High-Speed Hybrid CVD for Perovskite Solar Cell Modules

Abstract

Described herein are systems and methods for rapid hybrid chemical vapor deposition. In one embodiment, a first precursor material is deposited on a substrate. The substrate is placed in a holding portion of a heating device, and the heating device heats at least a portion of the holding portion. The second precursor material is placed in the holding portion of the heating device such that the organic compound is closer to a gas source of the heating device than the substrate. A gas flow is generated through the holding portion of the heating device. The heating portion is used to heat the portion of the holding portion containing the substrate and the second precursor material. During the heating process, at least a portion of the second precursor material deposits on at least a portion of the first precursor material.

Description

Technical Field

[0001] The present disclosure relates to a CVD (chemical vapor deposition) technique for fabricating perovskite solar cell modules.

Background Art

[0002] The approaches described in this section are approaches that can be pursued, but are not necessarily approaches that have already been conceived or pursued. Therefore, unless otherwise specified, none of the approaches described in this section should be considered suitable as prior art merely because they are included in this section. Furthermore, none of the approaches described in this section should be considered well understood, routine, or conventional merely because they are included in this section.

[0003] Perovskite, a low-cost material, can improve the performance of single-junction solar cells with a small area (0.09 cm 2 ) up to 25.2%. Assuming a module with an efficiency of 20% and a lifespan of over 15 years for 1 m 2 , the levelized cost of electricity (LCOE) expected is as low as 3.5 US cents / kWh (for comparison, the LCOE of grid power is 7.04 - 11.90 US cents / kWh, and the LCOE of c-Si solar cells is 9.78 - 19.33 US cents / kWh). This is better than the 5 US cents / kWh target set by the US Department of Energy for residential solar power generation in 2030. In recent years, in order to transition from small-area cells with desired performance to large-area modules, research has focused on scalable manufacturing methods for perovskite solar cell modules (PSMs). However, there is still a large gap between small-area cells and large-area modules.

[0004] To achieve scalable manufacturing, the performance degradation rate during upscaling is a crucial point. In mature solar power generation technologies (e.g., crystalline silicon solar cells, polycrystalline silicon solar cells, CdTe solar cells), the absolute performance degradation rate increases by approximately 0.8% per decade in terms of area conversion. If the same degradation rate can be achieved with perovskite solar cell technology, when scaling up from a prior art small-area cell (cell area 0.0937 cm 2 with 25.2% PCE), an energy conversion efficiency (PCE) of approximately 22% is expected for an area of about 1000 cm 2 . Currently, the highest PCE reported for such large-scale PSMs is 16.1% in a specified area of 802 cm 2 . To reduce the difference in PCE between small-area cells and large-area modules, a scalable manufacturing method for perovskite and other functional layers (e.g., electron transport layer (ETL), hole transport layer (HTL), electrodes, and surface modification) is required. For the scalable manufacturing of perovskite solar cells (PSCs), both solution-based and vapor-based processes such as doctor blade method, slot-die coating, spray coating, thermal evaporation, and hybrid chemical vapor deposition (HCVD) have been reported.

[0005] HCVD is a more promising method than solution-based methods due to advantages such as the ability to form a uniform film over a large area, low cost, solvent-free, and the ability to form tandem solar cells in combination with other thin-film solar cell technologies (e.g., thin-film silicon solar cells). Currently, the area increase in the degradation rate between small-area cells and large-area modules is 1.3% / 10 years, approaching that of other mature solar power generation technologies. HCVD is a two-step film formation process. In the first step, an inorganic precursor material (e.g., PbI 2 , PbCl 2, CsI, etc.) are formed into a film by thermal evaporation, spray coating, or spin coating. In the second step, an organic precursor material (e.g., FAI, MAI, MABr, etc. Here, FA is formamidinium and MA is methylammonium) is sublimated in the first heating zone of a CVD tubular furnace, and then is moved to the second heating zone by a gas flow (e.g., N 2 , Ar, or dry air). Here, a perovskite film grows by the reaction of the organic precursor vapor with the inorganic precursor previously formed into a film on the substrate. For the production of perovskite films, various HCVD techniques such as atmospheric pressure HCVD, low pressure HCVD, single zone HCVD, and double zone HCVD have been developed based on pressure and zone temperature. However, since any HCVD process usually requires a relatively long processing time (2 - 3 hours), the mass production capacity for manufacturing large - area solar cells is greatly limited. How to shorten the film - forming time is one of the issues for further development of HCVD. Furthermore, it has been found that when the film - forming time becomes long, it has an adverse effect on ETLs such as SnO 2 and TiO 2 , etc., and the performance of the solar cell module decreases. Also, due to the non - optimization of the interface between the ETL layer and the perovskite layer, hysteresis behavior has been observed. By using an additional buffer layer such as C 60 , the adverse effect of vacuum annealing on ETL can be reduced, and the performance of the HCVD - processed solar cell can be improved. However, this additional layer increases the cost and complexity of the film - forming process.

Summary of the Invention

[0006] The appended claims may function as an overview of the present disclosure.

Brief Description of the Drawings

[0007]

Figure 1

[0008]

Figure 2

[0009]

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following description, for the sake of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, that the practice of the present invention does not require these specific details. In other instances, well-known structures and devices are shown in block diagram form in order not to unnecessarily obscure the present invention.

[0011] <Overview>

[0012] One embodiment is a method for manufacturing a perovskite solar cell, comprising: a) depositing a first precursor material on a substrate; b) placing the substrate in a holding portion of a heating device, the heating device comprising a heating portion for heating at least a part of the holding portion; c) placing a second precursor material in the holding portion of the heating device such that the second precursor material is closer to a gas source of the heating device than the substrate; d) generating a gas flow through the holding portion of the heating device; and e) heating a part of the holding portion including the substrate and the second precursor material using the heating portion, wherein in step e), at least a part of the second precursor material is deposited on at least a part of the first precursor material on the substrate.

[0013] In one embodiment, the heating device includes a cooling unit, and f) after the step e), the method includes a step of cooling a part of the holding unit including the substrate using the cooling unit. In one embodiment, the cooling unit includes one or more fans, dry ice, or a means for supplying cooled dry air. In one embodiment, the heating unit includes an infrared heating unit. In one embodiment, one or more of the heating units or the cooling units are mechanically movable relative to the holding unit and are each moved to a position where heating or cooling is performed.

[0014] In one embodiment, the second precursor material includes formamidinium iodide, methylammonium iodide, methylammonium bromide, or formamidinium bromide. In one embodiment, the inorganic precursor material includes a layer including CsI and PbI 2 and. In one embodiment, the layer including CsI and PbI 2 is deposited by co-evaporation, spray coating, doctor blade method, or spin coating. In one embodiment, the heating device further includes a vacuum pump and a vacuum gauge, and in the step e), the vacuum pump and the vacuum gauge are used to control the degree of vacuum of the holding unit.

[0015] One embodiment is a heating device including a holding unit that holds an inorganic precursor material and an organic compound on a substrate, a heating unit that forms a perovskite layer on the substrate by heating at least a part of the holding unit including the substrate and the organic compound, a vacuum gauge that measures the degree of vacuum of the holding unit, and a vacuum pump that forms a vacuum in at least a part of the holding unit. In one embodiment, the heating unit includes an infrared heating unit. In one embodiment, the heating unit is mechanically movable relative to the holding unit. In one embodiment, the heating device further includes a cooling unit that cools a part of the holding unit including the substrate on which the perovskite layer is formed. In one embodiment, the cooling unit includes one or more fans, dry ice, or a device that supplies a stream of cooled dry air. In one embodiment, the cooling unit is movable relative to the holding unit.

[0016] <Structure of Perovskite Solar Cell>

[0017] In one embodiment, an n-i-p planar perovskite solar cell (PSC) has a structure in which a perovskite layer is sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL). In one embodiment, the PSC structure does not include a mesoporous structure. Thereby, a high-temperature step for generating the PSC structure becomes unnecessary.

[0018] FIG. 1 is a diagram showing an example of the structure of a planar perovskite solar cell. In one embodiment, the planar perovskite solar cell 100 has a lower layer 102 including an indium-doped tin oxide (ITO) substrate. The ITO substrate corresponds to a transparent conductive oxide (TCO). The ITO substrate may be sequentially washed with distilled water, acetone, and isopropanol and dried with N 2 gas. The second layer 104 may include a tin oxide (SnO 2 ) nanocrystal layer. The SnO 2 layer may be spin-coated on the ITO layer at 3000 rpm for 30 seconds and dried, for example, at 150° C. for 30 minutes. Although the TCO and ETL are shown in FIG. 1 as including the ITO layer and the SnO 2 layer, in other embodiments, any TCO and ETL suitable for the rapid hybrid CVD (RHCVD) process described herein may be included.

[0019] The perovskite layer 106 includes an inorganic precursor material and an organic precursor material deposited on the ETL by the systems and methods described herein. In one embodiment, the perovskite layer 106 may include a combination of cesium iodide, formamidinium (FA), and lead iodide. In other embodiments, different combinations of organic precursor materials and inorganic precursor materials may be included, such as lead chloride as an inorganic material or methylammonium as an organic material. The composition of the perovskite layer is exemplified, for example, by Cs 0.1 FA 0.9 PbI 3 and the like.

[0020] The hole transport layer 108 includes a hole transport material disposed on the perovskite layer 106. The hole transport layer 108 may be spin-coated on the perovskite layer 106, for example, at a rotational speed of 300 rpm for 30 seconds. In one embodiment, the hole transport layer 108 includes a chlorobenzene solution of spiro-MeOTAD, tributyl phosphate (TBP), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). As an example, the solution may contain 20 mg of spiro-MeOTAD, 11.5 μL of TBP, and 7 μL of LiTFSI in 0.4 mL of chlorobenzene. The upper layer 110 may include a back contact electrode, such as a layer of gold having a thickness of 100 to 120 nm.

[0021] <Rapid Hybrid Chemical Vapor Deposition Apparatus>

[0022] FIG. 2 is a diagram showing an example of an apparatus for manufacturing a perovskite solar cell module. In one embodiment, the apparatus 200 has a rapid thermal annealing (RTA) tubular furnace. The apparatus 200 has a single-zone or multi-zone tube 202. The tube 202 may include any material that can be heated to a desired temperature and transfer heat to an object inside. The tube 202 may be, for example, a quartz tube.

[0023] The inlet 204 has an opening through which gas can be injected into the tube 202. The inlet 204 may have a location where a vacuum gauge (not shown) for measuring the pressure inside the tube 202 can be disposed. The outlet 206 has an opening to which a vacuum pump (not shown) for reducing the pressure inside the tube 202 can be attached. The outlet 206 may further have an opening through which gas can flow out of the tube 202.

[0024] The heating system 208 has one or more heating devices configured to apply heat to a section of the tube 202. In one embodiment, the heating system 208 has an infrared heating system. The heating system 208 may be mechanically movable freely with respect to the tube 202. The heating system 208 may be attached to one or more rails such that the heating system 208 can move freely along the horizontal axis of the tube 202. The movement of the heating system 208 may be mechanically controlled or may be automatically controlled by a computing device.

[0025] The cooling system 210 has one or more cooling devices that cool a portion of the tube 202. In one embodiment, the cooling system 210 has one or more fans. The cooling system 210 may be mechanically movable freely with respect to the tube 202. The cooling system 210 may be attached to one or more rails such that the cooling system 210 can move freely along the horizontal axis of the tube 202. The movement of the cooling system 210 may be mechanically controlled or may be automatically controlled by a computing device. In one embodiment, the cooling system 210 and the heating system 208 are attached such that movement of the heating system 208 causes movement of the cooling system 210.

[0026] The substrate 212 comprises one or more solar cell modules. A perovskite film is formed on this solar cell module by the method described herein. In one embodiment, the substrate 212 is disposed within the platform of the apparatus 200. In one embodiment, this platform is controllable. Thereby, during execution of the method described herein, the substrate can be moved within the apparatus 200. In one embodiment, the substrate 212 is pre-coated with an inorganic precursor material such as a mixture of CsI and PbI 2 and the like.

[0027] The evaporation material 214 includes an organic precursor material for sublimation disposed in the apparatus 200. The organic precursor material may include formamidinium iodide, methylammonium iodide, methylammonium bromide, or other suitable organic precursor materials. The organic precursor material may be disposed upstream of the substrate 212 with respect to the gas flow passing through the apparatus 200. In one embodiment, the evaporation material 214 is disposed on a platform within the apparatus 200. In one embodiment, this platform is controllable. Thereby, the evaporation material can be moved within the apparatus 200 during the execution of the method described herein.

[0028] <Rapid Hybrid Chemical Vapor Deposition>

[0029] FIG. 3 is a diagram showing an example of a rapid hybrid chemical vapor deposition process. The example of FIG. 3 includes one implementation of the rapid hybrid chemical vapor deposition described herein. In other examples, different materials, different types of heating or cooling devices, different types of moving mechanisms, multi-zone tubes, and / or other variations may be included.

[0030] In step 302, the solar cell substrate module and the evaporation material are disposed in the chamber. The chamber may include a chamber of any material suitable for the vacuum pressure and heating methods described herein. In FIG. 3, a cylindrical tube chamber is shown, but the chamber may have other shapes such as a cube or a hexagonal prism. Further, although the cylindrical tube is described as being made of quartz, other materials may be used.

[0031] The solar cell substrate module is SnO 2It may contain indium-doped tin oxide coated with a layer. The vapor deposition material may contain an organic precursor material in powder form, for example, 0.1 g of formamidinium iodide for a 5 cm × 5 cm substrate module. The vapor deposition material may be arranged to be located upstream of the gas flow with respect to the solar cell substrate module. For example, when drawing gas into the apparatus using a vacuum pump, the vapor deposition material may be arranged closer to the gas source than the solar cell substrate module. Thereby, the gas flow can reach the vapor deposition material before reaching the solar cell substrate module.

[0032] In step 304, a carrier gas flow is generated in the chamber. As the carrier gas, any gas suitable for generating an air flow, such as N 2 , Ar, O 2 etc., can be used. The carrier gas flow can be generated by any means suitable for generating a gas flow. As an example, the degree of vacuum can be adjusted using a vacuum pump and maintained at around 10 Torr.

[0033] In step 306, the heating system starts heating the solar cell substrate module and the vapor deposition material. For example, a movable infrared heating mechanism can be moved so that heat is directly applied to both the substrate module and the vapor deposition material. Additionally, or alternatively, the heating system arranged at a position to heat the solar cell substrate module and the vapor deposition material can be activated to start the heating process. Additionally, or alternatively, the solar cell substrate module and the vapor deposition material may be moved to a position where they are heated by the heating system, for example, through a movable platform in the chamber. In FIG. 3, an infrared heating mechanism is shown as the heating mechanism, but other mechanisms may be used to heat the solar cell substrate module and the vapor deposition material.

[0034] In one embodiment, the heating mechanism and the cooling mechanism are configured to move together. For example, the heating mechanism and the cooling mechanism may be attached to each other along a rail so that the two mechanisms can move along the horizontal axis of the chamber. In other embodiments, the heating mechanism and the cooling mechanism are stationary, and the solar cell substrate module and the vapor deposition material may move along the horizontal axis of the chamber.

[0035] In one embodiment, the heating in step 306 can be optionally performed within 1 to 20 minutes. The lower the temperature, the longer the change time of the perovskite. As an example, when the temperature is 160°C, heating is performed for 6 minutes, while at 170°C, heating is performed for 2 to 3 minutes.

[0036] In step 308, the heating mechanism stops heating the solar cell substrate module and the vapor deposition material, and the cooling mechanism starts cooling the solar cell substrate module. For example, the heating mechanism may stop, and the cooling mechanism may move to a position where it can at least cool the solar cell substrate module. Additionally, or alternatively, the solar cell substrate module may move to a position where the cooling mechanism can cool the solar cell substrate module, such as via a movable platform. The cooling mechanism may include one or more fans or any cooling mechanism.

[0037] In the embodiments, the movable heating mechanism and cooling mechanism, and / or the movable platform for the solar cell substrate module and the vapor deposition material have been described. However, in other embodiments, the chamber may have stationary components. For example, the cooling mechanism and the heating mechanism may both be configured to target the same part of the chamber. In step 306, the heating mechanism may be activated to thereby heat the solar cell substrate module and the vapor deposition material. Then, in step 308, the heating mechanism may be stopped and the cooling mechanism may be activated.

[0038] After performing a rapid hybrid chemical vapor deposition process as shown in FIG. 3, the perovskite film may be washed or heated to remove the remaining formamidinium iodide. The hole transport material may be spin-coated on top of the perovskite layer. After the hole transport layer is deposited on top of the perovskite, a back contact electrode, such as a layer of gold 120 nm thick for example, may be added on top of the hole transport layer.

[0039] <Advantages of an embodiment>

[0040] The mechanisms and methods described herein can improve the hybrid chemical vapor deposition process for manufacturing perovskite solar cells. By using the rapid hybrid chemical vapor deposition process, the film formation time of the perovskite layer is shortened from several hours to within 10 minutes. Furthermore, this process can be scaled up to manufacture multiple perovskite solar cell modules at once with minimal hysteresis and without significantly reducing efficiency. Additionally, by using an infrared heating mechanism, a perovskite film of better quality can be manufactured compared to a perovskite film post-annealed by conventional methods. This is due to two effects of infrared heating: the promotion of perovskite film formation and the improvement of perovskite film crystallinity due to the perovskite film being heated uniformly.

[0041] Furthermore, since the processing time in the CVD tube furnace is short, the exposure time of the glass / ITO / SnO 2 electron transport layer substrate in vacuum is shortened. As a result, the electron transport layer can be maintained in a high-quality state with a low density of gap states. The PSM has been demonstrated to have an efficiency of 12.3% in a predetermined region of 22.4 cm 2 . Also, the performance of this PSM is maintained at 90% of the initial value even after steady-state output operation under continuous light irradiation for over 800 hours. 2

[0042] The n-i-p planar PSC structure with a perovskite layer between the ETL and the HTL does not have a mesoporous structure. Therefore, by using this structure, a high-temperature heating process becomes unnecessary. Also, by using a small amount of Cs cations, the stability of the perovskite film is improved.

Claims

1. A method for manufacturing a perovskite solar cell, comprising: a) depositing an inorganic precursor material on a substrate; b) placing the substrate in a holding part of a heating device, the heating device comprising a heating part for heating at least a part of the holding part; c) placing an organic precursor material in the holding part of the heating device such that the organic precursor material is closer to a gas source of the heating device than the substrate; d) generating a gas flow through the holding part of the heating device; e) heating, using the heating part, a part of the holding part including the substrate and the organic precursor material; wherein the substrate and the organic precursor material disposed in the holding part are mechanically movable relative to the heating part, or the heating part is mechanically movable relative to the substrate and the organic precursor material disposed in the holding part; in step e), at least a part of the organic precursor material reacts with at least a part of the inorganic precursor material on the substrate to grow a perovskite film; the heating device comprises a cooling part; f) after step e), cooling, using the cooling part, a part of the holding part including the substrate; wherein the cooling part is mechanically movable relative to the holding part, or the substrate and the organic precursor material disposed in the holding part are mechanically movable relative to the cooling part; in step f), moving the cooling part to a position where the cooling part cools a part of the holding part including the substrate, or moving a part of the holding part including the substrate, a method for manufacturing a perovskite solar cell.

2. The method for manufacturing a perovskite solar cell according to claim 1, wherein the cooling part includes one or more fans, dry ice, or a means for supplying cooled dry air.

3. The method for manufacturing a perovskite solar cell according to claim 1 or claim 2, wherein the cooling part is mechanically movable relative to the holding part; in step f), moving the cooling part to a position where the cooling part cools a part of the holding part including the substrate.

4. The method for manufacturing a perovskite solar cell according to claim 1, wherein the heating part includes an infrared heating part.

5. The method for manufacturing a perovskite solar cell according to claim 1 or 4, wherein: the heating unit is movable relative to the holding unit; in step e), the heating unit is moved to a position where the heating unit heats a part of the holding unit including the substrate and the organic precursor material, the method for manufacturing a perovskite solar cell.

6. The method for manufacturing a perovskite solar cell according to claim 1, wherein: the organic precursor material includes formamidinium iodide, methylammonium iodide, methylammonium bromide, or formamidinium bromide, the method for manufacturing a perovskite solar cell.

7. The method for manufacturing a perovskite solar cell according to claim 1, wherein: the inorganic precursor material has one or more of a CsI layer, a PbI2 layer, a PbBr2 layer, or a CsBr layer, the method for manufacturing a perovskite solar cell.

8. The method for manufacturing a perovskite solar cell according to claim 1, wherein: the inorganic precursor material has a layer including CsI and PbI2; the layer including CsI and PbI2 is deposited by co-evaporation, spray coating, doctor blade method, or spin coating, the method for manufacturing a perovskite solar cell.

9. The method for manufacturing a perovskite solar cell according to claim 1, wherein: the heating device further includes a vacuum pump; a vacuum gauge; and in step e), the vacuum pump and the vacuum gauge are used to control the degree of vacuum of the holding unit, the method for manufacturing a perovskite solar cell.

10. A heating device, comprising: a holding unit that holds an inorganic precursor material and an organic precursor material on a substrate; a heating unit that heats at least a part of the holding unit on which the substrate and the organic precursor material are disposed, and reacts at least a part of the organic precursor material with at least a part of the inorganic precursor material on the substrate to form a perovskite layer on the substrate; a vacuum gauge that measures the degree of vacuum of the holding unit; a vacuum pump that forms a vacuum in at least a part of the holding unit; wherein the substrate and the organic precursor material disposed on the holding unit are mechanically movable relative to the heating unit, or the heating unit is mechanically movable relative to the substrate and the organic precursor material disposed on the holding unit; and further includes a cooling unit that cools a part of the holding unit including the substrate on which the perovskite layer is formed on the substrate. ​ The heating device is such that the cooling unit is mechanically movable relative to the holding unit, or the substrate and the organic precursor material disposed on the holding unit are mechanically movable relative to the cooling unit. **Claim 11**: The heating device according to claim 10, wherein the heating unit includes an infrared heating unit. **Claim 12**: The heating device according to claim 10 or claim 11, wherein the heating unit is mechanically movable relative to the holding unit. **Claim 13**: The heating device according to claim 10, wherein the cooling unit includes one or more fans, dry ice, or a device for supplying a cooled dry air stream. **Claim 14**: The heating device according to claim 10 or claim 13, wherein the cooling unit is movable relative to the holding unit.

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