CN111254402B - Intermediate belt film of Cr-doped ZnS and preparation method thereof - Google Patents

Intermediate belt film of Cr-doped ZnS and preparation method thereof Download PDF

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CN111254402B
CN111254402B CN202010164031.6A CN202010164031A CN111254402B CN 111254402 B CN111254402 B CN 111254402B CN 202010164031 A CN202010164031 A CN 202010164031A CN 111254402 B CN111254402 B CN 111254402B
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CN111254402A (en
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范文亮
姚海燕
吕笑公
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Ordos Institute of Technology
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    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C23C14/352—Sputtering by application of a magnetic field, e.g. magnetron sputtering using more than one target
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0623—Sulfides, selenides or tellurides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0623—Sulfides, selenides or tellurides
    • C23C14/0629—Sulfides, selenides or tellurides of zinc, cadmium or mercury
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/58—After-treatment
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    • C—CHEMISTRY; METALLURGY
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/58—After-treatment
    • C23C14/5893—Mixing of deposited material

Abstract

The invention discloses a middle belt film of Cr doped ZnS and a preparation method thereof2S3The target materials are respectively arranged on the target positions of a magnetron sputtering instrument, then the cleaned soda-lime glass substrate is fixed on an objective table, the vacuum pumping is carried out, and then ZnS and Cr are alternately sputtered in sequence2S3Depositing Cr-ZnS on a soda-lime glass substrate to obtain a laminated film, and finally putting the laminated film into an annealing furnace for annealing to finally obtain the Cr-ZnS intermediate band film. The Cr-ZnS film prepared by adopting the alternate magnetron sputtering method and annealing treatment under the protective atmosphere has a structure of mixing sphalerite and wurtzite, is positioned near 650nm and 459nm in a UV-vis-NIR light absorption spectrum, has two extra absorption peaks, shows that an intermediate band is formed in an original energy band structure, increases the light absorption coefficient and improves the light absorption intensity, and further provides a guide direction for the preparation of a Cr-ZnS intermediate band film solar cell.

Description

Intermediate belt film of Cr-doped ZnS and preparation method thereof
Technical Field
The invention relates to an intermediate band absorption layer material in the field of solar cells, in particular to a Cr-doped ZnS intermediate band thin film and a preparation method thereof.
Background
Since the 70's of the 20 th century, research into optical, electrical, structural, and magnetic properties of chromium-doped zinc sulfide (Cr-ZnS) has been initiated. Cr-ZnS has potential applications in the photoelectric and spintronic fields, such as: can be used as the laser material of near infrared and mid infrared lasers. Also known as dilute ferromagnetic semiconductors, ferromagnetism at room temperature has also been demonstrated.
In the prior art, research teams only theoretically find that Cr-ZnS can be used as an intermediate band (hereinafter referred to as IB) material for IB thin-film solar cells. Experimentally, Cr-ZnS thin films have been prepared by chemical water bath and laser deposition. However, the Cr-ZnS thin film prepared by the chemical water bath method and the laser deposition method has uneven crystal particle distribution inside and the light absorption intensity cannot meet the requirement.
Disclosure of Invention
Aiming at the problems existing in the prior technical scheme, the invention aims to provide the intermediate band film of Cr-doped ZnS and the preparation method thereof, so that the doped Cr-ZnS film is realized, Cr atoms are doped in a matrix semiconductor material to form IB, solar energy absorption is widened, charge recombination is inhibited, photovoltaic conversion is improved, and the light absorption intensity is obviously enhanced.
In order to achieve the purpose, the invention provides the following technical scheme:
preparation method of intermediate belt film of Cr-doped ZnS, wherein Cr is used for the film2S3Preparation of Cr by doping ZnS-based thin film material2S3The chemical molecular formula of the ZnS-based doped thin film material is Cr-ZnS, and the preparation method comprises the following steps:
step 1: preparing a ZnS target material;
step 2: preparation of Cr2S3A target material;
and step 3: cleaning the soda-lime glass substrate;
and 4, step 4: mixing ZnS target material with Cr2S3The target materials are respectively arranged on the target positions of the magnetron sputtering instrument;
and 5: fixing the cleaned soda-lime glass substrate on an objective table;
step 6: vacuumizing the sputtering environment, and alternately sputtering ZnS and Cr in sequence under the conditions that the gas flow of the sputtering medium Ar is 30sccm and the sputtering pressure is 0.6Pa2S3Target material was attached to a soda-lime glass substrate at a temperature of 30 deg.C, wherein each ZnS layer was deposited at a radio frequency power of 60W, 6 layers were deposited, and each C r layers were deposited2S3Depositing 6 layers by DC power supply of 60W, and finally obtaining Cr-ZnS prefabricated film, namely a laminated film, namely soda-lime glass/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3(ii)/Zn S; depositing to obtain a laminated film with the molecular formula of Cr-ZnS; the total six doped layers have the specific structure that: growing 80nm Cr-doped ZnS buffer layer on the first substrate, dopingThe impurity concentration is 1018cm-3Magnitude; growing a 300nm Cr-doped ZnS buffer layer on the second substrate with a doping concentration of 1018cm-3Magnitude; the thickness of the third layer and the fourth layer is respectively 30nm and 100 nm; the fifth layer and the sixth layer are formed by doping the ZnS absorbing layer with a doping concentration of 1019cm-3Magnitude and thickness of the film are both 80 nm;
and 7: and (4) putting the laminated film obtained in the step (6) into an annealing furnace in an Ar gas protective environment for annealing, and finally obtaining the Cr-ZnS intermediate band film.
As a further improvement of the above scheme, the step of cleaning the soda-lime glass substrate in step 3 is: cutting a soda-lime glass substrate → washing with a liquid detergent → deionized water ultrasonic treatment for 20min → soaking with 10% dilute sulfuric acid for 20min → deionized water cleaning → carbon tetrachloride ultrasonic treatment for 10min → acetone ultrasonic treatment for 10min → absolute ethyl alcohol ultrasonic treatment for 10min → placing in absolute ethyl alcohol for standby.
As a further improvement of the above scheme, the purity of Ar gas in the step 6 and the step 7 is more than 99.99 percent by volume.
As a further improvement of the above, Cr is present in step 62S3The sputtering time of each layer is 1.0-2.5min, and the sputtering time of each layer of ZnS is 15 min; the vacuum condition in step 6 was 5.0X 10-5Pa。
As a further improvement of the scheme, the annealing temperature in the step 7 is 300-500 ℃, the annealing time is 20min, and the heating rate is 15 ℃/min.
As a further improvement of the above scheme, the annealing temperature in step 7 is 500 ℃.
As a further improvement of the scheme, in the step 7, after the laminated film prepared in the step 6 is placed in an annealing furnace, one end of the laminated film is introduced with argon for protection, and the other end of the laminated film is sealed by deionized water.
As a further improvement of the above, ZnS target and Cr2S3The distance from the target to the object stage is 58-62 mm.
As a further improvement of the above scheme, the ZnS target and Cr2S3The purity of the target material is as originalThe sub-percentage is more than 99.99%.
The intermediate band thin film of Cr-doped ZnS provided by the invention adopts the Cr2S3The ZnS-doped intermediate band is prepared by a preparation method.
Compared with the prior art, the invention has the beneficial effects that:
(1) the Cr-ZnS film prepared by adopting the alternate magnetron sputtering method and annealing treatment under the protective atmosphere has a structure of mixing sphalerite and wurtzite, and in the UV-vis-NIR light absorption spectrum, in addition to the light absorption band edge response (the optical band gap is about 3.3eV) corresponding to ZnS, two additional absorption peaks appear and are positioned near 650nm and 459nm, which indicates that a partially filled intermediate band is formed. This introduces a plurality of intermediate bands, thereby increasing the light absorption intensity.
(2) The Cr-ZnS intermediate band film prepared by the method has uniform size distribution of the composition elements and the crystal particles on the surface of the film, and at least one intermediate impurity band can be formed, so that the light absorption intensity of the material is improved. Meanwhile, the matrix semiconductor Cr-ZnS prepared by the invention can absorb photons in the range of visible light-infrared light source, increase photon-generated carriers and reduce the recombination of electron-hole pairs, thereby enhancing the photocurrent.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a flow chart of a method for preparing an intermediate band film of Cr-doped ZnS according to the present invention.
FIG. 2 is XRD patterns of Cr-ZnS-1.5 intermediate band thin film samples prepared at different annealing temperatures in example 2 of the present invention.
FIG. 3 is an XRD pattern of Cr-ZnS thin films of different Cr contents annealed at 500 ℃ in accordance with the present invention.
FIG. 4 is an enlarged view of the diffraction peak of the (111) or (0010) crystal plane in FIG. 3 according to the present invention.
FIG. 5 shows Raman spectra of ZnS, Cr-ZnS-1.0, Cr-ZnS-1.5 and Cr-ZnS-2.5 thin films in accordance with an embodiment of the present invention.
FIG. 6 is an SEM image of Cr-ZnS thin films of the present invention annealed at 500 ℃ with different Cr contents.
FIG. 7 is an EDAX map of a ZnS thin film of the present invention.
FIG. 8 is an EDAX spectrum of a Cr-ZnS-1.5 intermediate band thin film in example 2 of the present invention.
FIG. 9 is a surface element distribution diagram of a Cr-ZnS-2.5 intermediate band thin film annealed at 500 ℃ in example 3 of the present invention.
FIG. 10 is a UV-vis-NIR absorption spectrum of thin films of ZnS and Cr-ZnS sample annealed at 500 ℃ in accordance with the invention.
FIG. 11 is a graph of transient photocurrent response of intermediate band films of annealed ZnS and Cr-ZnS samples of the present invention at 500 ℃.
In the figure: Cr-ZnS-1.0 is the sample number of the Cr-ZnS pre-formed laminated film prepared in example 1 of the present invention.
Cr-ZnS-1.5 is the sample number of the Cr-ZnS pre-formed laminated film prepared in example 2 of the present invention.
Cr-ZnS-2.5 is the sample number of the Cr-ZnS pre-formed laminated film prepared in example 3 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments.
Parameters of experimental target materials, auxiliary materials and reagents used in the examples of the present invention are shown in table 1:
TABLE 1
Figure GDA0003299791270000041
Figure GDA0003299791270000051
The specifications of the experimental equipment used in the examples of the present invention are shown in table 2:
TABLE 2
Figure GDA0003299791270000052
Wherein, the used analysis test method comprises the following steps:
x-ray diffractometer (XRD): the crystallinity and crystal structure of the film samples were characterized and qualitatively analyzed with a sweep ranging from 20 ° to 80 °.
Raman spectroscopy (Raman spectra): the vibration mode of each chemical bond in the molecular structure is characterized, and the excitation wavelength is 514 nm.
Scanning Electron Microscope (SEM): and characterizing the surface and cross-sectional structure forms of the film sample, and testing the element distribution and content of the film by EDAX matched with the surface and cross-sectional structure forms.
X-ray photoelectron spectrometer (XPS): the composition of the film and the chemical morphology of the elements were tested.
Ultraviolet-visible spectrophotometer (UV-vis): the absorption and reflection spectra of the film are measured, and optical characteristics such as absorption coefficient and forbidden bandwidth are obtained by analyzing the spectra.
Photocurrent response detection: the incident light is mechanically switched by placing and removing a barrier between the lamp and the sample while the photocurrent is detected.
Example 1
Referring to the preparation flow of fig. 1, the method for preparing the intermediate band film of Cr-doped ZnS of the present embodiment includes the following steps:
step 1: preparing a ZnS target material; a circular target with the diameter of 65mm is selected, the purity is 99.99%, and the thickness is 5 mm. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
Step 2: preparation of Cr2S3A target material; selecting Cr with the thickness of 3mm and the purity of 99.99 percent2S3. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
And step 3: cleaning a soda-lime glass substrate, firstly cutting the soda-lime glass substrate into 2cm multiplied by 2cm, cleaning surface smudge sundries by using detergent, then carrying out ultrasonic treatment for 20min by using deionized water, then soaking the substrate for 20min by using 10% dilute sulfuric acid, taking out the soda-lime glass substrate, and cleaning the substrate by using the deionized water; sequentially putting the cleaned soda-lime glass substrate into carbon tetrachloride, acetone and absolute ethyl alcohol for alternative ultrasound for 10 min; and finally, putting the soda-lime glass substrate subjected to ultrasonic processing into absolute ethyl alcohol for later use. The ultrasonic cleaner is a cleaner with a model number KQ-250E of ultrasonic instruments Limited in Kunshan.
And 4, step 4: preparation of Cr-ZnS intermediate band film
(1) ZnS (thickness 5mm) and Cr of a circular target with the diameter of 65mm2S3Target materials (thickness 3mm) were mounted to the magnetron sputter target sites, respectively, with ZnS mounted to a strong magnetic target site and sputtered using a Radio Frequency (RF) source. The magnetron sputtering instrument adopts a magnetron sputtering instrument of Fu-10Sp model of Fulin scientific engineering Co;
(2) a cleaned Soda Lime Glass (SLG) substrate was fixed on a stage using a stage apparatus model ET200 from Shanghai Shoyuan instruments Ltd. The distance from the target to the step instrument is 60 mm;
(3) vacuumizing the sputtering environment, and setting the background vacuum degree to be 5.0 multiplied by 10-5Pa；
(4) Alternately sputtering ZnS and Cr in sequence under the conditions of a sputtering medium Ar (purity 99.99%) with a gas flow rate of 30sccm and a working pressure of 0.6Pa2S3And depositing Cr-ZnS on a soda-lime glass substrate at a temperature of 30 ℃ to obtain a laminated film. The specific method comprises depositing each Z nS layer and 6 Cr layers under 60W RF power2S35 layers were co-deposited by DC power supply of 60W, and finally, Cr-ZnS pre-formed film, i.e. laminated film: SLG/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/ Cr2S3/ZnS/Cr2S3(ii) ZnS; wherein the sputtering ZnS comprises 6 layers, each layer has a sputtering time of 15min, and Cr2S3The total number of the layers is 6, and the sputtering time of each layer is 1.0 min.
And 5: inserting the quartz tube containing the prefabricated film into an annealing furnace, wherein the annealing furnace is a vacuum tube type annealing furnace of a GsL-1100X model of the combined fertilizer and crystal material technology Limited company, introducing argon into one end of the annealing furnace, sealing the other end by using deionized water, rapidly annealing under an argon protection environment and at different annealing temperatures, wherein the annealing temperatures are respectively 300 ℃, 400 ℃, 450 ℃ and 500 ℃, the annealing time is 20min, and the heating rate is 15 ℃/min. Finally obtaining a Cr-ZnS intermediate band film; as a sample of a pre-formed laminated film of the reference Cr-ZnS-1.0.
Example 2
Referring to fig. 1, the preparation method of the intermediate band film of Cr-doped ZnS of the present embodiment includes the following steps:
step 1: preparing a ZnS target material; a circular target with the diameter of 65mm is selected, the purity is 99.99%, and the thickness is 5 mm. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
Step 2: preparation of Cr2S3A target material; selecting Cr with the thickness of 3mm and the purity of 99.99 percent2S3. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
And step 3: cleaning a soda-lime glass substrate, firstly cutting the soda-lime glass substrate into 2cm multiplied by 2cm, cleaning surface smudge sundries by using detergent, then carrying out ultrasonic treatment for 20min by using deionized water, then soaking the substrate for 20min by using 10% dilute sulfuric acid, taking out the soda-lime glass substrate, and cleaning the substrate by using the deionized water; sequentially putting the cleaned soda-lime glass substrate into carbon tetrachloride, acetone and absolute ethyl alcohol for alternative ultrasound for 10 min; and finally, putting the soda-lime glass substrate subjected to ultrasonic processing into absolute ethyl alcohol for later use. The ultrasonic cleaner is a cleaner with a model number KQ-250E of ultrasonic instruments Limited in Kunshan.
And 4, step 4: preparation of Cr-ZnS intermediate band film
(1) ZnS (thickness 5mm) and Cr of a circular target with the diameter of 65mm2S3Target materials (thickness 3mm) were mounted to the magnetron sputter target sites, respectively, with ZnS mounted to a strong magnetic target site and sputtered using a Radio Frequency (RF) source. The magnetron sputtering instrument adopts a magnetron sputtering instrument of Fu-10Sp model of Fulin scientific engineering Co;
(2) a cleaned Soda Lime Glass (SLG) substrate was fixed on a stage using a stage apparatus model ET200 from Shanghai Shoyuan instruments Ltd. The distance from the target to the step instrument is 60 mm;
(3) vacuumizing the sputtering environment, andbackground vacuum was set to 5.0X 10-5Pa；
(4) Alternately sputtering ZnS and Cr in this order under conditions of a sputtering medium Ar (purity 99.99%) flow rate of 30sccm and a working pressure of 0.6P a2S3And depositing Cr-ZnS on a soda-lime glass substrate at a temperature of 30 ℃ to obtain a laminated film. The specific method comprises depositing ZnS layer and Cr layer at 60W RF power2S36 layers were co-deposited by DC power supply of 60W, and finally, Cr-ZnS pre-formed film, i.e. laminated film: SLG/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/ Cr2S3(ii) ZnS; wherein the sputtering ZnS comprises 6 layers, each layer has a sputtering time of 15min, and Cr2S3The total number of the layers is 6, and the sputtering time of each layer is 1.5 min.
And 5: inserting the quartz tube containing the prefabricated film into an annealing furnace, wherein the annealing furnace is a vacuum tube type annealing furnace of a GsL-1100X model of the combined fertilizer and crystal material technology Limited company, introducing argon into one end of the annealing furnace, sealing the other end by using deionized water, rapidly annealing under an argon protection environment and at different annealing temperatures, wherein the annealing temperatures are respectively 300 ℃, 400 ℃, 450 ℃ and 500 ℃, the annealing time is 20min, and the heating rate is 15 ℃/min. Finally obtaining a Cr-ZnS intermediate band film; as a sample of a prefabricated laminated film of the reference Cr-ZnS-1.5.
Example 3
Referring to fig. 1, the preparation method of the intermediate band film of Cr-doped ZnS of the present embodiment includes the following steps:
step 1: preparing a ZnS target material; a circular target with the diameter of 65mm is selected, the purity is 99.99%, and the thickness is 5 mm. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
Step 2: preparation of Cr2S3A target material; selecting Cr with the thickness of 3mm and the purity of 99.99 percent2S3. The manufacturer: beijing Xinyou Jingmai Shuang Co Ltd.
And step 3: cleaning a soda-lime glass substrate, firstly cutting the soda-lime glass substrate into 2cm multiplied by 2cm, cleaning surface smudge sundries by using detergent, then carrying out ultrasonic treatment for 20min by using deionized water, then soaking the substrate for 20min by using 10% dilute sulfuric acid, taking out the soda-lime glass substrate, and cleaning the substrate by using the deionized water; sequentially putting the cleaned soda-lime glass substrate into carbon tetrachloride, acetone and absolute ethyl alcohol for alternative ultrasound for 10 min; and finally, putting the soda-lime glass substrate subjected to ultrasonic processing into absolute ethyl alcohol for later use. The ultrasonic cleaner is a cleaner with a model number KQ-250E of ultrasonic instruments Limited in Kunshan.
And 4, step 4: preparation of Cr-ZnS intermediate band film
(1) ZnS (thickness 5mm) and Cr of a circular target with the diameter of 65mm2S3Target materials (thickness 3mm) were mounted to the magnetron sputter target sites, respectively, with ZnS mounted to a strong magnetic target site and sputtered using a Radio Frequency (RF) source. The magnetron sputtering instrument adopts a magnetron sputtering instrument of Fu-10Sp model of Fulin scientific engineering Co;
(2) a cleaned Soda Lime Glass (SLG) substrate was fixed on a stage using a stage apparatus model ET200 from Shanghai Shoyuan instruments Ltd. The distance from the target to the step instrument is 60 mm;
(3) vacuumizing the sputtering environment, and setting the background vacuum degree to be 5.0 multiplied by 10-5Pa；
(4) Alternately sputtering ZnS and Cr in this order under conditions of a sputtering medium Ar (purity 99.99%) flow rate of 30sccm and a working pressure of 0.6P a2S3And depositing Cr-ZnS on a soda-lime glass substrate at a temperature of 30 ℃ to obtain a laminated film. The specific method comprises depositing ZnS layer and Cr layer at 60W RF power2S36 layers were co-deposited by DC power supply of 60W, and finally, Cr-ZnS pre-formed film, i.e. laminated film: SLG/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/ Cr2S3(ii) ZnS; wherein the sputtering ZnS comprises 6 layers, each layer has a sputtering time of 15min, and Cr2S3The total number of the layers is 6, and each layer is sputtered for 2.5 min.
And 5: inserting the quartz tube containing the prefabricated film into an annealing furnace, wherein the annealing furnace is a vacuum tube type annealing furnace of a GsL-1100X model of the combined fertilizer and crystal material technology Limited company, introducing argon into one end of the annealing furnace, sealing the other end by using deionized water, rapidly annealing under an argon protection environment and at different annealing temperatures, wherein the annealing temperatures are respectively 300 ℃, 400 ℃, 450 ℃ and 500 ℃, the annealing time is 20min, and the heating rate is 15 ℃/min. Finally obtaining a Cr-ZnS intermediate band film; as a sample of a prefabricated laminated film of the reference Cr-ZnS-2.5.
On the basis of the embodiment, the ZnS prefabricated film is prepared by a sputtering method, the number of the ZnS prefabricated film is 6, and the sputtering time of each layer is 15 min; as a comparative film sample.
And carrying out diffraction analysis on the obtained Cr-ZnS intermediate band film by using an X-ray diffractometer (hereinafter referred to as XRD), and simultaneously characterizing the crystallinity and the crystal structure of a film sample and carrying out qualitative analysis on the film sample:
first, phase structure analysis
Referring to fig. 2, first, we investigated the crystal phase structure of the Cr-ZnS thin film samples. FIG. 2 is an XRD spectrum of a Cr-ZnS-1.5 thin film sample prepared by annealing at 300-500 ℃. Similar results were obtained for the Cr-ZnS thin film samples of examples 1 and 3, which are not shown. As can be seen, with the increase of the annealing temperature, only 4 diffraction peaks are obvious, and the peaks are gradually enhanced, which shows that the size of the crystal grains is also gradually increased.
The samples were compared to the JCPDS card for sphalerite ZnS Standard XRD (accession number 05-0566) and the JCPDS card for wurtzite ZnS (accession number 12-0688), respectively, and are likely to have both sphalerite and wurtzite structures. When the annealing temperature is increased to 500 ℃ or higher, the thin film is peeled off from the substrate, and considering the influence of the crystal grain size on the photoelectric characteristics thereof, it is judged that the annealing temperature is 500 ℃ as the most suitable.
See fig. 3, which is an XRD pattern of Cr-ZnS thin films with different Cr contents. As can be seen from the figure, the undoped matrix material ZnS also has a weak diffraction peak at the position of about 26.9 degrees 2 theta, which indicates that the sample has a wurtzite structure, other miscellaneous peaks do not appear along with the increase of the Cr content, but the main diffraction peak is weakened, and the half height width of the main peak is increased, which indicates that the crystal size is reduced, because the Cr atoms start to grow in the crystalThe function of the nucleation centers is that the higher the Cr content is, the more the nucleation centers are, and the smaller the crystal particles are. As can be seen from the enlarged view of the diffraction peak of the (111) or (0010) crystal plane (see FIG. 4), as the Cr content increases, the peak position shifts toward a small angle direction, indicating that Cr has been doped into ZnS and that Cr ions exist in the form of +3 valence because only Cr3+Ionic radius greater than Zn2+The ionic radius is the radius of the ion, which results.
Referring to fig. 5, to confirm the structure of the Cr-ZnS thin film sample more accurately, we tested the raman spectrum of the sample, as shown in fig. 5. When observed from a Raman spectrum, compared with the matrix material before doping, the ZnS matrix material has no other Raman peaks after doping, which shows that the crystal structures of the ZnS matrix material before and after doping are the same. 4 obvious Raman peaks appear in the spectrum, wherein the peak positions are 295 and 347cm-1Corresponding to the sphalerite and wurtzite structures respectively, and the peak position is 219cm-1Corresponding to both structures. The sample is shown to have two crystal structures of sphalerite and wurtzite.
In conclusion, by utilizing the preparation method of the Cr-doped ZnS intermediate band film, the prepared Cr-ZnS sample film has two crystal structures of sphalerite and wurtzite simultaneously through phase analysis.
Second, analysis of absorption layer morphology
See fig. 6, which is an SEM image of Cr-ZnS thin films of different Cr contents obtained after annealing at 500 c for 20 minutes. As can be seen, the film surface was smooth, but in the undoped ZnS film, clusters on the surface were also observed. When the Cr element is doped, crystal particles with uniform sizes are uniformly distributed on the surface of the film, and the size of the crystal particles on the surface is reduced along with the increase of the doping amount. This is consistent with X-ray diffraction test structures.
Element test and component analysis of absorption layer
See FIGS. 7 and 8 for EDAX spectra of ZnS and Cr-ZnS-1.5 thin films, respectively. It can be determined that the Cr-ZnS-1.5 sample only contains Cr, Zn and S elements. The relative amounts and proportions of the elements in the sample can be determined in conjunction with table 3. Table 3 shows the chemical composition of Cr-ZnS thin film of the sample annealed at 500 ℃ shown in Table 3 along with Cr2S3The Cr-ZnS samples were prepared at different sputtering times, and when the sputtering time was 1.0 minute, the ratio of Cr/(Zn + Cr) was 4.2%; when the sputtering time is 1.5 minutes, the ratio is 5.1 percent; when the sputtering time was 2.5 minutes, the ratio was again 6.9%. Each sample was substantially in accordance with the theoretical stoichiometric ratio. Moreover, as can be seen from the element distribution diagram (see figure 9) on the surface of the Cr-ZnS-2.5 film, the elements are uniformly distributed and have no element agglomeration phenomenon.
TABLE 3
Figure GDA0003299791270000121
In conclusion, through the absorption layer morphology analysis, the absorption layer element test and the component analysis, the conclusion is that the Cr-ZnS sample film prepared by the method for preparing the intermediate band film by doping the Cr with the ZnS has uniform distribution of all elements and no element agglomeration phenomenon.
Fourthly, analysis and research of photoelectric properties of absorption layer
See FIG. 10 for UV-vis-NIR absorption spectra of annealed ZnS and multi-set Cr-ZnS sample films at 500 ℃. We can clearly see that the optical band gap of the matrix material ZnS is about 3.3eV, the absorption coefficient of Cr-doped ZnS increases compared to undoped ZnS, and the overall increase in light absorption intensity with increasing doping indicates that the film absorbs more photons, and that there are two broader absorption peaks appearing around 1.9eV (650nm) and 2.7eV (459nm), indicating that there are two IB formations. The two absorption peaks and the octahedral coordination sites of Cr3+It is stated that the doped Cr ions enter into the interstitial sites of the ZnS lattice or into the sites of Zn ions, thereby leading to an enhancement of absorption in the infrared region.
See FIG. 11, which is a graph of transient photocurrent response lines of annealed ZnS and Cr-ZnS sample films at 500 ℃ using a standard solar simulator periodic switching light source with a light intensity of 100mW/cm2The period was 20 seconds, with 10 seconds light and 10 seconds dark, obtained by irradiating the sample test. When bright, the photoreduction current increases rapidly, and after a few seconds, the photocurrent becomes stableIn the dark state, the photocurrent is instantaneously reduced. For Cr-ZnS thin films, the photocurrent was much greater than ZnS. The increase in photocurrent is due to the broad spectral response produced by the IB effect, which produces more photogenerated carriers. With the lapse of time, the current slow-changing phenomenon existing in the bright area in the sample is gradually weakened, which indicates that the occurrence probability of the surface recombination process is reduced. The transient response test of sample photocurrent further verifies that IB is formed in the base semiconductor material by doping, so that the solar energy absorption is widened, the charge recombination is inhibited, and the photovoltaic conversion is improved.
Meanwhile, as can be seen from the figure, in three transient photocurrent response spectral lines of Cr-ZnS-1.0, Cr-ZnS-1.5 and Cr-ZnS-2.5, the samples with different Cr contents have the same change trend, but the photocurrent enhancement amplitude in the case of bright light is large along with the increase of the Cr content. The phenomenon that the matrix semiconductor ZnS can absorb photons in the range of visible light-infrared light sources by doping Cr element and increase photon-generated carriers to reduce the recombination of electron-hole pairs so as to enhance the photocurrent is proved again that the Cr element can form IB in the Cr-ZnS sample energy band structures of sphalerite and wurtzite crystal structures.
The above analysis shows that Cr is in the prepared Cr-ZnS crystal structure3+Partially replace Zn2+And a median band is induced. According to theoretical calculations for a Cr-ZnS absorber layer, this band is mainly contributed by the dxy, dxz and dyz states of Cr atoms, the p state of S atoms is also weakly contributed, Zn atoms do not contribute to it, and in addition the IB is metallic across the fermi level, partially filled.
Combining the above examples and the analysis of the data shown in the figures, the present invention employs an alternative magnetron sputtering method in combination with annealing treatment under a protective atmosphere to produce a Cr-ZnS thin film having a structure in which sphalerite and wurtzite are mixed, and in the UV-vis-NIR absorption spectrum thereof, in addition to the light absorption band edge response corresponding to ZnS (optical band gap of about 3.3eV), two additional absorption peaks appear, located near 650nm and 459nm, indicating the formation of a partially filled intermediate band. This introduces a plurality of intermediate bands, thereby increasing the light absorption intensity.
In addition, the Cr-ZnS intermediate band film prepared by the method has uniform size distribution of the composition elements and the crystal particles on the surface of the film, and at least one intermediate impurity band can be formed, so that the light absorption intensity of the material is improved. Meanwhile, the matrix semiconductor Cr-ZnS prepared by the invention can absorb photons in the range of visible light-infrared light source, increase photon-generated carriers and reduce the recombination of electron-hole pairs, thereby enhancing the photocurrent.
The foregoing is merely exemplary and illustrative of the present invention and various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the scope of the present invention as defined in the accompanying claims.

Claims (10)

1. The preparation method of the intermediate belt film of the Cr-doped ZnS is characterized in that the film uses Cr2S3Preparation of Cr by doping ZnS-based thin film material2S3The chemical molecular formula of the ZnS-based doped thin film material is Cr-ZnS, and the preparation method comprises the following steps:
step 1: preparing a ZnS target material;
step 2: preparation of Cr2S3A target material;
and step 3: cleaning the soda-lime glass substrate;
and 4, step 4: mixing ZnS target material with Cr2S3The target materials are respectively arranged on the target positions of the magnetron sputtering instrument;
and 5: fixing the cleaned soda-lime glass substrate on an objective table;
step 6: vacuumizing the sputtering environment, and alternately sputtering ZnS and Cr in sequence under the conditions that the gas flow of the sputtering medium Ar is 30sccm and the sputtering pressure is 0.6Pa2S3The target material is put on a soda-lime glass substrate with the temperature of 30 ℃, wherein each ZnS layer is deposited under the radio frequency power of 60W, 6 Cr layers are deposited, and each Cr layer2S3Depositing 6 layers by DC power supply of 60W, and finally obtaining Cr-ZnS prefabricated film, namely a laminated film, namely soda-lime glass/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3/ZnS/Cr2S3(ii) ZnS; depositing to obtain a laminated film with the molecular formula of Cr-ZnS; the total six doped layers have the specific structure that: growing 80nm Cr-doped ZnS buffer layer with doping concentration of 10 on the first substrate18cm-3Magnitude; growing a 300nm Cr-doped ZnS buffer layer on the second substrate with a doping concentration of 1018cm-3Magnitude; the thickness of the third layer and the fourth layer is respectively 30nm and 100 nm; the fifth layer and the sixth layer are formed by doping the ZnS absorbing layer with a doping concentration of 1019cm-3Magnitude and thickness of the film are both 80 nm;
and 7: and (4) putting the laminated film obtained in the step (6) into an annealing furnace in an Ar gas protective environment for annealing, and finally obtaining the Cr-ZnS intermediate band film.
2. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: the step of cleaning the soda-lime glass substrate in the step 3 is as follows: cutting a soda-lime glass substrate → washing with a liquid detergent → deionized water ultrasonic treatment for 20min → soaking with 10% dilute sulfuric acid for 20min → deionized water cleaning → carbon tetrachloride ultrasonic treatment for 10min → acetone ultrasonic treatment for 10min → absolute ethyl alcohol ultrasonic treatment for 10min → placing in absolute ethyl alcohol for standby.
3. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: the purity of Ar gas in the step 6 and the step 7 is more than 99.99 percent by volume.
4. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: cr in step 62S3The sputtering time of each layer is 1.0-2.5min, and the sputtering time of each layer of ZnS is 15 min; the vacuum condition in step 6 was 5.0X 10-5Pa。
5. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: the annealing temperature in the step 7 is 300-500 ℃, the annealing time is 20min, and the heating rate is 15 ℃/min.
6. The method for preparing an intermediate band film of Cr-doped ZnS as claimed in claim 5, wherein: the annealing temperature in step 7 was 500 ℃.
7. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: and 7, after the laminated film prepared in the step 6 is placed in an annealing furnace, introducing argon into one end of the laminated film for protection, and sealing the other end of the laminated film by using deionized water.
8. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: ZnS target and Cr2S3The distance from the target to the object stage is 58-62 mm.
9. The method for preparing an intermediate band film of Cr-doped ZnS according to claim 1, wherein: the ZnS target and Cr2S3The purity of (A) is more than 99.99 atomic percent.
10. An intermediate band film of Cr doped ZnS, which adopts Cr2S3A method for producing a doped ZnS intermediate band, characterized in that the method is the method according to any one of claims 1 to 9.
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CN101781753A (en) * 2010-04-16 2010-07-21 贵州大学 Technological method for preparing Cr-doped beta-FeSi2 films
CN103103479A (en) * 2013-01-31 2013-05-15 浙江大学 Method for preparing p-type zinc oxide film through sulfur and nitrogen co-doping
CN103928576A (en) * 2014-05-09 2014-07-16 攀枝花学院 SnS/ZnS lamination thin film solar cell manufacturing method
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