CN113550005A

CN113550005A - Transverse region melting and recrystallization device for perovskite polycrystalline thin film

Info

Publication number: CN113550005A
Application number: CN202010375333.8A
Authority: CN
Inventors: 张楚; 郑小鹿
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-04-26
Filing date: 2020-04-26
Publication date: 2021-10-26

Abstract

The invention discloses a device for recrystallizing an organic-inorganic metal halide perovskite polycrystalline thin film material, and particularly relates to transverse region melting recrystallization, which is beneficial to reducing gaps among crystal domains, eliminating interfaces among the crystal domains and enlarging the crystal domains. The device comprises a radiation source of a light radiation diode (LED) or a Laser Diode (LD), a focusing unit and a linear leading-in device. The invention is suitable for the requirements of perovskite quasi-single crystals with larger area or polycrystalline films with larger crystal domains, such as photovoltaic films, LED display luminescent films, image detector films, x-ray image detector films and the like.

Description

Transverse region melting and recrystallization device for perovskite polycrystalline thin film

The technical field is as follows:

the invention relates to the manufacture of photovoltaic polycrystalline thin films, to semiconductor light sources for the thermal treatment of materials, and to perovskite semiconductor photovoltaic materials.

Background art:

polycrystalline thin film solar cells based on organic-inorganic metal halide perovskites prepared by solution crystal growth have rapidly progressed in the last decade, but before they can replace solar cells on crystalline silicon wafers, there are still some serious problems to be solved, such as stability problems and kickback problems. One of the sources of the problems is that the crystal domain of the metal halide perovskite polycrystalline thin film obtained by the current preparation method is small, the size of the metal halide perovskite polycrystalline thin film is related to various parameters and processes of the process, and the size of the metal halide perovskite polycrystalline thin film is generally below micrometers; a large number of gaps exist among the crystal domains, subcrystal boundaries exist in the crystal domains, and a large number of defects and impurities such as vacancies, dangling bonds, dislocations and the like exist in the interfaces of the crystal domains; the organic cations in the perovskite crystal lattice on the interface and the sub-interface are easy to move out and translocate in the aging process; the size of the domains also limits the carrier diffusion length to the order of microns, which is far from the order of hundreds of microns required for devices.

Historically, similar domain problems have existed for amorphous silicon and polysilicon thin film materials. A lateral zone melting recrystallization technique (ZMR) was developed since the 1980 s for the preparation of crystalline silicon films (SOI) on silicon dioxide layers. The method carries out transverse area melting on the amorphous silicon or polycrystalline silicon thin film on the silicon-based silicon dioxide thin layer, and a monocrystalline silicon thin film, a quasi-monocrystalline silicon thin film or a polycrystalline silicon thin film is recrystallized according to the condition that whether a seed crystal is provided or not. U.S. patent No. 4371421 (patent No. 4371421) in 1983, U.S. patent No. 5453153 (Zone-melting recrystallization process) in 1995, and chinese patent No. CN200980108990.8 (process for regional melt recrystallization for inorganic films) in 2011 describe techniques and apparatuses for Lateral region melt recrystallization, but they are limited to silicon-based semiconductor thin films.

Chinese patent application No. 201911333356.6, 2019, "apparatus and method for transverse zone melt recrystallization of a perovskite thin film" describes a transverse zone melt recrystallization technique and apparatus for polycrystalline thin films of organic-inorganic metal halide perovskites. The method limits the high temperature required by remelting to be near the liquid-solid interface which is pushed by transverse growth, avoids the influence of the high temperature on the whole film for too long time, and has a liquid-solid interface temperature gradient pushing accurate controllable mode similar to crystal epitaxial growth. Aiming at the problem that the steam pressure of component elements or precursors in the multi-element polycrystalline film at the same temperature is far from each other, so that the elements or precursors with high steam pressure values are easy to become an escape phase and lose the escape phase on crystal lattices, a method of supplementing precursor steam in the environment atmosphere of remelting crystallization is adopted. In the example of the apparatus, the polycrystalline film sample is located on a fixed heated platform within the vessel, and the transverse advancement of the focused region of radiation is achieved by a scanning mechanism outside the vessel. The following disadvantages and shortcomings exist in this device:

a large area of transparent glass or quartz glass with stringent optical quality requirements needs to be arranged on the top of the container; the long focal length of the radiation source is required, and the light emitting device is required to have a small divergence angle, which makes it difficult to use a Light Emitting Diode (LED) as a light source of the radiation source. However, the electro-optic energy conversion rate of the LED is higher than that of a semiconductor Laser (LD), so that the price and cost are more advantageous, and if the short focusing length can be adopted to meet the radiation focusing requirement, the LED is preferable as a radiation source.

The invention content is as follows:

the present invention is directed to an apparatus for melt recrystallization of a lateral region of a polycrystalline thin film, which overcomes the above-mentioned disadvantages or drawbacks of the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a transverse region melting and recrystallization device for a perovskite polycrystalline film comprises a container, a radiation source and a heating platform, wherein strip-shaped radiation generated by the radiation source fixed on the container is focused on a film sample on the heating platform in the container, the container and the heating platform are connected through a linear leading-in device to push and pull the heating platform, and the transverse region melting and recrystallization device further comprises a precursor generator and a precursor gas sensor which are communicated with a gas circuit of the container.

According to the scheme, the radiation source is a strip radiation source adopting an LED or LD device, and comprises a ceramic metal substrate connected with a radiation shell radiator, a plurality of bare chips or packaging devices of the LED or LD, and a strip-shaped convergence optical assembly, wherein the bare chips or the packaging devices are uniformly distributed on the substrate in a strip shape, and the strip-shaped convergence optical assembly receives radiation and focuses the radiation into strip-shaped radiation at an emergent end.

According to the scheme, the strip-shaped converging optical assembly is composed of a plurality of compound lenses and a cylindrical lens, the compound lenses receive radiation of a single LED or LD device and emit the radiation to the cylindrical lens which is transversely placed and focuses the radiation into a strip shape.

According to the scheme, the strip-shaped converging optical component is a strip-shaped light guide wedge, the large end and the small end of the wedge body are respectively formed curved surfaces, the large end curved surface receives radiation of an LED or LD device, the small end curved surface focuses the radiation into a strip shape, and the side surface generates full emission.

According to the scheme, the strip-shaped convergence optical assembly is composed of a plurality of light guide columns and a cylindrical lens, wherein the curved surface at one end of each light guide column receives the radiation of a single LED or LD device, and the curved surface at the other end of each light guide column emits the radiation to the cylindrical lens which is transversely arranged and focuses the radiation into a strip shape.

According to the scheme, the precursor generator or the precursor gas sensor container is arranged inside the container, or is connected with another container arranged outside the container through a gas pipeline.

According to the scheme, the linear leading-in device comprises a through type axial direct current movement stepping motor containing a hollow threaded shaft, a screw rod and a corrugated pipe, wherein the screw rod penetrates through the shaft hole of the hollow threaded shaft and the corrugated pipe to drive the heating platform to do linear movement.

In the selection of the radiation source in the above scheme, factors such as the heating mechanism and the wavelength range of the radiation, the size of the radiation focusing region, the incident energy density, the divergence angle of the radiation source, the cost and the service life need to be comprehensively considered. The examples of the present invention employ LED and LD devices, and the specific analysis is as follows:

heating mechanism and wavelength range. It is known that the absorption band wavelength of methylamine triiodide starts from about 800 nm (1.55eV) to the short wavelength direction, the absorption band wavelength of the precursor lead diiodide starts from about 550 nm (2.4eV) to the short wavelength direction, and that another precursor, methylamine iodide, is a wide forbidden band, has an absorption wavelength higher than uv, and is transparent to commonly used radiation sources. Radiation in the far infrared to infrared bands will be less absorbed in the film sample because the heating mechanism on the film sample due to radiation results from relaxation after interband absorption. 405 nm for blue-violet light, 450 nm for blue light, 520 nm or 532 nm for green light LD devices and similar wavelength range LED devices are all alternatives.

The size of the radiation focal zone and the incident energy density. The process of transverse zone melting and recrystallization is most dependent on the transverse temperature gradient. This in turn depends on the radiation intensity, the scanning speed, the width of the focal zone in the scanning direction and the heating temperature of the sample electric heater 13. Taking a single LD with an output radiation power of 5 watts as an example, if the focal region has a rectangular area, the long side is 5 mm, and the short side is 0.4 mm, the power density is 250 watts/square centimeter; if the scanning speed along the short side direction is 10 mm/s, the action time of the laser in the focusing area is 40 milliseconds, the total incident energy density is 10 joules/square centimeter, and the energy absorbed in the scanned focusing area is 0.2 joules. In practice, a coordinated adaptation of the above parameters is required so that the incident energy density ranges from 100 mJ/cm to 50J/cm. The length-width ratio of the focusing region is better, and under the condition that other conditions such as power density and the like are not changed, the incident energy density is reduced, and the precursor gasification loss is also reduced.

The LD has particular advantages in the laser processing, particularly engraving and cutting fields, due to its small divergence angle, ease of convergence, and ease of achieving high power density over a small area, and is also widely used in other surface processing and handling fields such as cladding, welding, and annealing, although the spot size or line width required in these fields is not critical and does not need to approach the LD focus limit. In the invention, the transverse zone melting recrystallization has focusing requirements on a radiation source, and the LED is not easy to focus compared with LD; the divergence angle of the LED is larger than that of the LD, and the LED is difficult to be completely collected by the optical lens; however, the electro-optical energy conversion efficiency of the LED is higher than that of the LD. Both are short and long, and are used in various embodiments of the radiation source of the present invention.

The invention has the advantages that:

1. the device of the invention is suitable for large-scale production with low cost, and is suitable for the requirements of perovskite quasi-single crystals with large area or polycrystal with large crystal domain, such as photovoltaic films, LED display luminescent films, image detector films, x-ray image detector films and the like.

2. The perovskite quasi-single crystal film or the polycrystalline film with larger crystal domains prepared by the invention reduces the gaps among the crystal domains, reduces the sub-interfaces in the crystal domains, reduces the interfaces among the crystal domains, and improves the stability problem and the flyback problem of the existing perovskite polycrystalline film.

3. The radiation source adopted by the device is a high-power LED and LD device, and forms strip radiation, so that the device has the advantages of high electro-optical efficiency, low cost and long service life.

4. The radiation outlet of the radiation source adopted by the device is connected into the growth cavity, and radiation is directly focused on the polycrystalline film, so that atmosphere isolation glass is omitted, the stability of process conditions is improved, and radiation loss is reduced.

5. The linear leading-in device adopted by the device ensures the process atmosphere environment and simultaneously realizes the transverse movement of the sample.

Description of the drawings:

fig. 1 is a cross-sectional side view of an apparatus according to a first embodiment of the invention.

FIG. 2 is a cross-sectional view of a strip radiation source used in an embodiment of the present invention, the left side view being a long side cross-sectional side view and the right side view being a short side cross-sectional side view.

FIG. 3 is a cross-sectional view of a strip radiation source according to a second embodiment of the present invention, the left side view being a long side cross-sectional side view and the right side view being a short side cross-sectional side view.

FIG. 4 is a cross-sectional view of a strip radiation source used in a third embodiment of the present invention, the left side view being a long side cross-sectional side view and the right side view being a short side cross-sectional side view.

The specific implementation mode is as follows:

the following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

The precursor thin film or polycrystalline thin film used for implementing the melting recrystallization in the transverse region in the following embodiments may be a perovskite thin film of methylamine lead triiodide prepared by a one-step spin coating method, or may be a perovskite polycrystalline or amorphous thin film prepared by other different methods such as a two-step method, a chemical deposition method, a physical deposition method, or a hot casting method.

Examples one to three examples the atmosphere control and growth environment for the thin films used is shown in fig. 1 at 10, where the strip-shaped radiation source in the different examples is 30 in fig. 2, 40 in fig. 3 or 50 in fig. 4, which is hermetically mounted in the opening at the upper side of the chamber 11, the outgoing strip-shaped radiation being focused on the surface of the sample 12.

The sealed rectangular container 11 is made of stainless steel plate, a movable sealing door (not shown) capable of loading and unloading the sample 12 is opened on one side of the container, the vacuum degree in the container 11 reaches 10KPa, and the pressure reaches 0.3 MPa. The perovskite polycrystalline thin film sample 12 is placed on a heating stage 13, and the bottom of the heating stage 13 is moved on a pair of oil-free sliding rails (not shown), the fixed portions of which are mounted on a fixed base plate 15 of a ceramic insulating material. The heating platform 13 is made of block-shaped cast copper or cast aluminum, the surface of the heating platform is polished, a water cooling pipeline (not shown) and an electric heating rod 14 are arranged in the heating platform, the temperature is controlled by a microprocessor, the temperature of the perovskite material of methylamine triiodide can be set to 300 ℃ from room temperature, the control precision is 0.5 ℃, the heating rate can reach 20 ℃/min, and the cooling rate can reach 10 ℃/min.

The heating platform 13 obtains pulling and pushing power to realize translation through a vacuum linear guide device which is composed of a through type axial direct current motion stepping motor 17 containing a hollow threaded shaft, a screw 16 and a corrugated pipe 18. The two ends of the corrugated pipe contain sealing flanges, one end of the corrugated pipe is fixedly connected with the container 11, and the other end of the corrugated pipe is fixedly connected with the heating platform 13 in a heat insulation way. The screw 16 passes through one end of the bellows 18 and is centrally fixed to the sealing flange at the other end. The stepping motor 17 is a 57-type through linear screw stepping motor, and the lead of a hollow threaded shaft is 4 mm. The translation speed of the heating stage 13 is determined according to the process conditions such as the radiant energy density, the material of the sample, the base temperature of the heating stage 13, and the like, and the rotation speed of the motor 17 is controlled and adjusted so that the translation speed is in the range of 1 mm/s to 30 mm/s.

The precursor generator 21 is arranged in the sealed container 11, and the interior of the generator contains an electric heater 22 made of an electric heating wire, the material of the electric heater is cast copper or cast aluminum blocks, and the surface of the electric heater is polished. The precursor powder 20 is placed in the cavity of the precursor generator 21, the heating temperature is controlled by a separate microprocessor, such as methyl amine iodide, which can reach 300 ℃, the control precision is 0.5 ℃, the heating rate can reach 20 ℃/min, and the cooling rate can reach 10 ℃/min. The foot pad is made of heat-insulating ceramic material. Two gas valves (not shown) mounted on the outside of the side of the container 11 are used for connecting pipes to external gas circuits, so as to realize the intake of nitrogen and hydrogen and the extraction of gas in the cavity. A pressure sensor 23 and a precursor gas partial pressure sensor 24 mounted on the top of the interior of the container 11 for monitoring the amount of precursor produced and feeding back to the microprocessor.

Suitable positions on the top or sides of the container 11 allow the opening of optical windows (not shown) for observing and monitoring the growth process of the film, and also allow the installation of instruments for contactless on-line detection.

The first embodiment is as follows:

example one illustrative embodiment of a strip radiation source is shown in schematic form at 30 in fig. 1, and further shown at 30 in fig. 2, with the left side view being a side view in cross-section of the long side and the right side view being a side view in cross-section of the short side. The cavity 31 of the radiation source is made of copper or aluminum, the top of the cavity is designed to be a heat dissipation strip, and a liquid refrigeration pipeline and a connecting port 33 are arranged inside the cavity. The ceramic metal substrate 32 is a strip-shaped three-layer structure material: a copper or aluminum metal substrate is in close contact with the cavity 31, a high thermal conductivity insulating ceramic sheet is in the middle, and a plurality of LED or LD devices 34 are mounted on the patterned copper-based circuit. The aspheric lenses 35 of the one-dimensional array correspond to the devices 34 one-to-one, and the aspheric lenses 35 may also be a combined lens unit including a micro fly-eye. The numerical aperture of 35 matches the divergence angle of device 34. Cylindrical lens 37 further focuses the radiation into a strip shape. The convergence unit vessel 36 combines 32, 34, 35 and 37 into a fixed sealed whole, and the space 38 inside 36 is filled with inert shielding gas. If the device 34 is a packaged non-bare chip, the container 36 may relieve the hermetic seal requirement.

Example two:

example two the atmosphere control environment for the film used was constructed as shown at 10 in figure 1 except that the strip radiation source 30 was replaced with 40. Example two a schematic diagram of a strip radiation source is further illustrated at 40 in figure 3, the left side view being a side view in cross-section of the long side and the right side view being a side view in cross-section of the short side. The cavity 41 of the radiation source is made of copper or aluminum, the top of the cavity is designed to be a heat dissipation strip, and a liquid refrigeration pipeline and a connecting port 43 are arranged inside the cavity. The ceramic metal substrate 42 is a strip-shaped three-layer structure material: a copper or aluminum metal substrate is in close contact with the cavity 41, a high thermal conductivity insulating ceramic sheet is in the middle, and a plurality of LED or LD devices 44 are mounted on the patterned copper-based circuit. The upper part of the light guide row 45 is a one-dimensional array of a plurality of curved surfaces, each of which corresponds to a device 44 one by one, and the numerical aperture is matched with the divergence angle of the device 44. The lower part of the light guide row 45 is a cylindrical curved surface, focusing the radiation into a strip shape. The convergence cell container 46 combines 42, 44 and 45 into a fixed sealed unitary body, with the space 48 inside the container 46 filled with an inert shielding gas. If the device 44 is a packaged non-bare chip, the container 46 may relieve the hermetic seal requirement.

Example three:

example three the atmosphere control environment for the film used was constructed as shown at 10 in figure 1 except that the strip radiation source 30 was replaced with 50. Third embodiment the schematic diagram of a strip radiation source used is further illustrated in fig. 4 at 50, the left side view being a side view in cross-section of the long side and the right side view being a side view in cross-section of the short side. The cavity 51 of the radiation source is made of copper or aluminum, the top of the cavity is designed to be a heat dissipation strip, and a liquid refrigeration pipeline and a connecting port 53 are arranged inside the cavity. The ceramic metal substrate 52 is a strip-shaped three-layer structure material: a copper or aluminum metal substrate is in close contact with the cavity 51 with a high thermal conductivity insulating ceramic sheet in the middle, and a patterned copper-based circuit is mounted with a plurality of LED or LD devices 54. The upper end of the light guide column 55 is an aspheric curved surface, the light guide columns 55 correspond to the devices 54 one by one, and the numerical aperture of each light guide column is matched with the divergence angle of the device 54. The lower end of the light guide column 55 is an aspheric curved surface, and the output of the plurality of light guide columns is coupled with a cylindrical lens of a non-circular surface to focus the radiation into a strip shape. The convergence cell vessel 56 combines 52, 54, 55 and 57 into a fixed sealed unitary body, with the space 58 inside the vessel 56 filled with an inert shielding gas. If the device 54 is a packaged non-bare chip, the container 56 may relieve the hermetic seal requirement.

The

devices

34, 44 and 54 in the above embodiments all adopt Cree LED chips, model XP-E, wavelength 420-. If each radiation is focused at a stripe interval of 2 mm x0.2 mm, the radiation power density is 450 watts per square centimeter, regardless of optical convergence losses. In the examples, 120 pieces (only 12 pieces of which are shown in 30, 40 and 50 of the schematic drawings) were used at a pitch of 2 mm, so that the width of one transverse zone-melting was 240 mm. The movement speed of the stage was set at 10 mm/sec, the 0.2 mm bar-shaped melting zone experienced 0.02 sec of radiation, the incident energy density was 4.5 joules/cm, disregarding the optical convergence losses. The numerical aperture of the front lens or front curve is selected to be 0.54, which corresponds to a full angle of 56 degrees. However, the chip has a total radiation angle of 120 degrees and has a partial optical loss.

The

devices

34, 44 and 54 in the above embodiments can also be made of Nichia's multi-mode LD tube, model NDB7Z75E, wavelength 462 and 472 nm, the tube diameter is 9 mm, the radiation power is 5W at 3.5A current and 4.1V voltage, and the electro-optic efficiency is about 35%. If each radiation is focused at a strip interval of 10 mm x0.2 mm, the radiation power density is 250 watts per square centimeter, regardless of optical convergence losses. In the example, 24 (only 12 of which are shown in 30, 40 and 50 of the schematic drawings) are used at a pitch of 10 mm, so that the width of one transverse zone-melting is 240 mm. The movement speed of the stage was set at 10 mm/sec, the 0.2 mm bar-shaped melting zone experienced 0.02 sec of radiation, regardless of optical convergence losses, and the incident energy density was 2.25 joules/cm. The numerical aperture of the front lens or front curve is selected to be 0.54, which corresponds to a full angle of 56 degrees. The total angle of radiation of the tube, 10.5 and 46 degrees in the two perpendicular directions, respectively, can be fully received by the strip concentrating optical assembly in the embodiments described above.

The radiation exit focal length of each condensing unit in the above embodiments is in the range of 8 mm to 30 mm.

Claims

1. The transverse region melting recrystallization device for the perovskite polycrystalline thin film comprises a container, a radiation source and a heating platform, and is characterized in that strip-shaped radiation generated by the radiation source fixed on the container is focused on a thin film sample on the heating platform in the container, the container and the heating platform are connected through a linear guide device to push and pull the heating platform, and the transverse region melting recrystallization device further comprises a precursor generator and a precursor gas sensor which are communicated with a gas circuit of the container.

2. An apparatus for transverse zone melt recrystallization of perovskite polycrystalline thin film as defined in claim 1 wherein the radiation source is a bar-shaped radiation source employing a Light Emitting Diode (LED) or a Laser Diode (LD), comprising a ceramic metal substrate associated with a radiation housing heat sink, a plurality of bare chips or packaged devices of LEDs or LDs mounted in a uniform distribution in a bar shape on the substrate, and a bar-shaped converging optical assembly for receiving the radiation and focusing the radiation in the bar shape at an exit end.

3. An apparatus for melt recrystallization of transverse regions of a perovskite polycrystalline thin film as defined in claim 1 or 2 wherein the bar-shaped converging optical element is comprised of a plurality of compound lenses and a cylindrical lens, the compound lenses receiving radiation from individual said LED or LD devices and emitting to the transversely disposed cylindrical lens which focuses the radiation into a bar shape.

4. An apparatus for transverse zone melt recrystallization of a perovskite polycrystalline thin film as defined in claim 1 or 2 wherein the bar-shaped converging optical element is a bar-shaped light guiding wedge having a large end and a small end each formed into a curved surface, the large end curved surface receiving the radiation from the LED or LD device, and the small end curved surface focusing the radiation into a bar shape and producing total emission laterally.

5. An apparatus for melt recrystallization of transverse regions of a perovskite polycrystalline thin film as defined in claim 1 or 2 wherein the bar-shaped converging optical element is comprised of a plurality of light guiding bars having one curved surface receiving the radiation from a single said LED or LD device and the other curved surface exiting to the transversely disposed cylindrical lens which focuses the radiation into a bar shape.

6. The apparatus for melt recrystallization of the transverse region of a perovskite polycrystalline thin film according to claim 1, wherein the precursor generator or precursor gas sensor vessel is disposed inside the vessel, or is connected to another vessel disposed outside the vessel through a gas conduit.

7. The apparatus for melting and recrystallizing a transverse region of a perovskite polycrystalline thin film according to claim 1, wherein the linear guide means comprises a through axial dc motion stepping motor having a hollow screw shaft, a screw rod and a bellows, the screw rod passing through the shaft hole of the hollow screw shaft and the bellows to drive the heating stage to move linearly.