Long-life cadmium-free quantum dot film and application thereof

Abstract

The application relates to a long-life cadmium-free quantum dot film, a preparation method and application thereof, and more particularly provides an improved in-situ preparation method of a perovskite quantum dot composite film, which selects formic acid 2-hydroxyethyl ammonium as an additive, improves dispersibility, reduces agglomeration, improves luminous efficiency, improves the thermal stability of the film, and has a long service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light-emitting materials, and relates to a long-life cadmium-free quantum dot film, in particular to a preparation method of a perovskite quantum dot composite film synthesized in situ. BACKGROUND

[0002] The quantum dot composite film is a multifunctional optical composite film with the functions of color gamut enhancement, brightness enhancement, light diffusion, etc.

[0003] A quantum dot in-situ preparation technology was developed by Professor Zhong Haizheng's team of Beijing University of Technology, and perovskite materials were directly prepared in a polymer matrix by using the solution processing characteristics of perovskite materials (Adv. Mater. 2016, 28, 9163-9168). In this method, the polymer PVDF is dissolved in the mixture of quantum dot preparation raw materials and solvents, greatly simplifying the preparation process. Chinese patent CN109438599A discloses a method for directly obtaining a perovskite quantum dot composite film in an “in-situ preparation” manner by dispersing perovskite raw material components and additives in an ultraviolet light-curable adhesive and curing the same by ultraviolet light irradiation. In the whole preparation process, no organic solvent is used, further simplifying the operation, but the light-emitting efficiency is low, only about 40%, which still needs to be optimized and improved. SUMMARY

[0004] The present application aims to provide a long-life cadmium-free quantum dot film, which can be an improved perovskite quantum dot composite film.

[0005] The present application also provides an improved in-situ preparation method of a perovskite quantum dot composite film, which selects 2-hydroxyethylammonium formate as an additive to improve dispersibility, reduce agglomeration, improve light-emitting efficiency, and improve the thermal stability of the film.

[0006] The specific technical solutions adopted are as follows:

[0007] A preparation method of a perovskite quantum dot composite film synthesized in situ, comprising the following steps:

[0008] S1, stirring and mixing perovskite raw material components and ultraviolet light-curable adhesive, and then adding an additive to disperse the system uniformly to obtain a film-forming glue solution;

[0009] The additive is 2-hydroxyethylammonium formate.

[0010] The perovskite raw material components include a perovskite raw material first component and a perovskite raw material second component.

[0011] The molecular formula structure of the perovskite raw material first component is AX. A is an ammonium ion or a metal ion, for example, CH3NH3 +H2N-CH=NH2 + (CH3)4N + Cs + X is a halogen ion, such as Cl - Br - I - .

[0012] The molecular formula of the second component of the perovskite raw material is BX2. Wherein, B is Pb 2+ Sn 2+ X is a halogen ion, such as Cl - Br - I - .

[0013] The ratio of the amount of substance of the first component of the perovskite raw material to the second component of the perovskite raw material is 0.8:1-2.0:1, preferably 0.8:1-1.0:1.

[0014] The ratio of the amount of substance of the additive to the second component of the perovskite raw material is 0.2:1-0.5:1.

[0015] The ultraviolet light curing adhesive is composed of a prepolymer, an active monomer and a photoinitiator.

[0016] The weight ratio of the prepolymer, the active monomer and the photoinitiator is 0.5-1.5:1:0.01-0.08.

[0017] The functionality of the prepolymer is 2-6, and the viscosity at room temperature is 3000-40000 CPS. Preferably, it is one or a mixture of several of polyurethane acrylate prepolymer, polyether acrylate prepolymer.

[0018] The active monomer is one or a mixture of several of monofunctional acrylate diluent monomer, difunctional diluent monomer, multifunctional diluent monomer. Preferably, it is at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate.

[0019] The photoinitiator is a photoinitiator for initiating free radical polymerization. Preferably, it is one or several of 1-hydroxycyclohexyl phenyl ketone, methyl o-benzoylbenzoate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,2-dimethyloxymethyl-2-phenylphenylethanone, (2,4,6-trimethylbenzoyl chloride) diphenyl phosphine oxide, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, benzophenone, 2-methylbenzophenone.

[0020] S2, coating the film-forming glue solution on the base material, curing by ultraviolet light irradiation to obtain the perovskite quantum dot composite film.

[0021] The coating method includes spin coating, blade coating, roller coating, spraying, printing, dipping and casting.

[0022] The base material is preferably PET, PPMA or glass.

[0023] The application also provides a perovskite quantum dot composite film for optical composite film.

[0024] The application has the following advantages:

[0025] The in-situ preparation method of the perovskite quantum dot composite film provided by the application uses formic acid 2-hydroxyethyl ammonium ion liquid as an additive, which can act as a dispersant and a cationic ligand, and the 2-hydroxyethyl ammonium ion can form mixed cation quantum dots as a cationic ligand, thereby improving dispersibility, reducing agglomeration, improving luminous efficiency, improving the thermal stability of the film, and prolonging the service life. DETAILED DESCRIPTION

[0026] The technical solutions of the application will be described in detail below in combination with specific embodiments. It should be noted that the described embodiments are only part of the embodiments of the application, not all embodiments.

[0027] Example 1

[0028] Preparation method of the perovskite quantum dot composite film:

[0029] S1, mixing and stirring formamidinium iodide, PbI2 and ultraviolet light curing glue uniformly, then adding formic acid 2-hydroxyethyl ammonium thereto, and ultrasonic dispersion for 5s to obtain a film-forming glue solution.

[0030] The added mass of formamidinium iodide and PbI2 is 0.13g and 0.45g respectively, and the added amount of formic acid 2-hydroxyethyl ammonium is 0.08g.

[0031] Preparation of ultraviolet light curing glue: uniformly mixing 18g of polyurethane acrylate, 10g of butyl acrylate, 10g of pentaerythritol triacrylate and 0.5g of benzophenone.

[0032] S2, spin coating the film-forming glue solution of S1 on the PET film, curing by ultraviolet light irradiation to obtain the perovskite quantum dot composite film.

[0033] The spin coating speed is set to 600rpm, the volume of the film-forming glue solution added each time is 0.3mL, and a high-pressure mercury lamp is used to irradiate at an energy of 1000mj / cm 2 for 30s.

[0034] Test:

[0035] The composite film was characterized: the emission spectrum and luminescent efficiency were tested by a fluorescence spectrophotometer, the luminescent wavelength was determined to be 536 nm, and the half-peak width was 18 nm; the quantum yield was measured to be 72% at an excitation wavelength of 435 nm.

[0036] Example 2

[0037] Preparation method of perovskite quantum dot composite film:

[0038] S1, mix and stir phenethylamine bromide, PbBr2 and ultraviolet light curing glue until uniform, then add 2-hydroxyethylammonium formate to the mixture, ultrasonic for 5s to make the system uniformly dispersed, and obtain a film forming glue solution.

[0039] Among them, the added mass of phenethylamine bromide and PbBr2 is 0.16g and 0.37g respectively, and the added amount of 2-hydroxyethylammonium formate is 0.08g.

[0040] Preparation of ultraviolet light curing glue: mix 15g of polyurethane acrylate, 9g of butyl acrylate, 9g of pentaerythritol triacrylate and 0.4g of benzophenone uniformly.

[0041] S2, spin coating the film forming glue solution of S1 on the PET film, curing by ultraviolet light irradiation, and obtaining a perovskite quantum dot composite film.

[0042] The spin coating speed is set to 600rpm, the volume of the film forming glue solution added each time is 0.3mL; a high pressure mercury lamp is used to irradiate for 40s with an energy of 1000mj / cm 2 .

[0043] Test:

[0044] The composite film was characterized: the emission spectrum and luminescent efficiency were tested by a fluorescence spectrophotometer, the luminescent wavelength was determined to be 536 nm, and the half-peak width was 18 nm; the quantum yield was measured to be 72% at an excitation wavelength of 435 nm.

[0045] Comparative example 1

[0046] According to the method of example 1, 1-butyl-3-methylimidazolium hexafluorophosphate is selected as the additive, and other conditions are the same as those of example 1. The quantum yield is tested to be 45% under the same conditions.

[0047] Example 3

[0048] The thermal stability test was performed by placing the thin films prepared in Examples 1-2 and Comparative Example 1 in an 80°C constant temperature oven for 72 hours. The results showed that the quantum yields of Examples 1-2 and Comparative Example 1 decreased to 95%, 93%, and 81% of the initial values, respectively.

[0049] As can be seen from the above examples and comparative examples, the present application improves the luminescent properties of quantum dots, especially the quantum yield, and also improves the thermal stability and the long lifetime by selecting a suitable type of ionic liquid as an additive and in-situ polymerizing with specific perovskite raw material components.

Claims

1. A method for preparing an in-situ synthesized perovskite quantum dot composite film, comprising the following steps: S1. Mix formamidine iodide, PbI2 and UV-curable adhesive and stir evenly. Then add 2-hydroxyethylammonium formic acid and sonicate for 5 seconds to disperse the system evenly to obtain film-forming adhesive solution. The amounts of formamidinium iodide and PbI2 added were 0.13 g and 0.45 g, respectively, and the amount of 2-hydroxyethylammonium formate added was 0.08 g. Preparation of UV-curable adhesive: Mix 18g of polyurethane acrylate, 10g of butyl acrylate, 10g of pentaerythritol triacrylate, and 0.5g of benzophenone evenly. S2. Spin-coat the film-forming adhesive solution of S1 onto the PET film and cure it by ultraviolet light irradiation to obtain a perovskite quantum dot composite film. The spin coating speed was set to 600 rpm, and the volume of film-forming adhesive added for each spin coating was 0.3 mL; a high-pressure mercury lamp was used at 1000 mJ / cm². 2 Irradiate energy for 30 seconds.

2. The perovskite quantum dot composite film prepared by the preparation method according to claim 1.