Perovskite battery organic precursor evaporation equipment and evaporation method

Abstract

The invention relates to a perovskite cell organic precursor evaporation device and an evaporation method.The evaporation device comprises a deposition cavity, an evaporation cavity and a transmission pipeline connecting the evaporation cavity and the upper center of the deposition cavity, the transmission pipeline is provided with a porous spraying head at an outlet of the deposition cavity, and the bottom of the porous spraying head is a net plate facing the upper surface of a substrate; the distance between the screen plate and the substrate is 1 / 3-1 / 2 of the diameter of the deposition cavity and ranges from 5 cm to 20 cm, and the diameter of the screen plate is 70%-90% of the diameter of the deposition cavity. The evaporation method comprises the steps of evaporation, carrier gas conveying and deposition. Through the low-temperature carrier gas evaporation method, the decomposition risk of the organic precursor under the high vacuum condition is remarkably reduced, and the problem of pressure fluctuation of the deposition cavity is relieved. The evaporation cavity and the deposition cavity have proper pressure difference, formed sprayed organic vapor molecules are high in kinetic energy, a columnar spraying form with high directionality is formed under the assistance of natural gravity, the compactness of an organic film is enhanced, and the material utilization rate is high.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and particularly to an organic precursor evaporation device and an evaporation method for perovskite solar cells. Background Art

[0002] At present, perovskite solar cells are mostly prepared by solution methods, but there are problems of uneven film thickness and poor repeatability. Vacuum evaporation technology has received attention due to its high uniformity and suitability for large-area preparation. However, when using organic precursors (such as FAI, MAI, and FABr), high temperatures are likely to cause decomposition, which in turn leads to a sharp rise in chamber pressure, deposition stoichiometry deviation, and a decline in film quality. Existing literature shows that by using an external evaporation chamber and carrier gas-assisted transport, effective sublimation of the precursor can be achieved at a lower temperature, thereby avoiding or reducing the decomposition phenomenon and improving the pressure fluctuation during deposition. In addition, in addition to FAI, MAI and FABr are commonly used organic precursors in perovskites, and their reasonable control plays an important role in the bandgap regulation, stability, and device performance of the final perovskite film. In the prior art, there is still room for optimization of the evaporation process parameters of the precursor, and there is an urgent need for an advanced process method that comprehensively considers the characteristics of various precursors, pressure control, and carrier gas transport.

[0003] Conventional evaporation is bottom-up evaporation, that is, the heating evaporation source is at the bottom and the substrate is at the top. Since organic gases have a relatively large molecular weight and a diffuse distribution, their upward kinetic energy is not strong, resulting in low deposition efficiency. At the same time, the evaporation source and the substrate are in the same chamber with a unified pressure, and sufficient jet kinetic energy cannot be formed, which also leads to low deposition efficiency and a very low density of the deposited film, and the film is not dense enough.

[0004] An evaporation device for perovskite thin films, its use method and application disclosed in Chinese Patent CN107779840A have a structure in which the evaporation system is externally disposed outside the deposition system. The evaporation system generates coating vapor, which is sent into the evaporation system through a vapor channel. The deposition substrate is vertically placed on a deposition bracket in the deposition chamber and is coated. A heating device is provided on the side wall of the deposition chamber to heat the deposition chamber. The problems existing here are: 1. The coating vapor needs to diffuse in the entire space of the deposition chamber before coating. Since the air flow velocity in the space is different, the deposition rate is uneven.

[0005] 2. The heating device needs to rely on the convection of the coating vapor to heat the coating vapor. Since the diffused air flow state is uneven, the uniformity of heat is also relatively poor, which will also make the coating quality uneven.

[0006] 3. When the coating vapor adheres to the deposition substrate by diffusion, a large amount of coating vapor will also adhere to the inner wall of the deposition chamber, resulting in low material utilization.

[0007] 4. When coating, the organic gas diffuses to the substrate by free diffusion. The deposition kinetic energy of organic molecules is weak, and a dense organic film layer cannot be formed.

[0008] 5. The molecular weight of the organic vapor is relatively large, and it is greatly affected by gravity. Therefore, its distribution in the cavity is that the concentration at the bottom is relatively large and the concentration at the top is relatively low. When coating, the coating rates at the upper and lower positions are inconsistent, and the coating thickness is uneven up and down.

[0009] Therefore, it is necessary to improve the equipment structure and coating method to solve the above problems. Summary of the Invention

[0010] The main object of the present invention is to provide an organic precursor evaporation coating equipment for perovskite batteries, which can make the coating flow rate and temperature of the perovskite organic precursor more uniform.

[0011] The present invention realizes the above object through the following technical solutions: an organic precursor evaporation coating equipment for perovskite batteries, including a deposition chamber, an evaporation chamber, and a transmission pipeline connecting the upper center of the evaporation chamber and the deposition chamber. A carrier gas diversion pipe is provided on the transmission pipeline, a heating mechanism is provided in the transmission pipeline, a carrier table assembly for horizontally placing a substrate is provided in the middle of the deposition chamber, a porous spray head is provided at the outlet of the transmission pipeline in the deposition chamber, the bottom of the porous spray head is a mesh plate facing the upper surface of the substrate, the distance from the mesh plate to the substrate is 1 / 3 - 1 / 2 of the diameter of the deposition chamber and is between 5 cm and 20 cm, and the diameter of the mesh plate is 70% - 90% of the diameter of the deposition chamber.

[0012] Specifically, the carrier table assembly includes a tabletop at the upper part, a cooling chamber inside the tabletop, and a rotating mechanism for driving the tabletop to rotate around a vertical rotation axis, and the vertical rotation axis is collinear with the vertical central axis of the mesh plate.

[0013] Specifically, a heat insulation layer is provided on the outer wall of the deposition chamber.

[0014] Specifically, a crucible for placing an organic precursor, a heating device for heating the organic precursor, and a pressure sensor for measuring the internal pressure of the evaporation chamber are provided in the evaporation chamber.

[0015] Further, the heating device includes a plasma generator located above the crucible and a pulse heater located below the crucible. A base for raising the crucible is provided in the evaporation chamber, and the pulse heater does not contact the base.

[0016] Further, the crucible is a porous tungsten crucible.

[0017] Another main object of the present invention is to provide a coating method for an organic precursor of a perovskite battery.

[0018] The present invention achieves the above object through the following technical solutions: A method for evaporating an organic precursor of a perovskite battery, which is completed by using the evaporation equipment, and the steps include: S1. Evaporation: Place the organic precursor in a crucible, and perform low-temperature sublimation and molecular cluster depolymerization on the organic precursor through the heating device. The pressure in the evaporation chamber is maintained at 10 -3 ~10 -2 Pa to generate precursor vapor; S2. Carrier gas transportation: Using nitrogen or an inert gas as the carrier gas, send it into the transfer pipeline through the carrier gas guide pipe to form a negative pressure, and suck the precursor vapor into the deposition chamber. The precursor vapor accumulates in the porous spray head, and then uniformly passes through the mesh holes on the mesh plate and sprays onto the substrate from top to bottom; S3. Deposition: The substrate is pre-fixed above the table, and the rotation mechanism controls the substrate to rotate around the vertical rotation axis. The pressure in the deposition chamber is maintained at 10 -5 ~10 -4 Pa. The substrate is kept in a low-temperature state by the refrigerant in the cooling chamber, so that the precursor vapor sublimates on the upper surface of the substrate.

[0019] Specifically, the flow rate of the carrier gas is 5 - 50 sccm, the heating mechanism heats the precursor vapor to 100 - 120 °C, and the inner diameter of the transfer pipeline is 5 - 10 mm.

[0020] Specifically, the temperature of the refrigerant is 10 - 50 °C, and the deposition chamber is a cylindrical vacuum chamber with an inner diameter of 30 - 50 cm.

[0021] Specifically, the power of the plasma generator is 10 - 30 W, the power of the pulse heater is 50 - 100 W, and the pulse width is 0.2 - 0.5 s.

[0022] The beneficial effects of the technical solution of the present invention are: 1. The present invention combines an external evaporation chamber, low-temperature pulse heating, plasma assistance, and carrier gas transportation in a low-temperature carrier gas evaporation method, significantly reducing the decomposition risk of FAI and other organic precursors (MAI, FABr) under high vacuum conditions, and alleviating the problem of deposition chamber pressure fluctuations caused by precursor sublimation.

[0023] 2. The evaporation chamber and the deposition chamber have an appropriate pressure difference, the formed jet organic vapor molecules have strong kinetic energy, and with the assistance of natural gravity, a columnar jet morphology with strong directivity is formed, enhancing the compactness of the organic film and the material utilization rate. Brief Description of the Drawings

[0024] Figure 1 Stereogram of the organic precursor evaporation equipment for perovskite batteries in the embodiment; Figure 2 Sectional view of the deposition chamber and its internal parts; Figure 3 Sectional view of the evaporation chamber and its internal parts.

[0025] The numbers in the figure indicate: 1 - Deposition chamber, 11 - Thermal insulation layer; 2 - Evaporation chamber, 21 - Crucible, 22a - Plasma generator, 22b - Pulse heater, 23 - Pressure sensor, 24 - Base; 3 - Transfer pipeline, 31 - Carrier gas diversion pipe, 32 - Heating mechanism, 33 - Porous spray head, 331 - Mesh plate; 4 - Carrier stage assembly, 41 - Stage surface, 42 - Cooling chamber, 43 - Rotation mechanism. Specific implementation mode

[0026] The present invention will be further described in detail below with reference to specific embodiments.

[0027] Embodiment: As Figure 1 and Figure 2 shown, an organic precursor evaporation equipment for perovskite batteries of the present invention includes a deposition chamber 1, an evaporation chamber 2, and a transfer pipeline 3 connecting the upper center of the evaporation chamber 2 and the deposition chamber 1. A carrier gas diversion pipe 31 is provided on the transfer pipeline 3, a heating mechanism 32 is provided inside the transfer pipeline 3, a carrier stage assembly 4 for horizontally placing a substrate is provided in the middle of the deposition chamber 1, a porous spray head 33 is provided at the outlet of the transfer pipeline 3 in the deposition chamber 1, the bottom of the porous spray head 33 is a mesh plate 331 facing the upper surface of the substrate, and the distance from the mesh plate 331 to the substrate is 1 / 3 - 1 / 2 of the diameter of the deposition chamber 1 and is between 5 cm and 20 cm.

[0028] The evaporation chamber 2 adopts an independent cavity structure externally placed outside the deposition chamber 1, with a volume of 0.5 - 1 L, which is used to evaporate the organic precursor into precursor vapor. The deposition chamber 1 adopts a cylindrical vacuum chamber with a diameter of 30 - 50 cm. The substrate is fixed on the stage assembly 4, and a refrigerant (temperature 10 - 50 °C) is passed through the cooling chamber 42 to control the sublimation of the precursor on the substrate. Since the evaporation chamber 2 and the deposition chamber 1 are separated, a certain pressure difference can be maintained between the two, which is conducive to forming an effective jet from top to bottom. The jet kinetic energy of the precursor vapor is strong, and it has strong directivity under the auxiliary action of gravity, so a perfect columnar jet form can be formed, the compactness of the organic film is enhanced, and the material utilization rate is high. The carrier gas is only a carrier for transporting the organic precursor, providing a transfer flow rate (5 - 50 sccm) for it. The composition of the carrier gas cannot react with the deposit, nor can it enter the deposit as an impurity. Therefore, generally high-purity nitrogen or inert gas (such as argon) is used as the carrier gas, and the flow rate of the carrier gas can be controlled by a mass flow controller and introduced into the deposition chamber 1. There needs to be enough height space between the mesh plate 331 and the substrate. If it is too small, the air flow will be blocked by the mesh holes, resulting in the jet air flow being distributed in the shape of the mesh plate holes, and the air flow distribution is not uniform enough; if the height space is too large, the speed of the air flow cannot maintain the direction from top to bottom, which is also not conducive to uniform adhesion. Therefore, the distance between the mesh plate 331 and the substrate needs to be controlled so that the organic precursor can form a cylindrical jet trajectory. The diameter of the mesh plate 331 is 70% - 90% of the diameter of the deposition chamber 1, which can reduce the deposition of gas on the inner wall of the chamber and improve the material utilization rate.

[0029] The transmission pipeline 3 is made of stainless steel material (inner diameter 5 - 10 mm), and a porous spray head 33 is arranged at the end of the transmission pipeline 3 to ensure the uniformity of the deposition film thickness (within ±3%) of the vapor in the deposition chamber 1.

[0030] As Figure 2 shown, the stage assembly 4 includes a tabletop 41 located at the upper part, a cooling chamber 42 located inside the tabletop 41, and a rotating mechanism 43 that drives the tabletop 41 to rotate around a vertical rotation axis. The vertical rotation axis is collinear with the vertical central axis of the mesh plate 331. A heat preservation layer 11 is provided on the outer wall of the deposition chamber 1.

[0031] The rotating mechanism 43 coats the film while the substrate rotates in the horizontal plane. Since the porous spray head 33 determines that the precursor vapor uniformly falls from a circular area, the substrate needs to rotate around the center of this circular area to improve the coating uniformity. The heat preservation layer 11 enables the deposition chamber 1 to maintain an appropriate temperature, reduces the solidification of the precursor vapor on the outer wall of the deposition chamber 1, and avoids the problem of uneven thickness caused by the precursor dripping onto the substrate.

[0032] As Figure 3As shown, inside the evaporation chamber 2, there is a crucible 21 for placing the organic precursor, a heating device for heating the organic precursor, and a pressure sensor 23 for measuring the internal pressure of the evaporation chamber 2. The heating device includes a plasma generator 22a located above the crucible 21 and a pulse heater 22b located below the crucible 21. There is a base 24 in the evaporation chamber 2 that raises the crucible 21, and the pulse heater 22b does not contact the base 24.

[0033] The crucible 21 is used to load the organic precursor. The precursor is mainly FAI, and MAI or FABr can also be selected. Ensure that the powder particle size is larger than the pore diameter of the crucible 21 to avoid overflow. The crucible 21 is a porous tungsten crucible and can hold multiple precursors for co-evaporation. The base 24 can make the upper part of the crucible 21 closer to the inlet of the transfer pipe 3 and is convenient for setting the pulse heater 22b.

[0034] The entire forming process of the perovskite layer is as follows: Device preparation: The deposition chamber 1 is evacuated to ≤1×10 -5 Pa, and the evaporation chamber 2 is filled with FAI and MAI powders respectively; configure the carrier gas system to provide high-purity N2 (or Ar) and set the flow rate to 5 sccm through the mass flow controller; the system is equipped with an independent pumping unit and temperature and pressure sensors to achieve independent control of the respective parameters of the evaporation chamber 2 and the deposition chamber 1.

[0035] Substrate treatment and inorganic layer deposition: Place the pre-cleaned ITO or FTO glass substrate on the table 41; deposit a 150-nm-thick PbI2 precursor layer by thermal evaporation or sputtering method, and control the deposition rate at about 1 Å / s to ensure that the pressure in the deposition chamber 1 remains at 1×10-5 Pa.

[0036] Evaporation of the organic precursor: S1. Evaporation: Place the organic precursor in the crucible 21, and perform low-temperature sublimation and molecular cluster depolymerization on the organic precursor through the heating device (plasma generator 22a and pulse heater 22b) to generate precursor vapor.

[0037] The pulse heater 22b (50 - 100 W, pulse width 0.2 - 0.5 s) is installed below the crucible 21, and the plasma generator 22a (10 - 30 W) is set above it to achieve low-temperature sublimation and molecular cluster depolymerization and reduce the thermal decomposition rate of the precursor.

[0038] S2. Carrier gas transportation: Using nitrogen or an inert gas (argon) as the carrier gas, send it into the transfer pipe 3 through the carrier gas guide pipe 31 to form a negative pressure, suck the precursor vapor into the deposition chamber 1, the precursor vapor accumulates in the porous spray head 33, and then uniformly passes through the mesh holes on the mesh plate 331 and sprays downward onto the substrate.

[0039] The heating mechanism 32 heats the precursor vapor in the transfer pipeline 3 to 100 - 120 °C to prevent the condensation of the organic precursor during transportation and avoid the decomposition of components. Since the inner diameter of the transfer pipeline 3 is always smaller than the radius of the deposition chamber 1 and the inner diameter of the evaporation chamber 2, the temperature of the precursor vapor is easier to maintain in a uniform state.

[0040] S3. Deposition: The substrate is pre-fixed above the table 41, and the rotation mechanism 43 controls the substrate to rotate around the vertical rotation axis. The refrigerant (10 - 50 °C) in the cooling chamber 42 keeps the substrate in a low-temperature state, so that the precursor vapor sublimates on the upper surface of the substrate.

[0041] The deposition chamber 1 can be maintained in a low-pressure environment of 10 -5 ~10 -4 Pa by a high-performance molecular pump and a cavity wall cold trap; the evaporation chamber 2 maintains a local pressure of 10 -3 ~10 -3 Pa to buffer the pressure fluctuations caused by the sublimation of the precursor. During the deposition process, an initial low deposition rate (about 0.5 Å / s) is used to form a nucleation layer, and then continuous deposition is carried out at about 1 Å / s to achieve the uniform growth of the organic film and ensure that the total deposition thickness accuracy meets the requirements.

[0042] Post-treatment: Close the valve between the external evaporation chamber 2 and the deposition chamber 1, stop heating each precursor, and keep the deposition chamber 1 evacuated for a period of time to remove the residual gas.

[0043] Annealing: Place the substrate in an inert atmosphere for annealing treatment at 100 - 170 °C for 20 minutes to make PbI2 fully react with the organic precursor to generate a high-quality perovskite phase.

[0044] Through the low-temperature carrier gas evaporation method combining the external evaporation chamber 2, low-temperature pulse heating, plasma assistance and carrier gas transportation, the present invention significantly reduces the decomposition risk of FAI and other organic precursors (MAI, FABr) under high vacuum conditions and alleviates the pressure fluctuation problem in the deposition chamber 1 caused by the sublimation of the precursor. Experiments show that this method makes the deposition rate stable and ensures that the stoichiometry and uniformity of the deposited film meet the requirements for the preparation of high-performance devices of perovskite solar cells. Through the method of the present invention, it is suitable for large-area continuous production, has high repeatability and feasibility, and provides an advanced and reliable solution for the organic precursor evaporation technology of perovskite solar cells.

[0045] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A perovskite cell organic precursor evaporation device, comprising a deposition chamber, an evaporation chamber, and a transmission pipeline connecting the evaporation chamber and the upper center of the deposition chamber, characterized in that: A carrier gas guide tube is provided on the transmission pipeline, a heating mechanism is provided in the transmission pipeline, a carrier assembly for horizontally placing the substrate is provided in the middle of the deposition chamber, and a porous spray head is provided at the outlet of the deposition chamber of the transmission pipeline, the bottom of the porous spray head is a mesh plate facing the upper surface of the substrate, the distance from the mesh plate to the substrate is 1 / 3 to 1 / 2 of the diameter of the deposition chamber, and is between 5 cm and 20 cm, and the diameter of the mesh plate is 70% to 90% of the diameter of the deposition chamber.

2. The perovskite cell organic precursor evaporation device according to claim 1, characterized in that: The stage assembly includes a table top located at the top, a cooling cavity located inside the table top, and a rotating mechanism for driving the table top to rotate around a vertical rotation axis, wherein the vertical rotation axis is colinear with a vertical center axis of the screen.

3. The perovskite cell organic precursor evaporation device according to claim 1, characterized in that: The outer wall of the deposition chamber is provided with a heat-insulating layer.

4. The perovskite cell organic precursor evaporation device according to claim 1, characterized in that: The evaporation chamber is provided with a crucible for placing an organic precursor, a heating device for heating the organic precursor, and a pressure sensor for measuring the internal pressure of the evaporation chamber.

5. The perovskite cell organic precursor evaporation device according to claim 4, characterized in that: The heating device comprises a plasma generator located at the upper part of the crucible and a pulse heater located at the lower part of the crucible. A base for raising the crucible is provided in the evaporation chamber, and the pulse heater is not in contact with the base.

6. The perovskite cell organic precursor evaporation device according to claim 4, characterized in that: The crucible is a porous tungsten crucible.

7. A method for evaporating an organic precursor for a perovskite battery, characterized in that: The method is performed using the evaporation device according to any one of claims 1 to 6, the steps comprising: S1, evaporation: placing the organic precursor in a crucible, sublimating the organic precursor at low temperature and depolymerizing the molecular clusters through the heating device, and maintaining the pressure in the evaporation chamber at 10 -3 ~10 -2 Pa, generating precursor vapor; S2, carrier gas delivery: nitrogen or an inert gas is used as a carrier gas and is delivered into the transmission pipeline through the carrier gas guide pipe to form a negative pressure, so that the precursor vapor is sucked into the deposition chamber, the precursor vapor is gathered in the porous shower head, and then evenly passes through the mesh holes on the mesh plate and is sprayed onto the substrate from top to bottom; S3, deposition: the substrate is pre-fixed above the table, the rotating mechanism controls the substrate to rotate around the vertical rotation axis, and the pressure in the deposition chamber is maintained at 10 -5 ~10 -4 Pa, the substrate is kept at a low temperature by the refrigerant in the cooling chamber, so that the precursor vapor condenses on the upper surface of the substrate.

8. The evaporation method of the organic precursor of the perovskite battery according to claim 7, characterized in that: The flow rate of the carrier gas is 5-50 sccm, the heating mechanism heats the precursor vapor to 100-120° C., and the inner diameter of the transmission pipeline is 5-10 mm.

9. The evaporation method of the organic precursor of the perovskite battery according to claim 7, characterized in that: The temperature of the refrigerant is 10-50° C., and the deposition chamber is a cylindrical vacuum chamber with an inner diameter of 30-50 cm.

10. The evaporation method of the organic precursor of the perovskite battery according to claim 7, characterized in that: The power of the plasma generator is 10-30 W, the power of the pulse heater is 50-100 W, and the pulse width is 0.2-0.5 s.

Images