CN112414981A - Method for identifying single quantum dot photoluminescence scintillation mechanism - Google Patents
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/645—Specially adapted constructive features of fluorimeters
- G01N21/6456—Spatial resolved fluorescence measurements; Imaging
- G01N21/6458—Fluorescence microscopy
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6489—Photoluminescence of semiconductors
Abstract
The invention discloses a method for identifying a single quantum dot photoluminescence scintillation mechanism, which comprises the steps of exciting a single quantum dot by using a pulse laser, and carrying out time-marked single photon counting on photoluminescence photons of the single quantum dot by using a time-resolved single photon counting system; and finally determining the photoluminescence scintillation mechanism of the quantum dots by utilizing the photoluminescence intensity track curve, the photoluminescence attenuation curve, the single exponential function fitting curve and the photoluminescence intensity-radiance distribution diagram of the single quantum dots. The method can help effectively inhibit the photoluminescence flicker of the perovskite quantum dots by adopting a corresponding strategy through effectively identifying the photoluminescence flicker mechanism of the perovskite quantum dots, thereby effectively improving the luminous efficiency and the light stability of the perovskite quantum dots. The effective identification of the perovskite quantum dot photoluminescence scintillation mechanism has very important significance for preparing high-quality perovskite quantum dots and related applications thereof.
Description
Technical Field
The invention relates to the technical field of semiconductor luminescent materials, in particular to a method for identifying a single quantum dot photoluminescence scintillation mechanism.
Background
The halogenated perovskite quantum dot has the advantages of low manufacturing cost, easiness in processing, higher immunity to defects and surface capture due to photoelectric characteristics, and very high photoluminescence quantum yield. Can be widely applied to the preparation of devices such as light emitting diodes, solar cells, lasers, detectors, quantum light sources and the like, thereby receiving wide attention of people. However, the photoluminescence intensity at the perovskite single quantum dots can be randomly switched between the bright and dark states, i.e., photoluminescence scintillation. Photoluminescence scintillation has greatly limited the application of perovskite quantum dots to a variety of devices.
The perovskite quantum dots emit photoluminescence and flicker by two mechanisms, namely non-radiative Auger recombination and surface capture induced non-radiative recombination. The non-radiative auger recombination mechanism is photoluminescence scintillation due to the charging and discharging processes of the perovskite quantum dots. The ability to trigger non-radiative auger recombination can lead to quenching of photoluminescence when the quantum dots are charged. When the charged quantum dots are discharged and converted into neutral quantum dots, the photoluminescence intensity can be recovered. The surface capture induced photoluminescence scintillation mechanism is due to the fact that the surface capture of the quantum dots provides non-radiative recombination channels for excitons of the quantum dots, and therefore photoluminescence of the quantum dots is quenched. Due to the continuous change of the non-radiative recombination rate induced by the activation and deactivation of the surface capture state, the photoluminescence scintillation of the perovskite quantum dots is caused.
Therefore, the method for effectively identifying the photoluminescence scintillation mechanism of the perovskite quantum dots has important significance for inhibiting the photoluminescence scintillation by utilizing corresponding means.
Disclosure of Invention
An objective of the present invention is to provide a method for identifying a single quantum dot photoluminescence scintillation mechanism, which can efficiently identify the single quantum dot photoluminescence scintillation mechanism.
The second objective of the present invention is to provide the application of the method for identifying a single quantum dot photoluminescence scintillation mechanism in the field of single quantum dot photoluminescence scintillation mechanism identification.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method of identifying a single quantum dot photoluminescence scintillation mechanism, comprising:
s1, exciting a single quantum dot by using a pulse laser, and carrying out photoluminescence imaging on the quantum dot;
s2, exciting a bright color area on the confocal photoluminescence imaging at a fixed point, and performing time-marked single photon counting on photoluminescence photons of the single quantum dots by using a time-resolved single photon counting system;
s3, obtaining a photoluminescence intensity track curve based on single photon counting data of the single quantum dots;
s4, segmenting the photoluminescence intensity track curve by time units, and extracting photoluminescence intensity and attenuation curves in each time unit; normalizing the photoluminescence intensity, and taking the quantum yield of the highest intensity value as 1 to obtain the average photoluminescence quantum yield in each time unit; performing single exponential fitting on the photoluminescence decay curve to obtain the photoluminescence life of the excitons;
s5, calculating the radiance (k) of the quantum dots in each time unit by using a formula (1) according to the average quantum yield (eta) and the photoluminescence life (tau) in each time unitr)；
kr＝η/τ (1)
S6, drawing a photoluminescence intensity-radiance distribution diagram by taking the radiance in each time unit as a function of the average photoluminescence intensity in the corresponding time unit;
and S7, determining a photoluminescence flicker mechanism of the quantum dots according to the distribution form of the data dots of the photoluminescence intensity-radiance distribution diagram.
The inventors of the present application found through research that the radiance distribution of the quantum dots is different due to the difference in the origin of the photoluminescence scintillation mechanism causing the single quantum dots, and thus, the photoluminescence scintillation mechanism of the quantum dots can be effectively identified from the radiance distribution form of the single quantum dots.
In some preferred embodiments of the invention, the quantum dots are perovskite single quantum dots.
In some preferred embodiments of the present invention, in step S1, the quantum dots are perovskite single quantum dots, and the laser wavelength emitted by the pulse laser is 450 nm.
In some preferred embodiments of the present invention, in step S4, every 30ms is a time unit.
In some preferred embodiments of the present invention, in step S7, in the photoluminescence intensity-radiance distribution map, the distribution form of the data points is a horizontal linear distribution, indicating that the photoluminescence scintillation mechanism of such perovskite single quantum dots is surface capture-induced photoluminescence scintillation; the distribution form of the data points is exponential distribution, and the photoluminescence scintillation mechanism of the perovskite single quantum point is the photoluminescence scintillation induced by Auger recombination, so that the perovskite single quantum point photoluminescence scintillation mechanism is effectively identified.
In order to achieve the second purpose, the invention adopts the following technical scheme:
the method for identifying the single quantum dot photoluminescence scintillation mechanism is applied to the field of identification of the single quantum dot photoluminescence scintillation mechanism.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
in the embodiment of the invention, by effectively identifying the photoluminescence scintillation mechanism of the perovskite quantum dots, the corresponding strategy can be helped to effectively inhibit the photoluminescence scintillation of the perovskite quantum dots, so that the luminous efficiency and the light stability of the perovskite quantum dots are effectively improved. The effective identification of the perovskite quantum dot photoluminescence scintillation mechanism is of great significance for preparing high-quality perovskite quantum dots and related applications thereof.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a photo-luminescence image of a perovskite single quantum dot provided in example 1 of the present invention;
fig. 2 is a photoluminescence intensity trace curve of a perovskite single quantum dot provided in embodiment 1 of the present invention, wherein the fluctuation and fluctuation of the intensity trace curve are photoluminescence flicker of the quantum dot;
FIG. 3 is a photoluminescence decay curve and a single exponential function fitting curve of perovskite single quantum dots provided in example 1 of the present invention, wherein a dotted line is an instrument response function of the system;
FIG. 4 is a graph of photoluminescence intensity-radiance distribution of perovskite single quantum dots provided in example 1 of the present invention, wherein a horizontal line-type distribution indicates that the photoluminescence scintillation of the quantum dots is surface capture induced photoluminescence scintillation;
FIG. 5 is a plot of photoluminescence intensity traces of perovskite single quantum dots provided in example 2 of the present invention;
fig. 6 is a photoluminescence intensity-radiance distribution diagram of a perovskite single quantum dot provided in example 2 of the present invention, wherein an index distribution indicates that the photoluminescence scintillation of the quantum dot is auger recombination-induced photoluminescence scintillation;
fig. 7 is a flow chart of the identification of the perovskite single quantum dot photoluminescence scintillation mechanism provided in examples 1-2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available from commercial sources.
In the following embodiments, each performance index testing apparatus is as follows:
1. the confocal scanning imaging system comprises the following components:
the excitation light source was a picosecond supercontinuum laser (EXW-12, NKT, 50-100ps), wavelength 450nm, pulse repetition rate 10 MHz. The laser passes through a lambda/2 slide, a lambda/4 slide, and a laser beam expander. An inverted fluorescence microscope (Olympus, IX71) is arranged on the exit light path of the laser beam expander. An incident port of the inverted fluorescence microscope is located on an emergent light path of the laser beam expander, and the expanded laser is filtered by an excitation filter (Semrock) and then reflected by a dichroic mirror (Semrock) to enter a microscope objective lens (Olympus, 100 × oil, NA ═ 1.3).
The front end of the microscope objective is provided with a three-dimensional nanometer displacement table (Tritor 200/20SG) for carrying a sample, and a notch filter (Semrock), an emission filter (Semrock) and a confocal pinhole with the aperture of 100 mu m are sequentially arranged on a fluorescence collection light path of the inverted fluorescence microscope. The fluorescent photons passing through the confocal pinhole are converged by a focusing lens and photon detected by a single photon detector (SPCM-AQR-15, PerkinElmer). And enabling the TTL signal output by the single-photon detector to enter a time correlation single-photon counting system for time-stamped single-photon counting measurement.
2. The measurement of the test sample is carried out by means of various known instruments, in particular those which comprise:
fluorescence inverted microscope (Olympus, IX 71);
picosecond supercontinuum lasers (EXW-12, NKT, 50-100 ps);
a three-dimensional nano-platform (Tritor 200/20 SG);
single photon detectors (SPCM-AQR-15, Perkinelmer);
time-correlated single photon counting acquisition card (HydraHarp 400)
3. The software programs included self-compiled LabVIEW and MATLAB data acquisition and analysis programs.
Example 1
The specific flow of the photoluminescence scintillation mechanism identification of the perovskite quantum dots is shown in fig. 7.
S1, preparing a perovskite single quantum dot sample
To a concentration of 10-9mol/L of CH3NH3PbBr3And (3) carrying out spin coating on the surface of a clean cover glass by using a toluene solution of the perovskite quantum dots, wherein the spin coating speed is 2000 rpm, and the spin coating time is 1 minute. 1 wt% polystyrene toluene solution is spin-coated on the perovskite quantum dots for protecting the perovskite quantum dots. CH as mentioned above3NH3PbBr3The central peak of the photoluminescence emission wavelength of the perovskite quantum dots is 512nm, and the quantum yield is about 82%. The perovskite quantum dot sample is placed on a nanometer displacement object stage of a confocal scanning imaging system and used for identifying a perovskite single quantum dot photoluminescence scintillation mechanism.
S2, collecting fluorescence photons of the perovskite single quantum dots by using the experimental device, exciting the single quantum dots on the nano-displacement object stage by using a 450nm picosecond supercontinuum pulse laser, and carrying out photoluminescence imaging on the quantum dots, wherein the photoluminescence imaging is shown in figure 1. The bright color spot in fig. 1 is the photoluminescence signal of a perovskite single quantum dot.
And S3, carrying out fixed-point excitation on the bright-color light spots in the graph 1, and carrying out time-marked single photon counting on photoluminescence photons of the quantum dots by using a time-dependent single photon counting system to obtain photoluminescence intensity tracks of the perovskite single quantum dots, wherein the fluctuation and fluctuation of an intensity track curve are photoluminescence flicker of the quantum dots as shown in the graph 2.
S4, intensity normalization is carried out on the intensity track curve of the graph 2, and the quantum yield of the highest intensity value (500counts/10ms) is taken as 1. And (3) dividing the photoluminescence intensity track curve by taking 30ms as a time unit, and extracting the average quantum yield of the photoluminescence intensity in each time unit and the corresponding photoluminescence attenuation curve. For example, a typical photoluminescence decay of one of the time units (the first 30ms from time 0 in fig. 2) extracted from fig. 2The curves are shown in figure 3. The photoluminescence decay curve can be fitted by a single exponential to obtain an exciton lifetime of 8.5ns, and the average quantum yield of the photoluminescence intensity of the time unit is 0.493. The exciton radiance of the time cell is 0.058X 10 according to the formula (1)-9ns。
And S5, calculating the exciton radiance of each time unit of the intensity track curve of the graph in the figure 2, and taking the exciton radiance as a function of the normalized photoluminescence intensity to obtain the photoluminescence intensity-radiance distribution graph of the perovskite single quantum dots shown in the figure 4. Since the surface trap state of the perovskite quantum dots does not cause a change in the exciton emission characteristics, the exciton emission of the perovskite quantum dots remains constant for different photoluminescence intensities. Thus, a horizontal linear profile of the photoluminescence intensity-radiance profile indicates that the photoluminescence scintillation of the quantum dot is a surface capture induced photoluminescence scintillation.
Example 2
The specific flow of the photoluminescence scintillation mechanism identification of the perovskite quantum dots is shown in fig. 7.
Example 2 the experimental procedure was essentially the same as example 1, except that:
perovskite quantum dots for experiments are purchased and bought from crystallography technology (Beijing) Co.
S6, FIG. 5 is a photoluminescence intensity trajectory curve of the perovskite single quantum dot, and the photoluminescence intensity-radiance distribution diagram of the perovskite single quantum dot shown in FIG. 6 can be obtained by calculating the exciton radiance of each time unit of the intensity trajectory curve. Since the photoluminescence scintillation of the perovskite quantum dot is caused by auger recombination caused by charging inside the quantum dot, the charge inside the charged quantum dot can cause the exciton radiance to change, and the ratio of the maximum radiance to the minimum radiance is 2, the exciton radiance of the perovskite quantum dot is different for different photoluminescence intensities. Thus, an exponential distribution of the photoluminescence intensity-radiance profile indicates that the photoluminescence scintillation of the quantum dot is auger recombination-induced photoluminescence scintillation.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A method of identifying a single quantum dot photoluminescence scintillation mechanism, comprising:
s1, exciting a single quantum dot by using a pulse laser, and carrying out photoluminescence imaging on the quantum dot;
s2, exciting a bright color area on the confocal photoluminescence imaging at a fixed point, and performing time-marked single photon counting on photoluminescence photons of the single quantum dots by using a time-resolved single photon counting system;
s3, obtaining a photoluminescence intensity track curve based on single photon counting data of the single quantum dots;
s4, segmenting the photoluminescence intensity track curve by time units, and extracting photoluminescence intensity and attenuation curves in each time unit; normalizing the photoluminescence intensity, and taking the quantum yield of the highest intensity value as 1 to obtain the average photoluminescence quantum yield in each time unit; performing single exponential fitting on the photoluminescence decay curve to obtain the photoluminescence life of the excitons;
s5, calculating the radiance of the quantum dots in each time unit according to the average quantum yield and the photoluminescence service life in each time unit;
s6, drawing a photoluminescence intensity-radiance distribution diagram by taking the radiance in each time unit as a function of the average photoluminescence intensity in the corresponding time unit;
and S7, determining a photoluminescence flicker mechanism of the quantum dots according to the distribution form of the data dots of the photoluminescence intensity-radiance distribution diagram.
2. The method according to claim 1, wherein in step S1, the quantum dots are perovskite single quantum dots.
3. The method according to claim 2, wherein in step S1, the quantum dots are perovskite single quantum dots; the laser wavelength emitted by the pulse laser is 450 nm.
4. The method of claim 3, wherein the: in step S4, each 30ms is used as a time unit.
5. The method as claimed in claim 3, wherein in step S7, the distribution of data points in the photoluminescence intensity-radiance distribution graph is in the form of horizontal linear distribution, and the photoluminescence scintillation mechanism of the perovskite single quantum dots is surface capture induced photoluminescence scintillation; the distribution form of the data points is exponential distribution, and the photoluminescence scintillation mechanism of the perovskite single quantum points is Auger recombination-induced photoluminescence scintillation.
6. The method of claim 1 applied to the field of single quantum dot photoluminescence scintillation mechanism identification.
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| US20140021371A1 (en) * | 2012-07-23 | 2014-01-23 | Paul R. Selvin | Two-photon 3-d fiona of individual quantum dots |
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| CN104020148A (en) * | 2009-07-20 | 2014-09-03 | Bt成像股份有限公司 | Separation of doping density and minority carrier lifetime in photoluminescence measurement |
| US20140021371A1 (en) * | 2012-07-23 | 2014-01-23 | Paul R. Selvin | Two-photon 3-d fiona of individual quantum dots |
| CN111218283A (en) * | 2018-11-23 | 2020-06-02 | 中国科学院大连化学物理研究所 | Alloy quantum dot capable of remarkably inhibiting Auger recombination and preparation and application thereof |
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