿LED芯片的外量子效率较低(约为3.5％)；然而，当引入第一荧光粉层150后，由于对全反射时所产生的隐失波进行了利用，通过吸收隐失波再发出荧光的方式，提高了芯片内部光子的实际利用率，使得芯片的外量子效率提高到4.8％，获得了将约37％的提高。
值得注意的是，该效率提高幅度不如前述量子点双色白光LED芯片100中的效率提高幅度，其原因是引入了处于远场的第二荧光粉层160，不能对器件效率做出正向贡献，反而由于其荧光量子效率不足100％而导致对芯片外量子效率有负向贡献，但本具体实施例之钙钛矿三色白光LED芯片的外量子效率仍远高于现有技术中的钙钛矿白光LED芯片。
下面结合图3b、图9a-9b所示，由于本具体实施例之钙钛矿蓝光及钙钛矿三色白光LED芯片的发光由蓝光(芯片发出)、红光(第一荧光粉层150发出)以及绿光(第二荧光粉层160发出)组成，如图9a所示，通过三基色原理构成了三色白光，并且该钙钛矿三色白光LED芯片的色坐标处于(0.29,0.37)位置，如图9b所示，表明其光色为较纯正的白光。
综上，由于本申请的薄膜型白光LED芯片100，其包括依次设置的透明衬底110、第一透明电极120、发光结构130、第二透明电极140及第一荧光粉层150，其中，发光结构130包括发光层131及设于其两侧的电子注入层133及空穴注入层132，且电子注入层133与第二透明电极140的总厚度(倒置结构)或空穴注入层132与第二透明电极140的总厚度(正置结构)小于所述发光层131的一个发光波长长度。首先，由于将现有技术中的反射金属电极替换为第二透明电极140，因此能够让发光层131所发出的光子在该方向上不会进行完全反射， 而是有机会渗透到第一荧光粉层150；其次，通过电子注入层133与第二透明电极140的总厚度(倒置结构)或空穴注入层132与第二透明电极140的总厚度(正置结构)小于发光层131的一个发光波长长度的设置，使得因全反射所产生的隐失波能够渗透至第一荧光粉层150而被第一荧光粉层150所吸收，通过吸收隐失波再发出荧光的方式，提高了芯片内部光子的实际利用率，使得LED芯片的整体外量子效率提高，进而降低照明能耗，同时能够保证白光发射，并且生产成本低。
以上所揭露的仅为本申请的优选实施例而已，当然不能以此来限定本申请之权利范围，因此依本申请申请专利范围所作的等同变化，仍属本申请所涵盖的范围。

Claims (10)

  1. 一种薄膜型白光LED芯片，其特征在于，包括依次设置的透明衬底、第一透明电极、发光结构、第二透明电极及第一荧光粉层，其中，所述发光结构包括发光层及设于其两侧的电子注入层及空穴注入层，且所述电子注入层与所述第二透明电极的总厚度或所述空穴注入层与所述第二透明电极的总厚度小于所述发光层的一个发光波长长度。
  2. 如权利要求1所述的薄膜型白光LED芯片，其特征在于，所述发光层包括发光波长在200nm-430nm的紫光发光材料或发光波长在430nm-500nm的蓝光发光材料。
  3. 如权利要求2所述的薄膜型白光LED芯片，其特征在于，所述发光结构包括依次设置的所述空穴注入层、所述发光层及所述电子注入层，所述电子注入层与所述第二透明电极邻接，且所述电子注入层的厚度小于200nm，所述空穴注入层的厚度小于1000nm。
  4. 如权利要求2所述的薄膜型白光LED芯片，其特征在于，所述发光结构包括依次设置的所述电子注入层、所述发光层及所述空穴注入层，所述空穴注入层与所述第二透明电极邻接，且所述空穴注入层的厚度小于200nm，所述电子注入层的厚度小于1000nm。
  5. 如权利要求1-4任一项所述的薄膜型白光LED芯片，其特征在于，所述电子注入层、所述空穴注入层的材料均为有机聚合物和小分子、金属氧化物、无机半导体材料、有机无机复合物中的至少一种，所述发光层的光材料为有机发光材料、量子点和纳米晶材料、无机发光材料、有机无机杂化发光材料中的至少一种。
  6. 如权利要求1所述的薄膜型白光LED芯片，其特征在于，所述第二透明电极的厚度小于100nm，所述第一透明电极的厚度小于1000nm，且所述第二透 明电极、所述第一透明电极的材料均为超薄金属膜、图案化金属膜、金属纳米线、金属纳米棒、金属纳米颗粒、有机聚合物及小分子、金属氧化物、有机无机复合物中的至少一种。
  7. 如权利要求1所述的薄膜型白光LED芯片，其特征在于，还包括第二荧光粉层，所述第二荧光粉层设于所述透明衬底的远离所述第一透明电极的一侧，且所述第一荧光粉层、所述第二荧光粉层的厚度均小于1mm。
  8. 如权利要求7所述的薄膜型白光LED芯片，其特征在于，所述第一荧光粉层、所述第二荧光粉层均包括发光波段在430nm-500nm的蓝光荧光材料、发光波段在500nm-560nm的绿光荧光材料、发光波段在560nm-600nm的黄光荧光材料、发光波段在600nm-780nm的红光荧光材料中的至少一种。
  9. 如权利要求7所述的薄膜型白光LED芯片，其特征在于，所述第一荧光粉层、所述第二荧光粉层的荧光材料均为有机荧光材料、量子点和纳米晶材料、无机荧光材料、有机无机杂化荧光材料中的至少一种。
  10. 如权利要求7-9任一项所述的薄膜型白光LED芯片，其特征在于，所述第一透明电极、所述发光层、所述电子注入层、所述及空穴注入层、所述第二透明电极、所述第一荧光粉层及所述第二荧光粉层均可通过气相沉积、溅射、旋涂、刮涂、蒸镀、喷墨打印、滴涂、卷对卷印刷、狭缝涂布、丝网印刷、喷涂或机械印压的方式成型。
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US20070029560A1 (en) * 2005-08-04 2007-02-08 Jung-Chieh Su Light-emitting devices with high extraction efficiency
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