A method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties

Abstract

This invention relates to a method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties. The method first fabricates a top-emitting QLED device with a F-P-like microcavity structure. The core of the method lies in actively controlling the spacing between emitting quantum dots (donors and acceptors) by doping a mixed red, green, and blue quantum dot emitting layer with non-emitting quantum dots of different concentrations or sizes. Simultaneously, the thickness of each functional layer of the device is designed and optimized according to the microcavity resonance interference formula to achieve resonance enhancement at specific wavelengths. By measuring and comparing the changes in the time-resolved fluorescence spectrum curves of the device under different quantum dot spacings, and combining this with the Foster energy transfer efficiency formula for calculation and analysis, the enhancement effect of the microcavity structure on the energy transfer process is revealed and verified. This invention provides a direct and effective research method for in-depth exploration of the interaction mechanism between microcavity structure and Foster energy transfer.

Description

Technical Field

[0001] This invention relates to a method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties. Background Technology

[0002] In normal full-color or dual-color QLED devices, the quantum dot emitting layer, after spin coating, film stretching and transfer (LB-TB), or patterning, typically forms a dense quantum dot film, resulting in a distance of 10nm-50nm between quantum dots. This distance coincides with the Foster radius of the Foster energy transfer (FRET) that occurs between the donor and acceptor, leading to FRET. Currently, the international consensus is that FRET is mainly composed of three elements: 1. Overlapping emission spectra of the donor and acceptor; 2. The distance between the donor and acceptor must be within the Foster radius; 3. The directions of dipole radiation from the donor and acceptor must be as coupled or parallel as possible. Some experiments have shown that FRET facilitates the conversion of non-radiative recombination exciton energy in the emitting layer into radiative recombination, which is significant for improving the performance of QLED devices. Furthermore, some literature and experiments have found that microcavity structure has a significant impact on FRET, but the underlying mechanism is not clearly explained. However, elucidating the influence of microcavity structure on FRET is of great research significance for studying the performance of QLED devices. Summary of the Invention

[0003] The purpose of this invention is to study the influence of microcavity structure on Foster energy transfer in QLED devices using optical property research methods, and to provide a method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties. This method involves adding non-luminescent quantum dot materials of different radii to the light-emitting layer of the original QLED device and optimizing the structural thickness to prepare a QLED top-emitting device with a microcavity structure.

[0004] To achieve the above objectives, the technical solution of the present invention is: a method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties, comprising:

[0005] A top-emitting QLED device with a microcavity structure is fabricated. The structure of the device includes, in sequence: an ITO substrate with a light-reflecting layer, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode.

[0006] In the quantum dot emitting layer, non-luminescent quantum dot material is doped. By adjusting the doping concentration or size of the non-luminescent quantum dot material, the distance R between the luminescent quantum dot donor and acceptor in the quantum dot emitting layer can be controlled.

[0007] Based on the microcavity resonance condition formula, the thickness of each functional layer in the QLED device is optimized.

[0008] After the QLED device was fabricated, its time-resolved fluorescence spectrum (TRPL) was measured. The influence of the microcavity structure on energy transfer was analyzed based on the Foster resonance energy transfer (FRET) efficiency formula, which is:

[0009]

[0010] in, The Foster radius is calculated using the following formula:

[0011]

[0012] in, For dipole orientation parameters, Let be the refractive index of the medium. For quantum yield, It is the integral of the spectral overlap between the donor excitation spectrum and the acceptor absorption spectrum.

[0013] Furthermore, the formula for the microcavity resonance condition is as follows:

[0014]

[0015]

[0016]

[0017] in, The vertical distance from the light-emitting layer to the top cathode. The vertical distance from the light-emitting layer to the bottom anode. This refers to the phase change when light reaches the top cathode and is reflected. This refers to the phase change when light reaches the bottom anode and is reflected. The emission angle of the light-emitting point. It is a natural number, with values ​​from 0 to ∞.

[0018] Furthermore, in the ITO substrate with the light-reflecting layer, the light-reflecting layer material is selected from any one or a combination of Ag, Al, and IZO.

[0019] Furthermore, the material of the hole injection layer is any one of poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS), molybdenum oxide, nickel oxide, and cuprous thiocyanate.

[0020] Furthermore, the material of the hole transport layer is any one or a combination of polymer TFB, Poly:TPD, and PVK.

[0021] Furthermore, the non-luminescent quantum dot material is any one or a combination of silicon quantum dots, rare earth quantum dots, silicon dioxide quantum dots, lead oxide quantum dots, and mercury sulfide quantum dots.

[0022] Furthermore, the luminescent quantum dot material in the luminescent layer is any one or a combination of CdS, CdSe, InP, CuInS, and PbSe.

[0023] Furthermore, the material of the electron transport layer is any one or a combination of ZnO, TiO2, SnO2, LiZnO, and MgZnO.

[0024] Furthermore, the cathode material is any one or a combination of Au, Ag, Al, and IZO.

[0025] Furthermore, the thickness range of each layer in the fabricated QLED device is as follows: the ITO substrate with light-reflecting layer is 80nm-170nm, the hole injection layer is 20nm-40nm, the hole transport layer is 10nm-40nm, the quantum dot light-emitting layer is 10nm-40nm, the electron transport layer is 40nm-100nm, and the cathode is 15nm-100nm.

[0026] Compared with the prior art, the present invention has the following beneficial effects: Attached Figure Description

[0027] Figure 1 The device structure prepared according to the present invention.

[0028] Figure 2 It is a hybrid quantum dot light-emitting layer structure.

[0029] In the figure, 1 is the substrate light-reflecting layer, 2 is the conductive anode layer, 3 is the hole injection layer, 4 is the hole transport layer, 5 is the hybrid quantum dot light-emitting layer, 6 is the electron transport layer, and 7 is the cathode. Detailed Implementation

[0030] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0031] This invention provides a method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties, comprising:

[0032] A top-emitting QLED device with a microcavity structure is fabricated. The structure of the device includes, in sequence: an ITO substrate with a light-reflecting layer, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode.

[0033] In the quantum dot emitting layer, non-luminescent quantum dot material is doped. By adjusting the doping concentration or size of the non-luminescent quantum dot material, the distance R between the luminescent quantum dot donor and acceptor in the quantum dot emitting layer can be controlled.

[0034] Based on the microcavity resonance condition formula, the thickness of each functional layer in the QLED device is optimized. The microcavity resonance condition formula is as follows:

[0035]

[0036]

[0037]

[0038] in, The vertical distance from the light-emitting layer to the top cathode. The vertical distance from the light-emitting layer to the bottom anode. This refers to the phase change when light reaches the top cathode and is reflected. This refers to the phase change when light reaches the bottom anode and is reflected. The emission angle of the light-emitting point. It is a natural number, with values ​​from 0 to ∞;

[0039] After the QLED device was fabricated, its time-resolved fluorescence spectrum (TRPL) was measured. The influence of the microcavity structure on energy transfer was analyzed based on the Foster resonance energy transfer (FRET) efficiency formula, which is:

[0040]

[0041] in, The Foster radius is calculated using the following formula:

[0042]

[0043] in, For dipole orientation parameters, Let be the refractive index of the medium. For quantum yield, It is the integral of the spectral overlap between the donor excitation spectrum and the acceptor absorption spectrum.

[0044] The following is a detailed implementation process of the present invention.

[0045] like Figure 1 As shown, the device structure includes: a substrate light-reflecting layer 1, a conductive anode layer 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7.

[0046] Fabrication steps for high-resolution microcavity devices:

[0047] 1) Spin-coat poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS) or one of molybdenum oxide, nickel oxide, cuprous thiocyanate, and other hole injection layer materials onto an ITO substrate with a light-reflecting layer.

[0048] 2) Spin-coat any one or a combination of TFB, Poly:TPD, PVK, or hole transport layer materials onto the hole injection layer.

[0049] 3) Preparation of mixed solutions or materials of non-luminescent quantum dots and luminescent quantum dots

[0050] 4) Spin-coating a mixture of luminescent quantum dots and luminescent quantum dot solutions or materials onto the hole transport layer.

[0051] 5) Spin-coating an electron transport layer material of any one or a combination of ZnO, TiO2, SnO2, LiZnO, and MgZnO onto the quantum dot luminescent layer.

[0052] 6) A semi-transparent or transparent cathode film made of any one or a combination of Au, Ag, Al, IZO is formed by vapor deposition or plasma sputtering in the electron transport layer.

[0053] The fabrication steps of high-resolution devices with microcavity structures also include: optimizing the structural thickness of the high-resolution device to fabricate a QLED high-resolution top-emitting device with a microcavity structure.

[0054] Microcavity resonance-enhanced interference formula:

[0055]

[0056]

[0057]

[0058] in The vertical distance from the light-emitting layer to the top cathode. This is the vertical distance from the light-emitting layer to the bottom anode. This refers to the phase change when light reaches the top cathode and is reflected. This represents the phase change when light reaches the bottom anode and is reflected. The emission angle of the light source is denoted as . The natural numbers range from 0 to infinity.

[0059] Formulas (1) and (2) represent wide-angle interference, while formula (3) represents multi-beam interference. When the above formulas are used... When the value is 1, the formula represents first-order interference resonance enhancement; when the value is 2, it represents second-order interference resonance enhancement.

[0060] According to the above formula, the thickness of high-resolution QLED devices based on microcavity structures can be controlled, and the microcavity effect is optimal when the first-order interference resonance is enhanced.

[0061] To investigate whether the Purcell effect modulates the FRET phenomenon, we used non-luminescent quantum dots of varying concentrations and sizes doped into the emissive layer to control the distance between the donor and acceptor. We then investigated whether the Purcell effect affects the optical properties of FRET in a QLED device with a microcavity structure. See details... Figure 2 .

[0062] The FRET efficiency formula is as follows:

[0063]

[0064] in The distance between the donor and the recipient. The specific expression for the Foster radius is as follows:

[0065]

[0066] For dipole orientation parameters, Let be the refractive index of the medium. For quantum yield, It is the integral of the spectral overlap between the donor excitation spectrum and the acceptor absorption spectrum.

[0067] The preferred thickness range for the device structure fabricated using the method in this example is as follows:

[0068] The Figure 1 The combined structure of the light-reflecting layer and the conductive anode layer of the substrate has a density range of 80nm-170nm.

[0069] The thickness of the hole injection layer ranges from 20nm to 40nm.

[0070] The hole transport layer has a thickness ranging from 10 nm to 40 nm.

[0071] The thickness of the quantum dot luminescent layer ranges from 10 nm to 40 nm.

[0072] The thickness of the electron transport layer ranges from 40nm to 100nm.

[0073] The thickness of the cathode material ranges from 15 nm to 100 nm.

[0074] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties, characterized in that, include: A top-emitting QLED device with a microcavity structure is fabricated. The structure of the device includes, in sequence: an ITO substrate with a light-reflecting layer, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode. In the quantum dot emitting layer, non-luminescent quantum dot material is doped. By adjusting the doping concentration or size of the non-luminescent quantum dot material, the distance R between the luminescent quantum dot donor and acceptor in the quantum dot emitting layer can be controlled. Based on the microcavity resonance condition formula, the thickness of each functional layer in the QLED device is optimized. After the QLED device was fabricated, its time-resolved fluorescence spectrum (TRPL) was measured. The influence of the microcavity structure on energy transfer was analyzed based on the Foster resonance energy transfer (FRET) efficiency formula, which is: in, The Foster radius is calculated using the following formula: in, For dipole orientation parameters, Let be the refractive index of the medium. For quantum yield, It is the integral of the spectral overlap between the donor excitation spectrum and the acceptor absorption spectrum.

2. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The formula for the microcavity resonance condition is: in, The vertical distance from the light-emitting layer to the top cathode. The vertical distance from the light-emitting layer to the bottom anode. This refers to the phase change when light reaches the top cathode and is reflected. This refers to the phase change when light reaches the bottom anode and is reflected. The emission angle of the light-emitting point. It is a natural number, with values ​​from 0 to ∞.

3. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, In the ITO substrate with the light-reflecting layer, the light-reflecting layer material is selected from any one or a combination of Ag, Al, and IZO.

4. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The material of the hole injection layer is any one of poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS), molybdenum oxide, nickel oxide, and cuprous thiocyanate.

5. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The material of the hole transport layer is any one or a combination of polymers TFB, Poly:TPD, and PVK.

6. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The non-luminescent quantum dot material is any one or a combination of silicon quantum dots, rare earth quantum dots, silicon dioxide quantum dots, lead oxide quantum dots, and mercury sulfide quantum dots.

7. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The luminescent quantum dot material in the luminescent layer is any one or a combination of CdS, CdSe, InP, CuInS, and PbSe.

8. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The material of the electron transport layer is any one or a combination of ZnO, TiO2, SnO2, LiZnO, and MgZnO.

9. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The cathode material is any one or a combination of Au, Ag, Al, and IZO.

10. The method for analyzing the influence of microcavity structure on Foster energy transfer in QLED devices based on optical properties according to claim 1, characterized in that, The QLED device fabricated has the following layer thicknesses: the ITO substrate with light-reflecting layer is 80nm-170nm, the hole injection layer is 20nm-40nm, the hole transport layer is 10nm-40nm, the quantum dot light-emitting layer is 10nm-40nm, the electron transport layer is 40nm-100nm, and the cathode is 15nm-100nm.

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