CN113451484B - Display-oriented light conversion efficiency calculation method for monochromatic quantum dot color conversion layer - Google Patents
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Abstract
The invention relates to a light conversion efficiency calculation method for a display-oriented monochromatic quantum dot color conversion layer, which comprises the following steps of: s1, acquiring initial parameters of a quantum dot light-color conversion layer; s2, dividing logic channels of the color conversion layer according to different wavelengths or frequencies of light; s3, constructing a theoretical relation model among monochromatic light converted by the quantum dot light-color conversion layer, the thickness of the diaphragm and the concentration of the quantum dots based on the quantum dot color conversion logic channel; s4, acquiring the optimal parameters of the film thickness and the concentration of the quantum dot light color conversion layer according to a theoretical relationship model; and S5, establishing a theoretical relation among the light conversion efficiency, the membrane thickness and the quantum dot concentration. The invention can accurately and efficiently obtain the light-emitting optical performance parameters of the quantum dot light color conversion layer, such as the light-emitting intensity and the light conversion efficiency of the converted light, and obtain the concentration of the quantum dots or the thickness parameter of the light color conversion layer when the conversion light conversion efficiency is maximum.
Description
Technical Field
The invention relates to the field of novel display, in particular to a light conversion efficiency calculation method for a single-color quantum dot color conversion layer for display.
Background
The term "quantum dots" was created in 1986 and was first discovered by Alexey Ekimov and Louis Brus in glass matrix and colloidal solutions. Quantum Dots (Quantum Dots) refer to semiconductor nanocrystalline materials with Quantum confinement effect in three dimensions of space, also referred to as "artificial atoms". The quantum dots are mostly quasi-zero-dimensional nano materials composed of II-VI group or III-V group elements, the sizes of three dimensions of the quantum dots are all 1-10 nm, and the quantum dots are just like tiny point-shaped objects in appearance. The electron transport in the quantum dots is limited, the electron mean free path is short, the electron locality and coherence are enhanced, and therefore the quantum confinement effect is particularly remarkable. Because electrons and holes are confined by quanta, a continuous energy band structure is changed into a discrete energy level structure, and therefore the advantages of narrow light-emitting spectrum (20-30 nm), high color purity, wide color gamut and the like are achieved. The quantum dots with different sizes have different electron and hole quantum confinement degrees, and the discrete energy level structures with molecular characteristics are different due to different sizes of the quantum dots, so that the quantum dots with different sizes can emit fluorescence with different wavelengths, namely light with various colors after being excited by external energy. The combination of quantum dots and a display technology becomes one of key points and hot points of research in the display field, so that the color expression capability of the display device can be greatly improved, and the utilization rate of the display device to light rays can be greatly improved. The quantum dot light-color conversion layer not only can help the display to realize wide color gamut, but also has higher light conversion efficiency, and has wide application prospect on display devices such as liquid crystal displays, micro-LEDs, mini-LEDs, blue light OLEDs and the like. However, the current patterning preparation technology of the quantum dot film still has some key technical problems to be solved, including white balance of emergent light color, utilization rate of light effect, incident light transmittance, service life of the quantum dot film and the like. Therefore, the design of the quantum dot light color conversion layer is one of the key technologies of the backlight module. At present, the existing papers and researches select the thickness and concentration of the quantum dot film through simulation so as to meet the requirements of high light efficiency utilization rate of the quantum dot, low incident light transmittance and the like. Without specific theoretical exploration, this simulation approximation actually has a large impact on the overall effect. In summary, it is difficult for the prior art to intuitively determine the thickness of the quantum dot light-color conversion layer and the quantum dot concentration parameter when the conversion efficiency of the converted light is the maximum, and in order to solve the problem, it is necessary to provide a technical basis and a theoretical guidance method for accurately and efficiently calculating the design of the thickness of the quantum dot light-color conversion layer and the quantum dot concentration parameter.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method for calculating light conversion efficiency of a monochromatic quantum dot color conversion layer for display, which can accurately and efficiently obtain light-emitting optical performance parameters of the quantum dot color conversion layer, including converted light-emitting intensity, light conversion efficiency, and the like, and obtain a quantum dot concentration or a thickness parameter of the color conversion layer when the converted light conversion efficiency is the maximum.
In order to realize the purpose, the invention adopts the following technical scheme:
a light conversion efficiency calculation method for a display-oriented monochromatic quantum dot color conversion layer comprises the following steps:
s1, acquiring initial parameters of a quantum dot light-color conversion layer;
s2, dividing logic channels of the color conversion layer according to different wavelengths or frequencies of light;
s3, constructing a theoretical relation model among monochromatic light converted by the quantum dot light-color conversion layer, the thickness of the diaphragm and the concentration of the quantum dots on the basis of the quantum dot color conversion logic channel;
and S4, acquiring the optimal parameters of the film thickness and the concentration of the quantum dot light color conversion layer according to the theoretical relation model.
And S5, establishing a theoretical relation among the light conversion efficiency, the membrane thickness and the quantum dot concentration.
Further, the initial parameters comprise monochromatic quantum dot light emission spectrum parameters, quantum dot color conversion layer film thickness and quantum dot concentration parameters, molar absorption coefficients of a base medium material forming the color conversion layer respectively relative to incident light and converted light, and light intensity parameters of a Lambert surface light source.
Further, the logic channel division specifically includes: and respectively decomposing the color conversion layer mixed with the monochromatic quantum dots into a pure incident light logic channel 1 and a quantum dot color conversion logic channel 2 from a logic level.
Further, the theoretical relationship model includes:
when the concentration of the quantum dots is uniform and fixed, the relation that the light intensity of red/green monochromatic light generated after the quantum dots are excited by incident light changes along with the thickness of the film is obtained;
when the concentration of the quantum dots is uniform and the thickness is fixed, the relation that the light intensity of red/green monochromatic light generated after the quantum dots are excited by incident light changes along with the concentration of the quantum dots is obtained;
when the concentration of the quantum dots is uniform and variable, the relation of the light intensity of the converted monochromatic light with the change of the film thickness and the concentration is deduced.
Further, the relationship between the light intensity of the converted monochromatic light and the change of the film thickness and concentration is obtained as follows: sequentially calculating the relation of the incident light intensity I 'changing along with the film thickness h, the relation of the incident light intensity I' changing along with the film thickness h and the quantum dot concentration c, and the relation of the converted monochromatic light intensity I changing along with the film thickness h according to the determined initial parameters of the quantum dot light-color conversion layer; and further obtaining the relation that the light intensity I of the converted monochromatic light changes along with the film thickness h and the quantum dot concentration c.
Further, the calculating of the relationship between the incident light intensity I' and the variation of the film thickness h and the concentration c respectively includes:
according to the Buerg-Lambert law: when the concentration of the quantum dots in the photochromic conversion layer is fixed, the light intensity after the light passes through a certain medium is as follows:
I′(h)＝I 0 e -αh
in the formula I 0 The initial incident light intensity of the Lambert surface light source; h is the thickness of the quantum dot light-color conversion layer; alpha is a normal constant, which is the absorption coefficient of the medium for the incident light.
According to the Buerger-Lambert law: when the thickness of the light color conversion layer is fixed and the concentration of the quantum dots is uniformly changed, the light intensity of light passing through the preset medium is as follows:
I′(c)＝I 0 e -αc
in the formula, c is the concentration of quantum dots in the photochromic conversion layer;
further, the relation that the incident light intensity I' changes with the film thickness h and the quantum dot concentration c is calculated, specifically, according to the lambert-beer law:
A＝lg(1/T)＝εhc
wherein A is absorbance, T is transmittance, and is emergent light intensity I' and incident light intensity I 0 E is the molar absorption coefficient of the material with respect to the incident light, c is the concentration of the light-absorbing substance in mol/L, h is the thickness of the absorbing layer in cm;
let T = I'/I 0 Substituting the equation to obtain:
I′(h，c)＝I 0 ×10 -εhc
i.e. the relation of the incident light intensity I' varying with the film thickness h and the quantum dot concentration c.
Further, the calculating of the relationship between the converted monochromatic light intensity I and the change of the film thickness h specifically includes:
the exiting converted light has the following formula:
I(h)＝I in (h)-I out (h)
wherein I (h) represents the intensity of the emitted converted light, I in (h) Indicating the intensity of the generated converted light, I out (h) A converted light intensity representing a loss;
the emitted converted light intensity is equal to the generated converted light intensity minus the loss, and the two sides of the above formula are derived to obtain a balance formula:
setting the proportionality coefficient as eta, then I in Can be expressed as:
I in (h)＝kηI 0 e -αh
where k is a proportionality coefficient representing the intensity of incident light into the channel 2 and the total intensity of incident light I from the actual color conversion layer 0 The ratio of (A) to (B); eta is conversion efficiency which represents the conversion efficiency of converting the quantum dots at the current position into the monochromatic light;
the loss satisfies that the loss rate of the converted light under the unit length is in direct proportion to the light intensity of the converted light at the current position in the film, and the absorption coefficient is beta, so that the following formula can be obtained:
I out (h)＝I in ×e -βh
will I in (h) And I out (h) When the above-mentioned equilibrium formula is substituted with the above-mentioned relational expression, since the generation of converted light is not excited when the film thickness is 0, the boundary conditions are:
I(0)＝0
the solution to this equation is then:
I(h)＝kηI 0 [e -αh -e -(α+β)h ]
namely a relation formula of the light intensity I of the converted monochromatic light changing along with the film thickness h; where k is a proportionality coefficient representing the intensity of incident light into the channel 2 and the total intensity of incident light I of the actual color conversion layer 0 The ratio of (A) to (B); eta is conversion efficiency, which represents the conversion efficiency of converting the quantum dots at the current position into the monochromatic light; beta is a normal number, called the absorption coefficient of the medium for the converted light.
Further, the calculating of the relationship between the converted monochromatic light intensity I and the change of the film thickness h and the quantum dot concentration c specifically includes:
let u be the product of the thickness h of the quantum dot light color conversion layer and the concentration c of the quantum dots, i.e. the actual amount of the quantum dots. The converted light has the following equilibrium formula:
i.e. the rate of change of the converted light is equal to the rate of change of the converted light resulting from the current position within the film minus the rate of change of the lost converted light;
in the formula (I), the compound is shown in the specification,
representing the rate of change of the generated converted light in the platelet material;
representing the rate of change of the loss of converted light by the platelet material;
setting the proportionality coefficient as eta; so I in Can be expressed as:
I in (u)＝kηI 0 ×10 -εu
where k is a proportionality coefficient representing the intensity of incident light into the channel 2 and the total intensity of incident light I from the actual color conversion layer 0 A ratio of; eta is conversion efficiency which represents the conversion efficiency of converting the quantum dots at the current position into the monochromatic light;
the loss equation of the converted monochromatic light is consistent with that of the incident light, and only the absorption coefficient epsilon' is changed, so that:
I out (u)＝I in ×10 -ε′u
will I in (u) and I out The above equation is substituted into the above equation, and since the actual amount u of quantum dots is 0, the converted light is not excited, the boundary conditions are:
I(0)＝0
the solution to this equation is then:
I(u)＝kηI 0 ×[10 -εu -10 -(ε+ε′)u ]
namely, the relationship of the converted monochromatic light intensity I along with the actual dosage u of the quantum dot, and the relationship that the converted monochromatic light intensity I changes along with the film thickness h and the concentration c of the quantum dot is obtained by substituting u = hc as follows:
I(h，c)＝kηI 0 ×[10 -εhc -10 -(ε+ε′)hc ]
where ε' is the molar absorption coefficient of the material of the converted monochromatic light, which is related to the material properties of the film and the wavelength λ of the converted light.
Further, once the actual amount u of the quantum dots of the quantum dot light-color conversion layer is determined, according to the relationship that u = hc, the preparation of the quantum dot color conversion layer can be actually guided by adjusting the film thickness h and the quantum dot concentration c, specifically:
fixing the film thickness h, and adjusting the quantum dot concentration c to realize a u value; fixing the concentration c of the quantum dots, and adjusting the film thickness h to realize a u value; and simultaneously adjusting the film thickness h and the quantum dot concentration c to realize the value u. Further, the quantum dot light color conversion layer has the maximum light conversion efficiency LCE max 。
The product of the quantum dot photochromic conversion layer thickness h and the quantum dot concentration c, namely the actual dosage u of the quantum dot, satisfies the expression:
in the formula u 0 Is a positive constant. The light conversion efficiency LCE of the quantum dot light color conversion layer is defined as the ratio of the emergent light intensity of the converted monochromatic light to the excitation light intensity of the light source entering the quantum dot light color conversion layer initially. The ratio has a maximum value and satisfies the following expression:
in the formula, LCE max Represents the maximum light conversion efficiency of the quantum dot light-color conversion layer.
Compared with the prior art, the invention has the following beneficial effects:
the invention can accurately and efficiently obtain the light-emitting optical performance parameters of the quantum dot light-color conversion layer, such as the light-emitting intensity and the light conversion efficiency of the converted light, and obtain the concentration of the quantum dots or the thickness parameter of the light-color conversion layer when the conversion efficiency of the converted light is maximum.
Drawings
Fig. 1 is a schematic light intensity block diagram of a logic channel division and a color conversion logic channel of a monochromatic sub-pixel region in a quantum dot light-color conversion layer designed in the embodiment of the present invention;
FIG. 2 is a flow chart of a design method of the thickness of the quantum dot light-color conversion layer and the concentration parameter of the quantum dot according to the present invention;
fig. 3 is an exemplary diagram of monochromatic light after the incident light is converted by the quantum dot light-color conversion layer according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of a blue Lambertian area light source with red/green quantum dot light conversion layer structures respectively deactivated;
fig. 5 is an exemplary diagram illustrating a structure of a light conversion layer of a red/green/blue quantum dot respectively deactivated in the ultraviolet lambertian area light source designed by the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
Referring to fig. 1, the present invention provides a method for calculating light conversion efficiency of a single-color quantum dot color conversion layer for display, comprising the following steps:
s1, acquiring initial parameters of a quantum dot light-color conversion layer;
s2, dividing logic channels of the color conversion layer according to different wavelengths or frequencies of light;
s3, constructing a theoretical relation model among monochromatic light converted by the quantum dot light-color conversion layer, the thickness of the diaphragm and the concentration of the quantum dots based on the quantum dot color conversion logic channel;
and S4, acquiring the optimal parameters of the film thickness and the concentration of the quantum dot light color conversion layer according to the theoretical relationship model.
And S5, establishing a theoretical relation among the light conversion efficiency, the membrane thickness and the quantum dot concentration.
In the embodiment, an optical theoretical model suitable for the patternable monochromatic quantum dot light-color conversion layer is provided, only one monochromatic quantum dot is contained in the quantum dot light-color conversion layer of the model, and the concentration of the quantum dots in the quantum dot light-color conversion layer is uniformly distributed. Incident short-wavelength light enters the quantum dot light-color conversion layer, and when part of incident light is attenuated in the quantum dot light-color conversion layer, the other part of incident light can excite the quantum dots to perform energy down-conversion and excite monochromatic light with longer wavelength.
The optical theory analysis of the model is realized by a method of dividing a logic channel of a color conversion layer according to different light wavelengths or frequencies, and the color conversion layer mixed with quantum dots is decomposed into a pure incident light logic channel 1 and a quantum dot color conversion logic channel 2 from a logic layer. The present application is directed to the emergent light intensity and the light conversion efficiency of the converted light of the color conversion logic channel 2, which are also the actual emergent light intensity and the light conversion efficiency of the converted light of the quantum dot light-color conversion layer.
The light intensity of the emitted converted light can change along with the thickness of the quantum dot light color conversion layer and the concentration value of the quantum dots in the film. The following expression is satisfied:
I(h，c)＝kηI 0 ×[10 -εhc -10 -(ε+ε′)hc ]
in the formula, I and I 0 Respectively representing the light intensity of the converted monochromatic light and the initial incident light intensity of the Lambert surface light source; h. c represents the thickness of the film and the concentration of the quantum dots, respectively; epsilon and epsilon' respectively represent the molar absorptivity of incident light and the molar absorptivity of the converted monochromatic light, and are related to the material property of the film, the wavelength of the incident light and the wavelength of the converted monochromatic light; k is a proportionality coefficient representing the intensity of incident light into the channel 2 and the total intensity of incident light I of the actual color conversion layer 0 The ratio of (A) to (B); η is conversion efficiency, which represents the conversion efficiency of the quantum dots at the current position to convert incident light into monochromatic light.
The light conversion efficiency LCE of the quantum dot light color conversion layer is the ratio of the light intensity of the converted monochromatic light to the initial incident light intensity of the light source. The following expression is satisfied:
in the formula, LCE represents the light conversion efficiency of the quantum dot light-color conversion layer.
Preferably, the model is suitable for the analysis of the converted light intensity and light conversion efficiency of a sub-pixel color conversion layer in a patternable quantum dot display device having a red/green/blue three primary color sub-pixel microstructure.
a: the light intensity of the red sub-pixel meets the following expression:
in the formula I r Representing the intensity of the converted red monochromatic light; epsilon b 、ε r Respectively, the molar absorptivity of the material for incident blue light and the molar absorptivity of the material for converted red monochromatic light, which are related to the material properties of the film and the wavelengths of the incident blue light and the converted red light. k is a radical of r Is a proportionality coefficient representing the intensity of blue light incident into the red sub-pixel region channel 2 for exciting red quantum dots and the total incident blue light intensity I 0 The ratio of (A) to (B); eta r For conversion efficiency, the conversion efficiency of converting blue light into red light by the red quantum dots at the current position is shown.
b: the light intensity of the green sub-pixel meets the following expression:
in the formula I g Representing the intensity of the converted green monochromatic light; epsilon g Which represents the molar absorption coefficient of the material after conversion for green monochromatic light, is related to the material properties of the film and the wavelength lambda of the converted green light. k is a radical of g Is a scale factor indicating that blue light is incident on the green sub-pixelBlue light intensity for exciting green quantum dots in area channel 2 and total incident blue light intensity I 0 The ratio of (A) to (B); eta g For conversion efficiency, the green quantum dots representing the current position convert the blue light to generate green light.
c: blue sub-pixel region: when the incident excitation light is blue light, quantum dots are not needed in the blue sub-pixels, and the color conversion process of the quantum dots does not exist, so that the conversion condition of the light can not be analyzed; when the incident excitation light is excitation light shorter than the blue wavelength, an appropriate amount of blue quantum dots needs to be added to the blue sub-pixel region, and the converted blue light has a luminous intensity similar to the aforementioned expressions for red and green.
The results are also applicable to the analysis of monochromatic quantum dot color conversion devices with similarly patternable structures. Such as micro-LEDs, QD-OLEDs, etc.
Preferably, the wavelength λ of the light source spectrum belongs to the short wavelength band, the wavelength range being between 10nm and 480 nm.
Preferably, the distance between the light emitting surface of the lambertian surface light source (including lambertian bodies such as a parallel surface light source) and the bottom surface of the quantum dot light color conversion layer is small, so that the light emitting surface can be considered to be closely attached to the quantum dot light color conversion layer and can not be too far away.
Preferably, the light emission width of the lambertian surface light source is equivalent to the length of the quantum dot light-color conversion layer, that is, if the width significantly exceeds the length of the quantum dot light-color conversion layer, the light emission width cannot be adapted to the demand.
Preferably, the quantum dot light-color conversion layer material is Propylene Glycol Monomethyl Ether Acetate (PGMEA) or the refractive index of the material is greater than the refractive index of air (approximately equal to 1).
In this embodiment, referring to fig. 2, a theoretical relationship model between monochromatic light converted by the quantum dot light-color conversion layer and the thickness and the concentration of the film is constructed, which specifically includes the following steps:
the first step is as follows: and determining initial parameters of the quantum dot light color conversion layer. The method comprises the following steps of using monochromatic quantum dot light-emitting spectral parameters, quantum dot color conversion layer film thickness and quantum dot concentration parameters, molar absorption coefficients of basic medium materials forming the color conversion layer respectively relative to incident light and converted light, and light intensity parameters of a Lambert surface light source.
The second step is that: and calculating the relation that the light intensity I' of the incident light changes along with the film thickness h. According to the Buerg-Lambert law: when the concentration of quantum dots in the photochromic conversion layer is fixed, the light intensity after the light passes through a certain medium is as follows:
I′(h)＝I 0 e -αh
in the formula I 0 The initial incident light intensity of the Lambert surface light source; h is the thickness of the quantum dot light-color conversion layer; α is a normal constant, called the absorption coefficient of the medium for the incident light. The dimension of the absorption coefficient α of the medium is the reciprocal of the length in cm -1 . The physical meaning of the reciprocal (1/alpha) of the absorption coefficient alpha is the thickness of the medium through which the light passes when the light intensity is attenuated to 1/e ≈ 36.8% due to the absorption of the medium.
The third step: and calculating the relation of the incident light intensity I' changing with the film thickness h and the quantum dot concentration c. According to lambert-beer's law:
A＝lg(1/T)＝εhc
wherein A is absorbance. T is the transmittance (transmittance), I' is the intensity of the emergent light and I is the intensity of the incident light 0 The ratio of (a) to (b). ε is the molar absorption coefficient of the material for the incident light, which is related to the material properties of the film and the wavelength λ of the incident light source. c is the concentration of the light-absorbing substance in mol/L, and h is the thickness of the absorbing layer in cm. Let T = I'/I 0 Substituting the equation to obtain:
I′(h，c)＝I 0 ×10 -εhc
namely a relational expression of the incident light intensity I' changing with the film thickness h and the quantum dot concentration c.
The fourth step: and calculating the relation of the light intensity I of the converted monochromatic light along with the change of the film thickness h and the concentration c of the quantum dots. Let u be the product of the thickness h of the quantum dot light color conversion layer and the concentration c of the quantum dots, i.e. the actual amount of the quantum dots. For the converted monochromatic light intensity, it is necessary to consider the generation and loss of the converted light during transmission, so that the following equilibrium formula exists for the converted light:
i.e. the rate of change of the converted light equals the rate of change of converted light resulting from the current position within the film minus the rate of change of converted light lost. In the formula (I), the compound is shown in the specification,
representing the rate of change of the generated converted light in the platelet material;
representing the rate of change of the loss of converted light by the platelet material.
Because the generation of the conversion light at the current position in the film depends on the incident light at the position, and the direct ratio of the conversion light and the incident light can be verified through a large number of experiments, the conversion efficiency is set as eta; so that I in Can be expressed as:
I in (u)＝kηI 0 ×10 -εu
where k is a proportionality coefficient representing the intensity of incident light into the channel 2 and the total intensity of incident light I of the actual color conversion layer 0 A ratio of; η is conversion efficiency, which indicates the conversion efficiency of the quantum dots at the current position to convert incident light into monochromatic light.
The loss mechanism of the converted monochromatic light is considered to be the same as that of the incident light, the loss equation of the converted monochromatic light is consistent with that of the incident light, and only the extinction coefficient epsilon' is changed, so that:
I out (u)＝I in ×10 -ε′u
will I in (u) and I out The above equation is substituted into the above equation, and since the actual amount u of quantum dots is 0, the converted light is not excited, the boundary conditions are:
I(0)＝0
the solution to this equation is then:
I(u)＝kηI 0 ×[10 -εu -10 -(ε+ε′)u ]
namely the relation of the converted monochromatic light intensity I along with the actual dosage u of the quantum dot, and the relation of the converted monochromatic light intensity I along with the change of the film thickness h and the concentration c of the quantum dot is obtained by substituting u = hc as follows:
I(h，c)＝kηI 0 ×[10 -εhc -10 -(ε+ε′)hc ]
where ε' is the molar absorption coefficient of the material of the converted monochromatic light, which is related to the material properties of the film and the wavelength λ of the converted light.
The fifth step: and (3) realizing the actual quantum dot dosage u of the quantum dot light-color conversion layer:
once the actual amount u of the quantum dots is determined, according to the relationship of u = hc, the preparation of the quantum dot color conversion layer can be actually guided by respectively adjusting the film thickness h and the quantum dot concentration c, specifically:
fixing the film thickness h, and adjusting the concentration c of the quantum dots to realize a u value; fixing the concentration c of the quantum dots, and adjusting the film thickness h to realize a u value; and simultaneously adjusting the film thickness h and the quantum dot concentration c to realize the u value.
And a sixth step: the relation that the converted monochromatic light intensity I changes along with the product of the thickness h of the quantum dot light-color conversion layer and the concentration c of the quantum dots, namely the actual dosage u of the quantum dots is as follows:
I(u)＝kηI 0 ×[10 -εu -10 -(ε+ε′)u ]
according to mathematical analysis, the converted monochromatic light has an extreme value, and the converted light is monotonically increased and then monotonically decreased, and has a maximum value. Namely:
taking a maximum value of the conversion efficiency, the maximum value satisfying the following expression:
in the formula, LCE represents the light conversion efficiency of the quantum dot light-color conversion layer, i.e. the ratio of the light intensity of the converted monochromatic light to the initial incident light intensity of the lambertian area light source. Thus according to epsilon, epsilon', i.e. material relating to incident lightCalculating the concentration c of the quantum dots when the conversion efficiency of the monochromatic light after conversion is maximum according to the molar absorption coefficient and the molar absorption coefficient of the material related to the monochromatic light after conversion and the thickness h of the light color conversion layer of the quantum dots; and calculating the thickness h of the quantum dot light-color conversion layer when the converted monochromatic light conversion efficiency is maximum according to the concentration c of the quantum dots. The physical significance is as follows: when the incident light intensity I 0 While the increase in the film thickness h and the quantum dot concentration c increases the conversion efficiency of the converted monochromatic light, the converted light also suffers from loss, but the product of the film thickness h and the quantum dot concentration c, i.e., the actual amount of quantum dots used, is less than u 0 When the light is converted, the conversion of the converted light is larger than the loss, so the light conversion efficiency gradually increases. But due to the intensity of incident light I 0 So that the conversion has a maximum value, i.e. when the product of the film thickness h and the quantum dot concentration c, i.e. the actual quantum dot dosage, is u 0 When the conversion is equal to the loss, the light conversion efficiency is maximized. If the film thickness h and the quantum dot concentration c are increased further, the conversion is less than the loss, and the light conversion efficiency is decreased.
The above description is only a preferred embodiment of the present invention, and all the equivalent changes and modifications made according to the claims of the present invention should be covered by the present invention.
Claims (5)
1. A method for calculating the light conversion efficiency of a single-color quantum dot color conversion layer for display is characterized by comprising the following steps of:
s1, acquiring initial parameters of a quantum dot color conversion layer;
s2, dividing logic channels of the quantum dot color conversion layer according to different light wavelengths or frequencies;
s3, constructing a theoretical relation model among monochromatic light converted by the quantum dot color conversion layer, the thickness of the diaphragm and the concentration of the quantum dots based on the quantum dot color conversion logic channel;
s4, acquiring the optimal parameters of the film thickness and the concentration of the quantum dot color conversion layer according to a theoretical relation model;
s5, establishing a theoretical relation among the light conversion efficiency, the thickness of the membrane and the concentration of the quantum dots;
the theoretical relationship model comprises:
when the concentration of the quantum dots is uniform and fixed, the relation that the light intensity of red/green monochromatic light generated after the quantum dots are excited by incident light changes along with the thickness of the film is obtained;
when the concentration of the quantum dots is uniform and the thickness of the color conversion layer of the quantum dots is fixed, the relation that the light intensity of red/green monochromatic light generated after the quantum dots are excited by incident light changes along with the concentration of the quantum dots is obtained;
when the concentration of the quantum dots is uniform and is variable, deducing the relation that the light intensity of the converted red/green monochromatic light changes along with the two variables of the film thickness and the concentration;
the converted monochromatic light intensity is obtained according to the relation of the film thickness and concentration change, and the relation is as follows: sequentially calculating the relation of the incident light intensity I' changing along with the film thickness h and the quantum dot concentration c according to the determined initial parameters of the quantum dot color conversion layer; the relationship that the converted monochromatic light intensity I changes along with the film thickness h, and the relationship that the converted monochromatic light intensity I changes along with the film thickness h and the quantum dot concentration c;
the calculation of the relationship between the incident light intensity I' and the change of the film thickness h and the concentration c is specifically as follows:
when the concentration of quantum dots in the quantum dot color conversion layer is fixed: according to the Booth-Lambert law, the light intensity after passing through a certain medium is:
I′(h)＝I 0 e -αh
in the formula I 0 The initial incident light intensity of the Lambert surface light source; h is the thickness of the quantum dot color conversion layer; alpha is a normal number and is the absorption coefficient of the medium to the incident light;
when the thickness in the quantum dot color conversion layer is fixed and the concentration of the quantum dots is uniformly changed: according to the Booth-Lambert law, the light intensity after passing through a preset medium is as follows:
I′(c)＝I 0 e -αc
wherein c is the concentration of quantum dots in the quantum dot color conversion layer;
the method comprises the following steps of calculating the relation that the incident light intensity I' changes along with the film thickness h and the quantum dot concentration c bivariate, specifically, according to the Lambert-beer law:
A＝lg(1/T)＝εhc
wherein A is absorbance, T is transmittance, and is emergent light intensity I' and incident light intensity I 0 The value of (a) is given as the material molar absorptivity with respect to the incident light, c is the concentration of the light-absorbing substance in mol/L, and h is the thickness of the absorbing layer in cm;
let T = I'/I 0 Substituting the equation to obtain:
I′(h,c)＝I 0 ×10 -εhc
namely a relational expression of the incident light intensity I' changing with the film thickness h and the quantum dot concentration c;
calculating the relation of the converted monochromatic light intensity I along with the change of the film thickness h and the quantum dot concentration c, and specifically:
making the product of the thickness h of the quantum dot color conversion layer and the concentration c of the quantum dots, namely the actual dosage of the quantum dots, be u; the converted light has the following equilibrium formula:
i.e. the rate of change of the converted light equals the rate of change of converted light resulting from the current position within the film minus the rate of change of converted light lost;
in the formula (I), the compound is shown in the specification,
representing the rate of change of the generated converted light in the platelet material;
representing the rate of change of the loss of converted light by the platelet material;
setting the conversion efficiency as eta; so that I in Can be expressed as:
I in (u)＝kηI 0 ×10 -εu
where k is a proportionality coefficient representing the total of the intensity of incident light into the channel 2 and the actual quantum dot color conversion layerIntensity of incident light I 0 The ratio of (A) to (B); eta is conversion efficiency, which represents the conversion efficiency of converting the quantum dots at the current position into the monochromatic light;
the loss equation of the converted monochromatic light is consistent with that of the incident light, and only the absorption coefficient epsilon' of the light with the corresponding wavelength is changed, then:
I out (u)＝I in ×10 -ε’u
will I in (u) and I out The above-mentioned balance formula is substituted into the relational expression of (u), and since the generation of converted light is not excited when the actual amount of quantum dots u is 0, the boundary conditions are:
I(0)＝0
the solution of this equation is then:
I(u)＝kηI 0 ×[10 -εu -10 -(ε+ε’)u ]
the relation of the converted monochromatic light intensity I along with the actual dosage u of the quantum dots is shown as follows, and the relation of the converted monochromatic light intensity I along with the change of the film thickness h and the concentration c of the quantum dots is obtained by substituting u = hc:
I(h,C)＝kηI 0 ×[10 -εhc -10 -(ε+ε′)hc ]
where ε' is the molar absorption coefficient of the material of the converted monochromatic light, which is related to the material properties of the film and the wavelength λ of the converted light.
2. The display-oriented calculation method for light conversion efficiency of a monochromatic quantum dot color conversion layer according to claim 1, wherein the initial parameters comprise monochromatic quantum dot light emission spectrum parameters, quantum dot color conversion layer film thickness and quantum dot concentration parameters, molar absorption coefficients of a base medium material forming the quantum dot color conversion layer with respect to incident light and converted light, respectively, and light intensity parameters of a lambertian area light source.
3. The method for calculating light conversion efficiency of a single-color quantum dot color conversion layer facing a display according to claim 1, wherein the logic channel is divided into: the quantum dot color conversion layer mixed with the monochromatic quantum dots is decomposed into a pure incident light logic channel 1 and a quantum dot color conversion logic channel 2 from a logic level.
4. The method of claim 1, wherein the method comprises the steps of: once the actual amount u of the quantum dots is determined, according to the relationship of u = hc, the preparation of the quantum dot color conversion layer can be actually guided by adjusting the film thickness h and the quantum dot concentration c, specifically:
fixing the film thickness h, and adjusting the concentration c of the quantum dots to realize a u value; fixing the concentration c of the quantum dots, and adjusting the film thickness h to realize a u value; and simultaneously adjusting the film thickness h and the quantum dot concentration c to realize the value u.
5. The method of claim 1, wherein the quantum dot color conversion layer has a maximum light conversion efficiency LCE max (ii) a When the product of the thickness h of the quantum dot color conversion layer and the concentration c of the quantum dots, namely the actual dosage u of the quantum dots, meets the expression:
in the formula u 0 Is a positive constant; the light conversion efficiency LCE of the quantum dot color conversion layer is defined as the ratio of the emergent light intensity of the converted monochromatic light to the excitation light intensity of the light source entering the quantum dot color conversion layer at the initial incidence; the ratio has a maximum value and satisfies the following expression:
in the formula, LCE max Representing the maximum light conversion efficiency of the quantum dot color conversion layer.
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