METHOD FOR LASER DEPOSITION OF ORGANIC MATERIAL FILM OR ORGANIC-INORGANIC COMPOSITE MATERIAL FILM AND LASER DEPOSITION APPARATUS
20170268094 · 2017-09-21
Assignee
Inventors
- Tetsuhiko MIYADERA (Tsukuba-shi, JP)
- Takeshi SUGITA (Tsukuba-shi, JP)
- Takurou MURAKAMI (Tsukuba-shi, JP)
- Masayuki CHIKAMATSU (Tsukuba-shi, JP)
- Koji MATSUBARA (Tsukuba-shi, JP)
Cpc classification
Y02E10/542
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
Abstract
A method of laser-depositing at least one type of organic material, characterized in that a duty ratio of a laser that evaporates the organic material is adjusted, which addresses the problem of providing an organic material deposition method and deposition apparatus that solve the issues in the conventional art, such as the organic material vaporizing and contaminating the other raw materials to be deposited, and the film formation rate running out of control, and whereby the film formation rate and the evaporation rate can be stably adjusted and controlled. Additionally, the invention is characterized in that the duty ratio is adjusted based on the evaporation rate of the organic substance or the vapor pressure inside the vacuum chamber used for deposition.
Claims
1-7. (canceled)
8. A laser deposition method for film formation of an organic-inorganic composite perovskite on a substrate, comprising: irradiating an organic material with a laser beam to evaporate the organic material and irradiating an inorganic material with a laser beam to evaporate the inorganic material, and codepositing the organic material and the inorganic material with the substrate and thereby film forming the organic-inorganic composite perovskite on the substrate; wherein the organic material is a halide of an organic cation; and the inorganic material is MX.sub.2, where M is a divalent metal ion and X is at least one halogen selected from the group consisting of F, Cl, Br and I.
9. The laser deposition method according to claim 8, wherein the laser beam irradiated to the organic material is a pulsed laser beam having an adjustable duty ratio; and the duty ratio of the laser beam irradiated to the organic material is adjusted based on an evaporation rate of the organic material.
10. The laser deposition method according to claim 8, wherein the substrate, the organic material and the inorganic material are held inside a vacuum chamber; the laser beam irradiated to the organic material is a pulsed laser beam having an adjustable duty ratio; and the duty ratio of the laser beam irradiated to the organic material is adjusted based on a vapor pressure inside the vacuum chamber.
11. The laser deposition method according to claim 8, wherein the laser beam irradiated to the organic material is a pulsed laser beam with laser pulses having adjustable pulse widths and amplitudes; and the laser beam irradiated to the inorganic material is either a continuous-wave laser beam having an adjustable power or a pulsed laser beam having an adjustable duty ratio.
12. The laser deposition method according to claim 8, wherein the codeposited organic-inorganic composite perovskite is represented by formula (1) or formula (2):
AMX.sub.3 (1)
B.sub.2MX.sub.4 (2) where A and B represent organic cations, M represents a divalent metal ion, and X represents a halogen.
13. The laser deposition method according to claim 12, wherein A is CH.sub.3NH.sub.3.sup.+; B is R.sup.1NH.sub.3.sup.+, where R.sup.1 has two or more carbon atoms and is an alkyl group, an alkenyl group, an aralkyl group or an aryl group; and M is any one of Pb, Sn or Ge.
14. A laser deposition apparatus for film formation of an organic-inorganic composite perovskite by codepositing an organic material and an inorganic material on a substrate, wherein the organic material is a halide of an organic cation and an inorganic material is MX.sub.2 where M is a divalent metal ion and X is at least one halogen selected from the group consisting of F, Cl, Br and I; the laser deposition apparatus comprising: a vacuum chamber; a laser for irradiating the organic material and evaporating the organic material provided within the vacuum chamber; and a laser for irradiating the inorganic material and evaporating the inorganic material provided within the vacuum chamber.
15. The laser deposition apparatus according to claim 14, further comprising: evaporation rate measuring means for the organic material; and duty ratio adjusting means for adjusting a duty ratio of the first laser based on an evaporation rate measured by the evaporation rate measuring means.
16. The laser deposition apparatus according to claim 14, further comprising: vapor pressure measuring means for measuring a vapor pressure inside the vacuum chamber used for deposition; and duty ratio adjusting means for adjusting a duty ratio of the laser that evaporates the organic material, based on the vapor pressure measured by the vapor pressure measuring means.
17. A production method for an organic-inorganic composite perovskite film by film formation of the organic-inorganic composite perovskite on a substrate, comprising: irradiating an organic material with a laser beam to evaporate the organic material and irradiating an inorganic material with a laser beam and thereby evaporating the inorganic material, and codepositing the organic material and the inorganic material with the substrate and thereby film forming the organic-inorganic composite perovskite on the substrate; wherein the organic material is a halide of an organic cation; and the inorganic material is MX.sub.2, where M is a divalent metal ion and X is at least one halogen selected from the group consisting of F, Cl, Br and I.
18. The production method for an organic-inorganic composite perovskite film according to claim 17, wherein the organic/inorganic composite perovskite is represented by formula (1) or formula (2):
AMX.sub.3 (1)
B.sub.2MX.sub.4 (2) where A and B represent organic cations, M represents a divalent metal ion, and X represents a halogen.
19. The production method for an organic-inorganic composite perovskite film according to claim 18, wherein A is CH.sub.3NH.sub.3.sup.+; B is R.sup.1NH.sub.3.sup.+, where R.sup.1 has two or more carbon atoms and is one selected from the group consisting of an alkyl group, an alkenyl group, an aralkyl group and an aryl group; and M is any one selected from the group consisting of Pb, Sn and Ge.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
DESCRIPTION OF EMBODIMENTS
[0026]
[0027] The laser deposition method of the present invention involves laser deposition of at least one type of organic material, and is characterized by adjusting the duty ratio (ON time/(ON time+OFF time) or pulse width/pulse period) of the laser used to evaporate the organic material.
[0028] In the example in
[0029] The organic material used in the present invention is not limited, but examples include halogenated alkylamines such as iodinated methylamine and iodinated ethylamine, aralkylamine halides such as phenylethylamine iodides, and halogenated formamines such as iodinated formamine.
[0030] Such low-molecular-weight (molecular weights of about 200 or less, though not limited thereto) organic materials generally have a high vapor pressure compared to inorganic materials such as metals and oxides. Thus, in conventional vacuum deposition methods using heater-heated temperature control, there were problems in that vaporization could occur in the vacuum chamber and greatly degrade the vacuum level, or the film formation rate could run out of control. However, in the present invention, the organic material is laser-deposited and the duty ratio of the laser is adjusted. Therefore, vaporization such as that mentioned above can be greatly reduced, and the directionality of the deposition flux and the film formation rate can be controlled.
[0031] In the laser deposition of the present invention, any publicly known type of laser can be used for evaporating the organic material, as long as the duty ratio can be adjusted. However, a laser for which the amplitude (laser output) of the laser pulse can be adjusted is preferable. While the type of laser is not limited, examples include KrF excimer lasers (wavelength 248 nm). Nd:YAG lasers (wavelength 355 nm) and infrared lasers (wavelength 808 nm, 850 nm, 980 nm, etc.). For the organic material, an infrared laser is preferably used.
[0032] Although the frequency of the laser pulse is not limited, it may, for example, be 1-500 Hz.
[0033] The duty ratio may be adjusted by means of publicly known means such as adjustment of the pulse width.
[0034] With the laser deposition method of the present invention, the duty ratio may be adjusted to a predetermined value or within a predetermined numerical range in accordance with the type of organic material used and the laser pulse amplitude. However, by observing the evaporation rate of the organic material or the vapor pressure inside the vacuum chamber used for deposition and adjusting the duty cycle based on the observed values, it is possible to stably control the evaporation rate and the film formation rate without requiring much consideration of the type of organic material or the like.
[0035] As the means for observing the evaporation rate of the organic material, it is possible to use, for example, a crystal oscillator film thickness meter that is provided near the path of the evaporation flux and that measures the film thickness of the deposition film, and a means for taking the time derivative of the deposition film thickness evolution obtained by the film thickness meter, though the invention is not limited to such an embodiment. While it is preferable to provide a film thickness meter such as a crystal oscillator film thickness meter that corresponds to only the organic material being deposited, it may be shared with the other inorganic material being deposited in the case of codeposition, and may measure the film thickness of the total deposition film of the organic material and the inorganic material. If the laser power used for the inorganic material is constant, the evaporation rate of the inorganic material can be expected to remain approximately constant even if the duty ratio of the laser used for the organic material is adjusted. Therefore, by determining, beforehand, the evaporation rate of the inorganic material when the laser power used for the inorganic material is constant, and measuring the film thickness evolution of the total deposition film of the organic material and the inorganic material under conditions in which the laser power used for the inorganic material is held constant, the evaporation rate of the organic material can be estimated by subtracting the deposition rate of the inorganic material from the total deposition rate of the organic material and the inorganic material obtained by taking the time derivative of the film thickness evolution. The evaporation rate measuring means for the organic material in the present invention includes means for estimating the evaporation rate of the organic material in such a manner.
[0036] The vapor pressure measuring means that observes the vapor pressure inside the vacuum chamber being used for deposition can be chosen, as appropriate, from among those that are publicly known
[0037] While the adjustment of the duty ratio based on observations of the evaporation rate of the organic material or the vapor pressure inside the vacuum chamber used for deposition may be performed manually by an operator, it is preferable to provide an evaporation rate or vapor pressure measuring means, and a duty ratio adjusting means that automatically adjusts the duty ratio based on the measured values thereof.
[0038] The target material (the material to be deposited in the laser deposition method) used in the laser deposition method of the present invention may be a single type of organic material, but the laser deposition may involve codeposition using two or more types of organic materials as the target materials, or codeposition using an organic material and an inorganic material as the target materials. In the case of laser deposition in which codeposition is performed using an inorganic material as the target material, it is possible to use a laser for which the duty ratio can be adjusted, as mentioned above, as the laser for depositing the inorganic material. However, it is also possible to use a laser for which the duty cycle cannot be adjusted, e.g., a continuous-wave laser beam, as long as the power is adjustable. In order to achieve good film quality in the formed thin film, it is preferable to use a laser in which the duty ratio can be adjusted, similar to that used for the organic material.
[0039] As the inorganic material to be codeposited with the organic material, it is possible to use any publicly known inorganic material that is used for deposition.
[0040] The laser deposition method of the present invention, particularly when applied to the production of an organic-inorganic composite perovskite, is capable of effectively adjusting the evaporation rate and film formation rate of organic materials having high vapor pressures, so the method is able to stably produce, for a long time, an organic-inorganic composite perovskite of good quality.
[0041] Examples of such organic-inorganic composite perovskites, while not limiting, include those represented by formulas (1) and (2):
AMX.sub.3 (1)
B.sub.2MX.sub.4 (2)
where A and B represent organic cations, M represents a divalent metal ion, and X represents a halogen. Examples of the organic cation A include CH.sub.3NH.sub.3.sup.+, CH(NH.sub.2).sub.2.sup.+ and the like, and examples of the organic cation B include R.sup.1NH.sub.3, where R.sup.1 has two or more carbon atoms and is an alkyl group, an alkenyl group, an aralkyl group or an aryl group.
[0042] M is a divalent metal ion, such as Pb, Sn or Ge.
[0043] X is a halogen and is selected from among F, Cl, Br and I.
[0044] Of the target materials when forming a film of an organic-inorganic composite perovskite by laser codeposition in this manner, examples of the organic material constituting A include, but are not limited to, halogenated methylamines such as iodinated methylamine and halogenated formamidylamines such as iodinated formamidylamine. Examples of the organic material constituting B include, but are not limited to, halogenated alkylamines such as iodinated ethylamine, and aralkylamine halides such as phenylethylamine iodides.
[0045] Of the target materials that are used when forming a film of an organic-inorganic perovskite by codeposition, examples of the inorganic material constituting M include, but are not limited to, metal halides such as lead iodide.
EXAMPLES
[0046] Hereinafter, the present invention will be explained in further detail by referring to examples etc., but the present invention is not to be construed as being limited by these examples etc.
Comparative Example 1
[0047] A laser deposition apparatus was set up by installing PbI.sub.2 and CH.sub.3NH.sub.3I as targets (to be irradiated by laser beams) inside a vacuum chamber for deposition, so as to irradiate both targets respectively with continuous-wave laser beams having a wavelength of 808 nm.
[0048] After setting the vacuum level inside the vacuum chamber to 10.sup.−5 Pa, the power of the PbI.sub.2-side laser was raised to 1.6 W, the power of the CH.sub.3NH.sub.3I-side laser was raised to 6 W, and organolead perovskite (CH.sub.3NH.sub.3PbI.sub.3) was formed by codeposition onto a glass substrate surface. However, vaporization of the CH.sub.3NH.sub.3I during film formation degraded the vacuum level to 1 Pa. After codeposition, the PbI.sub.2 target was contaminated to a brown color by the spread of CH.sub.3NH.sub.3I. Additionally, the resulting film, in view of XRD analysis and the UV/visible absorption spectrum and the like, could not be considered to be pure organolead perovskite (CH.sub.3NH.sub.3PbI.sub.3), and was a mixed material containing large quantities of unreacted raw material.
Comparative Example 2
[0049] A film of organolead perovskite (CH.sub.3NH.sub.3PbI.sub.3) was formed by codeposition in the same manner as in Comparative Example 1, except that the power of the CH.sub.3NH.sub.3I-side laser was lowered to 2 W. The degradation of the vacuum level due to vaporization of CH.sub.3NH.sub.3I during film formation was suppressed to 10.sup.−2 Pa. However, after codeposition, the PbI.sub.2 target was contaminated to a brown color by the spread of CH.sub.3NH.sub.3I. Additionally, the resulting film, in view of XRD analysis and the UV/visible absorption spectrum and the like, could not be considered to be pure organolead perovskite (CH.sub.3NH.sub.3PbI.sub.3), and was a mixed material containing large quantities of unreacted raw material.
(Example 1) <Duty Ratio Adjustment Example>
[0050] Inside a vacuum chamber for deposition, PbI.sub.2 and CH.sub.3NH.sub.3I were installed as targets, and a crystal oscillator film thickness meter (provided near the path of the evaporation flux for measuring the film thickness of the deposition film, the same applies to crystal oscillator film thickness meters hereafter) was installed in order to measure the evaporation rate of the PbI.sub.2 and the CH.sub.3NH.sub.3I. A laser deposition apparatus was set up so as to irradiate the PbI.sub.2 with a continuous-wave laser beam having a wavelength of 808 nm, and to irradiate the CH.sub.3NH.sub.3I, which is a material having a high vapor pressure, with a pulsed laser beam modulated at 10 Hz and having a wavelength of 808 nm.
[0051] After setting the vacuum level inside the vacuum chamber to 10.sup.−5 Pa, the power of the PbI.sub.2-side laser was raised to 1.6 W, and for the CH.sub.3NH.sub.3I-side laser, the pulse amplitude was set to 17.9 W and the duty ratio was adjusted to 26%, and codeposition was conducted onto a glass substrate surface. At that time, the total evaporation rate for PbI.sub.2 and CH.sub.3NH.sub.3I (the time derivative of the deposition film thickness evolution measured by the crystal oscillator film thickness meter) evolved in a relatively stable manner, without large variations, as shown in the graph in
[0052] After codeposition, the PbI.sub.2 target was observed, but absolutely no contamination of the PbI.sub.2 target due to the spread of CH.sub.3NH.sub.3I was observed. Additionally, the resulting film, in view of XRD analysis and the UV/visible absorption spectrum and the like, was confirmed to be an organolead perovskite (CH.sub.3NH.sub.3PbI.sub.3) with relatively good crystallinity.
(Example 2) <Duty Ratio Adjustment Example 1 Based on Evaporation Rate Measurement>
[0053] A laser deposition apparatus was set up by installing PbI.sub.2 and CH.sub.3NH.sub.3I as targets inside a vacuum chamber for deposition and also installing a crystal oscillator film thickness meter for measuring the evaporation rate of the CH.sub.3NH.sub.3I, so as to irradiate the CH.sub.3NH.sub.3I with a pulsed laser beam modulated at 10 Hz and having a wavelength of 808 nm, while not laser-irradiating the PbI.sub.2.
[0054] After setting the vacuum level inside the vacuum chamber to 10.sup.−5 Pa, deposition was conducted onto the glass substrate surface after setting the CH.sub.3NH.sub.3I-side laser so as to have a pulse amplitude of 17.9 W and adjusting the duty ratio to 40%, 50% and 60%. The evolution of the evaporation rate of CH.sub.3NH.sub.3I in that case is shown in
[0055] After deposition, the PbI.sub.2 target was observed, but absolutely no contamination of the PbI.sub.2 target due to the spread of CH.sub.3NH.sub.3I was observed.
(Example 3) <Duty Ratio Adjustment Example 2 Based on Evaporation Rate Measurement>
[0056] A laser deposition apparatus was set up by installing PbI.sub.2 and CH.sub.3NH.sub.3I as targets and also installing a crystal oscillator film thickness meter for measuring the evaporation rate of the PbI.sub.2 and the CH.sub.3NH.sub.3I inside a vacuum chamber for deposition, so as to irradiate the PbI.sub.2 with a continuous-wave laser beam having a wavelength of 808 nm, and to irradiate the CH.sub.3NH.sub.3I, which is a material having a high vapor pressure, with a pulsed laser beam modulated at 10 Hz and having a wavelength of 808 nm, while observing the PbI.sub.2 and CH.sub.3NH.sub.3I evaporation rates and the vacuum level inside the vacuum chamber.
[0057] After setting the vacuum level inside the vacuum chamber to 10.sup.−5 Pa, the amplitudes of the high-vapor-pressure CH.sub.3NH.sub.3I-side laser pulses were gradually raised until the evaporation rate of the CH.sub.3NH.sub.3I became observable. Upon observing the evaporation rate of CH.sub.3NH.sub.3I, the duty ratio of the laser was gradually raised to set the evaporation rate to a target value of 0.5 Å/s. Next, the power of the PbI.sub.2-side laser was raised, the PbI.sub.2 was evaporated, the evaporation rate (the total evaporation rate for PbI.sub.2 and CH.sub.3NH.sub.3I), while being observed with the crystal oscillator film thickness meter, was raised to the target value of 1.0 Å/s for codeposition. The CH.sub.3NH.sub.3I-side laser was set so as to have a pulse amplitude of 17.9 W and the duty ratio was adjusted to 36%. Thereafter, the PbI.sub.2-side laser power was raised to 0.7 W and codeposition was started. In order to maintain the evaporation rate, the duty ratio of the CH.sub.3NH.sub.3I-side laser pulses was adjusted between 36% and 32% while observing the film thickness meter. During codeposition, the film thickness meter was observed until the deposited film thickness reached a target film thickness (100 nm), and the evaporation rate (1.0 Å/s) for codeposition was maintained by adjusting the duty ratio while estimating the evaporation rate of CH.sub.3NH.sub.3I.
[0058]
(Example 4) <Duty Ratio Adjustment Example Based on Vacuum Level Measurement>
[0059] Using a laser deposition apparatus that was set up in the same manner as Example 3, after setting the vacuum level inside the vacuum chamber to 10.sup.−5 Pa, the power of the PbI.sub.2-side laser was raised, the PbI.sub.2 was evaporated, and the PbI.sub.2 evaporation rate, while being observed with the crystal oscillator film thickness meter, was raised to a target value (0.3 Å/s). Meanwhile, as for the laser for evaporating CH.sub.3NH.sub.3I, which has a high vapor pressure, the amplitudes of the laser pulses were gradually raised while observing the vacuum level of the vacuum chamber, and the vacuum level was made to approach a target value (1.0×10.sup.−3 Pa, 5.0×10.sup.−3 Pa or 8.0×10.sup.−3 Pa). When the vacuum level exceeded the target value, the duty ratio of the laser was adjusted so as to set the vacuum level to the target value, by means of an operation such as lowering the duty ratio of the laser used for evaporating CH.sub.3NH.sub.3I. Next, the PbI.sub.2-side laser power was raised to 0.5 W, after which the CH.sub.3NH.sub.3I-side laser pulse amplitude was set to 17.9 W and the duty ratio was adjusted to 41%, and codeposition was started. During codeposition, the duty ratio was adjusted within the range of 41% to 39%, while observing the vacuum meter, so as to keep the vacuum level to within a range of 90%/o to 110% of the target value, until the deposition film thickness reached a target film thickness (100 nm). As a result, the total evaporation rate of the inorganic material PbI.sub.2 and the organic material CH.sub.3NH.sub.3I during codeposition was maintained at approximately 0.6 Å/s.
[0060] The time evolution of the evaporation rate when the target value of the vacuum level was 1.0×10.sup.−3 Pa is shown in
[0061] The formation of an organolead perovskite film is possible by either a method wherein the duty ratio is adjusted based on the measured evaporation rate as in Example 3, or by a method wherein the duty ratio is adjusted based on the measured vacuum level in the vacuum chamber as in Example 4, but the method wherein the duty ratio is adjusted based on the measured vacuum level in the vacuum chamber provided a perovskite film of higher uniformity and provided higher photoelectric conversion performance.
INDUSTRIAL APPLICABILITY
[0062] According to the laser deposition method and the laser deposition apparatus of the present invention, it is possible to effectively and stably form deposition films of various organic materials, while preventing problems such as contamination due to vaporization of the organic material or the film formation rate becoming uncontrollable. Therefore, the invention can be applied not only to the deposition of thin films of just organic materials, but also to the codeposition of various types of organic-inorganic composites, such as organic-inorganic composite perovskites for use in solar cells, EL elements, or the like.