CN108305948B - A method for controlling the structure of multiple quantum wells in perovskite materials and its applications and devices - Google Patents

Abstract

The invention discloses a multi-quantum well structure regulation method of perovskite material based on thin film post-processing, application and device thereof. The multi-quantum well structure of perovskite material is regulated by the thin-film post-processing process; the material selected is self-assembly. A perovskite material forming a multiple quantum well structure, the material is prepared from AX ¹ , BX ² and MX ³ ₂ in a molar ratio a:b:c, wherein A is R ^1- Y ⁺ , and R ^1- is a Aliphatic hydrocarbon groups of 50 carbon atoms, alicyclic hydrocarbon groups of 5 to 100 carbon atoms, optionally substituted aryl groups of 6 to 100 carbon atoms, or optionally substituted heterocyclic groups of 3 to 100 carbon atoms , Y ⁺ is any one of amine, N-containing heterocyclic organic cation; B is methylamine, formamidine or metal ion; M is metal element; X ¹ X ² X ³ is halogen element; : One or a combination of thermal annealing, solvent annealing, and vacuum drying; the device efficiency can be optimized through the regulation of the multiple quantum well structure.

Description

A method for controlling the structure of multiple quantum wells in perovskite materials and its applications and devices

technical field

The organic-inorganic hybrid perovskite material, in particular, relates to a method for controlling the structure of multiple quantum wells of perovskite material based on thin film post-processing, and its application and device.

Background technique

In recent years, organic-inorganic hybrid perovskite materials have become "stars" in the field of solar cells, and device performance has achieved rapid development. At present, the energy conversion efficiency of photovoltaic devices has exceeded 22%. In addition to the field of photovoltaics, perovskite materials have also attracted widespread attention in the field of luminescence. However, the current device efficiency and stability are low, and new materials and new structures need to be used to improve device performance.

Recently, perovskite light-emitting devices with multiple quantum well structures have shown the advantages of high efficiency and stability (China Patent Application No.: 201610051400.4). However, in the current preparation process of perovskite devices with multiple quantum well structures, there is no simple, An efficient method for tuning quantum well structures. Although the method of regulating quantum well structure in traditional inorganic luminescence can be used for reference, the preparation conditions of inorganic quantum wells are harsh and the cost is high, which is not conducive to low-cost and large-area device preparation. Therefore, it is necessary to further propose a method to optimize the quantum well structure to improve the performance of perovskite devices.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for controlling the structure of multiple quantum wells of perovskite material based on thin film post-processing, and its application and device.

The technical scheme of the present invention is as follows:

A method for regulating the multi-quantum well structure of perovskite materials based on thin-film post-processing. The multi-quantum well structure of perovskite materials is adjusted through a thin-film post-processing process; the selected material is a perovskite that can self-assemble to form a multi-quantum well structure. material, the material is prepared from AX ¹ , BX ² and MX ³ ₂ in molar ratio a:b:c, wherein A is R ^1- Y ⁺ , R ^1- is an aliphatic hydrocarbon group with 1 to 50 carbon atoms, Alicyclic hydrocarbon group with 5-100 carbon atoms, optionally substituted aryl group with 6-100 carbon atoms or optionally substituted heterocyclic group with 3-100 carbon atoms, Y ⁺ is amine, N-containing heterocyclic group Any one of the cyclic organic cations; B is methylamine, formamidine or metal ion; M is a metal element; X ¹ X ² X ³ is a halogen element; film post-treatment conditions are: heating annealing, solvent annealing, vacuum drying One of the three or their combination; the optimization of the device efficiency can be achieved through the control of the multiple quantum well structure.

In the method for regulating and controlling the structure of multiple quantum wells, the heating and annealing conditions are as follows: the substrate spin-coated with the precursor solution is placed on a heating stage at a certain temperature for 0-5h.

In the method for regulating and controlling the structure of multiple quantum wells, the solvent annealing conditions are as follows: the substrate spin-coated with the precursor solution is placed in a container maintaining a solvent atmosphere for 0-24 hours.

In the method for regulating and controlling the structure of multiple quantum wells, the vacuum drying conditions are as follows: the substrate spin-coated with the precursor solution is placed in a vacuum chamber for 0-24 hours.

In the method for controlling the structure of multiple quantum wells, the representative materials AX ¹ used are C ₁₀ H ₇ CH ₂ NH ₃ I, C ₁₀ H ₇ CH ₂ NH ₃ Br, C ₆ H ₅ CH ₂ NH ₃ I, C _6H5 ( _{CH2 ) 2NH3I} , _{C6H5 ( CH2 ) 4NH3I} , _BX2 is _CH3NH3I , _{NH2CH = NH2I} , CsI, _{NH2CH = NH2} Br, NH ₂ CH=NH ₂ Cl, CH ₃ NH ₃ Br, CH ₃ NH ₃ Cl, CsBr, CsCl, MX ³ ₂ is PbI ₂ , PbBr ₂ , PbCl ₂ , including but not limited to.

In the application of any one of the control methods, the multi-quantum well structure of the perovskite material is adjusted through a thin film post-treatment process.

A device prepared according to any one of the control methods.

Aiming at the requirement for adjustment of the multi-quantum well structure of the perovskite thin film, the present invention proposes a simple post-processing method based on the thin film, which can realize the regulation of the multi-quantum well structure of the perovskite material and optimize the film-forming properties and optoelectronic properties of the perovskite thin film. , thereby improving the performance of perovskite light-emitting devices.

Description of drawings

Fig. 1 is the schematic diagram of the formation of multiple quantum well structure of perovskite material provided by the present invention;

Fig. 2 is the absorption spectrogram of the perovskite thin film of embodiment 1 provided by the present invention;

Fig. 3 is the photoluminescence spectrogram of the perovskite thin film of Example 1 provided by the present invention;

Fig. 4 is the absorption spectrum diagram of the perovskite thin film of embodiment 2 provided by the present invention;

Fig. 5 is the photoluminescence spectrogram of the perovskite thin film of Example 2 provided by the present invention;

Fig. 6 is the absorption spectrum diagram of the perovskite thin film of embodiment 3 provided by the present invention;

Fig. 7 is the photoluminescence spectrogram of the perovskite thin film of Example 3 provided by the present invention;

Fig. 8 is the absorption spectrum diagram of the perovskite thin film of embodiment 4 provided by the present invention;

9 is a photoluminescence spectrogram of the perovskite thin film of Example 4 provided by the present invention;

Fig. 10 is the X-ray diffraction spectrum of the perovskite film of Example 4 provided by the present invention;

11 is an AFM image of the perovskite thin film of Example 4 provided by the present invention;

12 is a schematic structural diagram of the perovskite device of Example 5 provided by the present invention;

13 is the electroluminescence spectrum of the MQW LED device of Example 5 provided by the present invention;

Fig. 14 is the relationship curve of voltage-current density-radiation intensity of the MQWLED device of Example 5 provided by the present invention;

15 is a current density-external quantum efficiency relationship curve of the MQW LED device of Example 5 provided by the present invention;

Detailed ways

The present invention will be described in detail below with reference to specific embodiments.

The technical scheme of the present invention provides a method for adjusting the multi-quantum well structure of perovskite material through a thin film post-treatment process. The selected material is a perovskite material that can self-assemble to form a multi-quantum well structure, which is prepared from AX ¹ , BX ² and MX ³ ₂ in a molar ratio a:b:c, wherein A is R ^1- Y ⁺ , R ^1- is an aliphatic hydrocarbon group having 1-50 carbon atoms, an alicyclic hydrocarbon group having 5-100 carbon atoms, an optionally substituted aryl group having 6-100 carbon atoms, or an aryl group having 3-100 carbon atoms optionally substituted heterocyclic group, Y ⁺ is any one of amine, N-containing heterocyclic organic cation; B is methylamine, formamidine or metal ion; M is a metal element; X ¹ X ² X ³ is a halogen group element; when X ¹ , X ² , and X ³ are uniformly represented by X, their structural formula can be represented as A ₂ B _{n- 1 Mn} X _3n+1 , where n is the number of layers of the inorganic framework of the perovskite material . _{Representative materials AX1 used are C10H7CH2NH3I ,} ^{C10H7CH2NH3Br} _{, C6H5CH2NH3I , C6H5 ( CH2 ) 2NH3 _ _} I, C ₆ H ₅ (CH ₂ ) ₄ NH ₃ I, BX ₂ is CH ₃ NH ₃ I, NH ₂ CH=NH ₂ I, CsI, NH ₂ CH=NH ₂ Br, NH ₂ CH=NH ₂ Cl, CH ₃ NH ₃ Br, CH ₃ NH ₃ Cl, CsBr, CsCl, MX ³ ₂ are PbI ₂ , PbBr ₂ , PbCl ₂ , including but not limited to. Film post-treatment conditions: heating annealing time is 0-5h, solvent annealing time is 0-24h, and vacuum drying time is 0-24h. As shown in Figure 1, the perovskite multiple quantum well structure can be regulated by post-processing. The optimization of the device efficiency can be achieved through the control of the multiple quantum well structure.

Example 1 Using the thermal annealing method to control the perovskite multiple quantum well structure on a quartz substrate.

C ₁₀ H ₇ CH ₂ NH ₃ I, NH ₂ CH=NH ₂ I (FAI) and PbI ₂ were prepared as a precursor solution (NFPI ₇ ) in a molar ratio of 2:1:2, which was spin-coated on a quartz substrate. The precursor solution was annealed at 100 °C on a heating table for 0 min, 5 min, 10 min, 20 min, 30 min, and 60 min, respectively. After annealing, perovskite films with different multiple quantum well structures were obtained.

As shown in Figure 2, the annealed NFPI ₇ film has an obvious exciton absorption peak at 567 nm, indicating that the quantum well structure has been formed at this time, and there are many n=2 quantum wells, which can also be seen from the figure There is also an absorption peak at 632nm, corresponding to the quantum well structure of n=3, and there is a certain absorption near 774nm, indicating that there is also a large n quantum well structure (narrow energy gap) in the material, and the large n quantum well structure exists The structure of three-dimensional perovskite materials has been approached. On the unannealed film (annealing time is 0 min), no obvious exciton absorption peak is seen, and there is no absorption of the three-dimensional perovskite material, indicating that the multi-quantum well perovskite structure has not yet formed in the unannealed material. . Figure 3 shows the photoluminescence spectrum of the NFPI ₇ thin film. It can be seen that as the annealing time increases from 5 min to 60 min, the main peak of the thin film luminescence red shifts from 743 nm to 772 nm, which is close to the luminescence peak of the three-dimensional FAPbI ₃ , corresponding to the large n quantum The luminescence of the well component indicates that in the layered perovskite material, the amount of the narrow-energy-gap quantum well component in the film increases continuously during the process of increasing the annealing time from 0 min to 60 min, that is, the narrow-energy gap quantum well width becomes wider. . In addition to the main luminescence peak, there are also luminescence peaks at 516nm, 577nm, 646nm and a shoulder peak at 688nm in the film, corresponding to the luminescence of the quantum well structures with n=1, 2, 3, and 4, respectively. Combined with the absorption spectrum, it can be found that changing the annealing time of the film can control the multi-quantum well structure in the film. transfer.

Example 2 Using a solvent annealing method to tune the perovskite multiple quantum well structure on a ZnO/PEIE substrate.

C ₁₀ H ₇ CH ₂ NH ₃ I, NH ₂ CH=NH ₂ I (FAI) and PbI ₂ were prepared as a precursor solution (NFPI ₇ ) in a molar ratio of 2:1:2, which was spin-coated on a quartz substrate. precursor solution. An airtight container with a volume of about 500 mL was selected, an open vial containing 100 μL of DMF solution was placed in the container, and the container was placed at a constant temperature of 50°C to keep the atmosphere of DMF in the container. The prepared samples were placed in an airtight container, placed in sequence for 0 h, 1 h, 2 h, 6 h, 12 h, and 24 h, and then taken out to obtain perovskite films with different multiple quantum well structures.

As shown in Figure 4, the NFPI ₇ film after solvent annealing treatment has an obvious exciton absorption peak at 567 nm, which corresponds to the n=2 quantum well structure, indicating that the quantum well structure has been formed at this time. It can also be seen from the figure that there is also an absorption peak at 632nm, corresponding to the quantum well structure of n=3, and there is a certain absorption near 805nm, indicating the existence of a large n quantum well structure (narrow energy gap) in the material, And the large-n quantum well structure is close to the structure of three-dimensional perovskite materials. Figure 5 shows the photoluminescence spectrum of the NFPI ₇ film. It can be seen that as the annealing time increases from 1h to 24h, the main peak of the film's luminescence red-shifts from 786nm to 792nm, corresponding to the luminescence of the large n quantum well component. In the layered perovskite material, in addition to the main luminescence peak, there are also luminescence peaks at 518 nm, 572 nm, 639 nm, and shoulder peaks at 684 nm, corresponding to n=1, 2, 3, and 4 quantum wells, respectively. The glow of the structure. The optical characterization results show that the perovskite film with quantum well structure can also be obtained by solvent annealing, and the function of regulating the multiple quantum well structure in the film can be achieved by changing the solvent treatment time of the film.

Example 3 Using the vacuum drying method to control the perovskite multiple quantum well structure on the quartz substrate.

C ₁₀ H ₇ CH ₂ NH ₃ I, NH ₂ CH=NH ₂ I (FAI) and PbI ₂ were prepared as a precursor solution (NFPI ₇ ) in a molar ratio of 2:1:2, which was spin-coated on a quartz substrate. precursor solution. Place the spin-coated sample in a vacuum chamber, evacuate the vacuum chamber to achieve a vacuum atmosphere of <10Pa, and take out the samples placed in the vacuum atmosphere for 0h, 1h, 2h, 5h, 10h, and 20h in turn. Perovskite films with different multiple quantum well structures were obtained.

As shown in Figure 6, the annealed NFPI ₇ film has an obvious exciton absorption peak at 570 nm, and there are many n=2 quantum wells. It can also be seen from the figure that there is also an absorption peak at 639 nm. Corresponds to the quantum well structure of n=3. Figure 7 is the photoluminescence spectrum of the NFPI ₇ thin film. It can be seen that as the annealing time increases from 1h to 20h, the main peak of the thin film luminescence red-shifts from 752nm to 780nm, which corresponds to the luminescence of the large n quantum well component, indicating that in In the layered perovskite material, during the process of increasing the annealing time to 20h, the amount of the narrow-energy-gap quantum well components in the film increases continuously, that is, the narrow-energy-gap quantum well width becomes wider. In addition to the main luminescence peaks, there are also luminescence peaks at 516nm, 576nm, 646nm and shoulder peaks at 688nm in the film, corresponding to the luminescence of the quantum well structures with n=1, 2, 3, and 4, respectively. The optical characterization results show that the perovskite film with multiple quantum well structure can also be obtained by vacuum drying, and the function of regulating the multiple quantum well structure in the film can be achieved by changing the drying time of the film.

Example 4 The perovskite multiple quantum well structure on the ZnO/PEIE substrate is regulated by the thermal annealing method.

Perovskite thin films were prepared on ZnO/PEIE substrates to study the morphology and luminescence properties of perovskite thin films. The specific preparation method is as follows:

①Using acetone solution, ethanol solution and deionized water to ultrasonically clean the transparent conductive substrate ITO glass, and dry it with dry nitrogen after cleaning;

② Move the dried substrate into a vacuum chamber, and pre-treat the ITO glass with ultraviolet and ozone for 10 minutes in an oxygen pressure environment;

③ Spin-coat ZnO and PEIE on the treated substrates, and anneal them, and then transfer them to a nitrogen glove box;

④ Spin-coat the precursor solution (NFPI ₇ ) with the molar ratio of C ₁₀ H ₇ CH ₂ NH ₃ I, NH ₂ CH=NH ₂ I (FAI) and PbI ₂ on ZnO/PEIE, 100 ℃ heating and annealing, annealing for 0min, 5min, 10min, 20min, 30min, 60min respectively, after annealing, perovskite films with different multiple quantum well structures were obtained.

Figure 8 shows the absorption spectra of films prepared from NFPI ₇ precursor solutions at different annealing times. As shown in the figure, the annealed NFPI ₇ film has an obvious exciton absorption peak at 567 nm, indicating the existence of a large number of n=2 quantum well structures in the material. As the annealing time increases, the exciton absorption peak of n=2 decreases gradually, which means that the quantum well structure composition of n=2 decreases. At the same time, it can be seen that there is obvious absorption near 785nm, and the absorption increases with the increase of annealing time, indicating the existence of large-n quantum wells in the material, and with the increase of annealing time, the composition of large-n increases. Figure 9 shows that the photoluminescence main peak of the film is located near 787nm, which is close to the luminescence of three-dimensional FAPbI _3. With the increase of annealing time, the luminescence main peak appears red-shifted from 778nm to 791nm, which is more and more close to the luminescence peak of FAPbI ₃ . In the quantum well perovskite material, with the progress of the annealing process, the amount of the narrow-bandgap quantum well components in the film is also increasing, and the width of the narrow-bandgap quantum well becomes wider. In addition, there are luminescence peaks at 516nm, 574nm, 635nm and a shoulder peak at 681nm in the film, corresponding to the perovskite luminescence with n=1, 2, 3, and 4 quantum well structures, respectively. The luminescence corresponding to the increase of annealing time n=2, 3, and 4 weakened, indicating that the quantum well composition of n=2, 3, and 4 in the film decreased. Combined with the absorption spectrum, it can be found that changing the annealing time of the film has a regulating effect on the multi-quantum well structure in the film. Trap transfer.

Figure 10 corresponds to the X-ray diffraction spectrum (XRD) of NFPI ₇ thin films at different annealing times. It can be found that with the increase of annealing time, the XRD peaks at 13.88° and 28.08° are stronger and stronger, and it can be seen from the Scherrer formula that the grains are getting bigger and bigger. Comparing the XRD data of FAPbI ₃ , the peaks at 13.88° and 28.08° are close to the (001) and (002) diffraction peaks of the three-dimensional perovskite, indicating that in the NFPI ₇ film, the larger the number of n components, the higher the crystallinity. The better, the closer to the three-dimensional FAPbI ₃ . In addition, weak diffraction peaks around 11.54°, 16.20°, 25.72° and 29.29° can be seen in the films annealed for 5 min and 10 min, corresponding to layered perovskite crystals with small n quantum well structures. However, these four diffraction peaks gradually disappeared under longer annealing time, indicating that the small-n quantum well composition (wide bandgap) decreased. Figure 11 shows atomic force microscopy (AFM) images of NFPI ₇ films at different annealing times. It can be seen that with the increase of annealing time, the roughness of the films gradually increases, but the R _rms parameter of all films is less than 5 nm, indicating that the NFPI ₇ material has good film-forming properties. It can be clearly seen from the AFM phase diagram that as the annealing time of the film increases from 0 min to 10 min, the grains gradually increase. Combined with the XRD pattern, the increased grains correspond to the large-n quantum well structure. It shows that the annealing treatment plays a role in regulating the quantum well structure.

Example 5 Devices based on multiple quantum well perovskite materials.

The device structure is shown in Figure 12. From bottom to top, it is transparent substrate 1-glass, cathode layer 2-ITO, electron transport layer 3-ZnO/PEIE, light-emitting layer 4-NFPI ₇ , hole transport layer 5-TFB and anode layer 6-MoO _x /Au. The specific preparation method is as follows:

(1) The transparent conductive substrate ITO glass is ultrasonically cleaned with acetone solution, ethanol solution and deionized water, and dried with dry nitrogen after cleaning. The sheet resistance of the ITO film of the anode layer is 15Ω/cm ² ;

(2) The dried substrate is moved into a vacuum chamber, and the ITO glass is subjected to ultraviolet ozone pretreatment for 10 minutes under an oxygen pressure environment;

(3) Spin-coat ZnO thin film on the treated ITO substrate, and then transfer to a 150°C heating table for annealing for 30min. Spin-coated PEIE film on ZnO film, annealed for 10 min, and then transferred to a nitrogen glove box;

(4) The precursor solution (NFPI ₇ ) with a molar ratio of C ₁₀ H ₇ CH ₂ NH ₃ I, NH ₂ CH=NH ₂ I (FAI) and PbI _{2 in a 2:1:2} molar ratio was spin-coated on ZnO/PEIE , annealed at 100 °C on a heating table, annealed for 0 min, 5 min, 10 min, 20 min, 30 min, and 60 min, respectively. After annealing, perovskite films with different multiple quantum well structures were obtained.

(5) The TFB solution was spin-coated on the NFPI ₇ film as a hole transport layer.

(6) After the preparation of each functional layer, the MoO _x /Au composite electrode was prepared. The gas pressure was 6×10 ^-7 Torr, and the evaporation rate was 0.1 nm/s. The evaporation rate and thickness were monitored by a film thickness meter.

(7) The prepared device was packaged in a glove box with a 99.9% nitrogen atmosphere.

(8) Test the current-voltage-radiation intensity characteristics of the device, and simultaneously test the luminescence spectrum parameters of the device.

Figure 13 is the electroluminescence (EL) spectrum of the light-emitting device prepared using the NFPI ₇ precursor. In the EL image, only the large n quantum well structure emits light, but there is no light emission from the small n quantum well structure in the PL image, indicating that when After being injected from the electrode, the carriers migrate to the large n quantum well structure as the center of radiative recombination luminescence. The light-emitting position of the device annealed for 5 min is around 768 nm, the light-emitting position of the device after annealing for 10 min is red-shifted to around 785 nm, and the light-emitting position of the device after annealing for 30 min is red-shifted to 787 nm, which is consistent with the PL spectrum of the film, indicating that the film with a long annealing time The content of medium and narrow band gap quantum wells increases, and the well width becomes wider. Figure 14 is the characteristic curve of voltage-current density-radiation intensity of NFPI ₇ multiple quantum well perovskite device. Several devices have very low turn-on voltage (less than 1.5V). After the device is turned on, the current density and radiation intensity The sharp rise indicates efficient carrier injection and migration efficiency in the device. Fig. 15 is a characteristic curve diagram of device current-external quantum efficiency. The external quantum efficiency of the device prepared after annealing the film for 10 min reaches the highest 8.6%.

It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (3)

1. A perovskite material multiple quantum well structure regulation and control method based on film post-processing is characterized in that the perovskite material multiple quantum well structure is regulated through a film post-processing process; the selected material is perovskite material capable of forming multiple quantum well structure by self-assembly, and the material is made of AX¹、BX²And MX³ ₂Prepared according to the molar ratio of a to b to c, wherein A is R^1-Y⁺，R^1-Is an aliphatic hydrocarbon group having 1 to 50 carbon atoms, an alicyclic hydrocarbon group having 5 to 100 carbon atoms, an optionally substituted aryl group having 6 to 100 carbon atoms or an optionally substituted heterocyclic group having 3 to 100 carbon atoms, Y⁺Is any one of amine and organic cation containing N heterocycle; b isMethylamine, formamidine or metal ions; m is a metal element; x¹X²X³Is a halogen element; the film post-treatment conditions were: one or the combination of heating annealing, solvent annealing and vacuum drying; the optimization of device efficiency can be realized through the regulation and control of a multi-quantum well structure; the heating and annealing conditions are as follows: placing the substrate coated with the precursor solution on a heating table for direct annealing, wherein the annealing temperature is determined by the type of the material and the substrate, and the time is 0-5 h; the solvent annealing conditions were: placing the substrate spin-coated with the precursor solution in a container keeping a solvent atmosphere for 0-24 h; the vacuum drying conditions were: and placing the substrate coated with the precursor solution in a vacuum chamber for 0-24 h.

2. The multiple quantum well structure regulation method of claim 1, wherein AX is¹Is C₁₀H₇CH₂NH₃I、C₁₀H₇CH₂NH₃Br、C₆H₅CH₂NH₃I、C₆H₅(CH₂)₂NH₃I、C₆H₅(CH₂)₄NH₃One of I, BX₂Is CH₃NH₃I、NH₂CH＝NH₂I、CsI、NH₂CH＝NH₂Br、NH₂CH＝NH₂Cl、CH₃NH₃Br、CH₃NH₃One of Cl, CsBr and CsCl, MX³ ₂Is PbI₂、PbBr₂、PbCl₂One of them.

3. Use of a modulation and control method according to claim 1 or 2, characterized in that the perovskite material multiple quantum well structure is modulated by a thin film post-treatment process.

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