TWI457452B - Solar cell cuprous oxide (Cu 2 O) film coating method - Google Patents

Description

Solar cell cuprous oxide (Cu 2 O) thin film coating method

The invention relates to a solar cell thin film coating technology, in particular to a method for depositing a Cu ₂ O thin film in a single process.

Solar film is a hot research topic, and most of them use single crystal germanium or polycrystalline germanium as the substrate, which is costly. Cuprous oxide (Cu ₂ O) is a direct energy gap P-type semiconductor material, which is a non stoichiometric defect semiconductor with an optical energy gap of about 2.1-2.5 eV. It is cost-effective and non-toxic; its original copper material is abundant in nature, and it is also a great advantage, and has a relatively high light absorption coefficient in the visible range, so the main application can be used to manufacture solar cell components. In principle, the solar photovoltaic conversion law of Cu ₂ O thin film can reach up to 20%, so many research units are attracted to development. However, the solar photovoltaic conversion law of the actual module is far lower than the theoretical value, so there are many problems in Cu ₂ O film. Still to be overcome.

Conventional physical vapor deposition (PVD) coating technology often uses plasma to assist the coating. Since the particles in the plasma have high energy and the energy exceeds the intermolecular chemistry, a stable chemical bond can be formed, and various high performances can be easily deposited. The compound film, and the film quality of the film is fine, compact and strong, and has ceramic properties, and has good performance in mechanical, anti-corrosion and release properties, so it is widely used in the protection and decoration of industrial metals. Although plasma has great benefits for PVD coating, if the plasma density is low (such as magnetron sputtering, the free rate is 5%), the coating effect is similar to evaporation, and the reactive film or film adhesion is two. Poor quality, affecting the scope of application.

The traditional solar cell cuprous oxide film is grown by reactive DC [1] or RF high-frequency magnetron sputtering [2] coating system. Two processes are commonly used. One is to use high temperature process temperature to be 500 ° C to 600 ° C to deposit. Deposition of the film, but the process of the substrate is glass, cooling takes time, and the quality of the glass is also a big test; the second is to use a low temperature 50 ° C to 300 ° C deposition process, after deposition still need to add a high temperature 300 ° C annealing step, In order to obtain the main structure Cu ₂ O film, it is also time consuming and costly. If only the low temperature process is used without the annealing step, the microstructure of the deposited film is disordered, Cu, Cu ₂ O, CuO and Cu ₄ O ₃ may appear, which affects the photoelectric properties of the film. Therefore, it is necessary to seek a simple process and achieve the main structure phase Cu. ₂ O film is currently the most demanding technology in the solar industry.

[1] A.A. Ogwu, T.H. Darma and E. Bouquerel; Journal of Achievements in Materials and Manufacturing Engineering; Volume 24, Issue 1, Sep. 2007.

[2] JM Chappe ' , N. Martin, J. Lintymer, F. Sthal, G. Terwagne, J. Takadoum, Applied Surface Science 253 (2007) 5312-5316.

Based on the above problems, the inventors have proposed a solar cell cuprous oxide (Cu ₂ O) thin film coating method to overcome the drawbacks of the prior art.

In recent years, due to the advancement of power supply technology, a new coating technology has been produced, called "High Power Impulse Magnetron Sputtering Technology (HIPIMS)". In response to the above-mentioned solar Cu ₂ O thin film technology requirements, the present invention is to provide A solar cell cuprous oxide (Cu ₂ O) thin film coating method is capable of depositing a Cu ₂ O structure film by high-power pulsed magnetron sputtering, and the main considerations thereof are four:

First, the process plasma density is adjustable, the pulse power of this device can reach MW series, the plasma produced is much higher than the traditional PVD method, and the process of subverting the traditional fixed plasma density ratio depends on the demand. , can be elastically adjusted from 5% to 100%.

Second, the process temperature is adjustable, the device uses the pulse wave time width of the pulse power supply, the modulation load rate is used as the workpiece temperature control, the process temperature can be between 50 ° C ~ 400 ° C, and the pulse plasma still maintains a certain intensity, Achieve the deposition effect.

Third, simplify the process, without the traditional "plasma activation" step, in the various plastic, glass surface, with nitrogen plasma or oxygen plasma pretreatment (pretreatment) to open the surface molecular bonds, and the next step of the sediment production When the device of the present invention is coated on the workpiece, various functional films can be directly deposited.

Fourth, the sedimentary particle energy is uniform, this is the most critical technology. In the present invention, the plasma power source generates hundreds of times the plasma density of the conventional plasma, and can establish a self-coupled negative voltage on the surface of the workpiece (several volts to several tens of volts). ), no additional bias auxiliary device is required, the voltage level is determined by the pulse plasma density, accurately providing the uniformity energy of the deposited particles, and the reactive film structure is differentiated to obtain the ideal coating quality.

The self-induced negative voltage on the workpiece, this low voltage has a very good effect on the chemical reaction of the coating. The energy of the copper deposited particles is close to the copper oxidation energy, and the Cu ₂ O structure is easily formed. On the other hand, if the external bias voltage is deliberately used to give the workpiece a negative voltage, the self-coupled negative voltage will reverse the charge to the bias power supply, causing the bias power supply to fail to add a voltage value or be damaged by the reverse current. Conventional low-neutral magnetron sputtering (5% ion) has a wide energy distribution, and the workpiece bias voltage is low, and the workpieces are mostly electrical insulators, which cannot be supplied by an external power source, so it is difficult to implement the Cu ₂ O main structure. the proposed method of the present invention is based preferably have the ability-plated (prefer orientation) film of a variety of specific structures, such as structural strength of the film the highest Cu ₂ O Cu ₂ O (200) film, or Cu ₂ O (111) film or the like .

Therefore, the technology proposed by the present invention can reduce the cost of coating and increase the business opportunities.

In order to achieve the above object, the present invention provides a solar cell cuprous oxide (Cu ₂ O) thin film coating method, which is a vacuum magnetron sputtering process technology method, which can deposit cuprous oxide in a single process on various material workpieces. The process requires a vacuum system in which a high-power pulsed magnetron sputtering source, a gas supply source, and a substrate carrier are disposed. Under a suitable vacuum environment, argon gas and oxygen are charged, and a high-power pulsed magnetron sputtering source is activated to generate plasma. Copper and oxygen ions in the plasma are combined and deposited into Cu ₂ on a carrier substrate with an even negative bias voltage. O film; in the initial stage of the process, according to the color of the copper oxide film in the coating to adjust the amount of oxygen, the copper oxide film color is transparent (slightly orange), no need to adjust the amount of oxygen, continue to deposit to the expected time .

The solar cell Cu ₂ O coating of the invention does not require a conventional process, including activation, plasma cleaning, and post-coating annealing, and can directly deposit a Cu ₂ O film, which has a short process time and saves process cost.

In some embodiments, the process technology of vacuum magnetron sputtering requires a high power pulsed magnetron sputtering source, including a magnetron sputtering source and a high power pulse power source; wherein the magnetron sputtering source is provided with a copper The target has a purity of 99.5% or more. High-power pulsed power supply can use dc power supply and one pulse The pulser can be combined with a combination, or both can be integrated into one power supply. The high-power pulse power supply uses negative unipolar mode output, pulse-on-time from 50μs to 10ms, and pulse-off time from 50μs to 100ms.

In some embodiments, a gas supply source may be included, including two gases, namely argon gas and oxygen gas, and the volume percentage of oxygen and argon gas is proportional to the magnetron sputtering source power and the workpiece placement distance, and oxygen. The volume percentage of argon may range from 10% to 40%.

In some embodiments, a substrate carrier may be further included, which is electrically insulated from the cavity, and the potential of the substrate carrier is floating, without any power supply, and the substrate carrier is pulsed. Under the impact of the slurry, a self-coupled negative bias voltage of tens to hundreds of volts is instantaneously generated to provide copper oxygen ion energy in the plasma to produce a combined deposition on the substrate.

The process technology method of vacuum magnetron sputtering can be divided into three steps: vacuuming, plasma coating and film transparency parameter adjustment; vacuum background pressure is lower than 3×10 ^-5 torr to carry out the next coating step. The plasma coating adopts a high-power pulsed magnetron sputtering method. The types of magnetron sputtering sources may include a planar circuit, a planar rectangular shape or a columnar type, and one or more combined systems may be coated. The third step of the transparent parameter adjustment is to use the difference in the color depth of the film at the initial stage of the coating, and to instantly adjust the oxygen amount or the magnetron sputtering source power to achieve the optimal transparency of the film. The detection of film transparency can be measured by a naked eye or an optical metric.

Cu ₂ O coating technology can be applied to a variety of substrates, including glass, metal and plastic materials. Among them, plastic materials include PP, PE, PC, PS, PEI, PET, ABS, PEEK, NPPA, LCP, Nylon and so on.

In some embodiments, a high power pulsed magnetron sputtering method is employed. The plasma itself has a high density and has a coating distance farther than conventional magnetron sputtering. The distance from the substrate to the target can range from 5 cm to 60 cm.

In some embodiments, the solar cell Cu ₂ O coating comprises various Cu ₂ O structures including Cu ₂ O(111), Cu ₂ O(110), Cu ₂ O(200), and Cu ₂ O(220). Etc., and the present invention utilizes different pulsed plasma strengths, causes the substrate to self-occasion bias value characteristics, changes the coating ion energy, and has the ability to plate a film of various specific structures, such as Cu ₂ O in a Cu ₂ O film. The film with the strongest phase structure.

In addition to the solar cell Cu ₂ O coating, various CuO and Cu ₄ O ₃ coatings are also available.

While the invention has been described in terms of several preferred embodiments, the preferred embodiments of the present invention It is not intended that the invention be limited to the following drawings and embodiments.

1 is a schematic view showing a process of depositing a solar cell Cu ₂ O thin film on a glass substrate by high-power pulsed magnetron sputtering in the present invention, and the coating system may include a vacuum chamber 1, a magnetron sputtering source 2, and a high power. Pulse plasma 3, workpiece holder 4, high power pulse power source 5, DC power source 6, pulse power source 7, vacuum pumping system 8, target (Cu) 9, gas supply source 10.

There is mainly a vacuum chamber 1 and a gas supply source 10 of the coating system, and the vacuum is maintained by the vacuum pumping system 8. A group of magnetron sputtering sources 2 are mounted on the wall of the vacuum chamber 1, a special high-power pulse. Power supply 5 provides negative power The magnetron sputtering source 2 is pressed to generate a pulsed plasma 3, and the high-power pulse power source 5 is composed of a group of DC power sources 6 and a set of pulse power sources 7, and a set of (potential floating) workpiece fixtures 4 are used for loading. The workpiece is basically a conventional magnetron plating system. The magnetron sputtering power source 2 is a high-power pulse power source 5, which becomes the high-power pulse magnetron coating system of the present invention.

The operating voltage of the magnetron target of the high-power pulsed magnetron sputtering technology is about several hundred volts higher than the conventional magnetron sputtering voltage. Therefore, the system of the present invention has higher electron energy and long life, and can be freed from a wider area. The traditional coating system has a much higher plasma density, which is Abnormal glow discharge in the vacuum discharge category. The coating distance can also be several times larger than the conventional magnetron. Therefore, the workpiece system of the coating system of the present invention can be used not limited to 5~7 cm from the front of the target. distance.

The process of the present invention is divided into three steps. As shown in FIG. 2, there is a 3 ^" (3 吋) copper target magnetron source coating, and the 5 x 5 cm glass workpiece is placed at a distance of 18 cm from the target. The steps include: Step S1: System vacuuming Step: vacuuming the coating system until the vacuum background pressure is nearly 3×10 ^-5 torr; Step S2: high-power pulse plasma deposition film step: first filling the gas supply source 10 with argon gas 270 sccm and oxygen gas 50 sccm into the coating system The gas pressure reaches 2.7×10 ^-3 torr, and the high-power pulsed magnetron sputtering source 2 is activated to generate plasma. The copper and oxygen ions in the plasma are combined and deposited into a film on a substrate substrate with an even negative bias. The power pulse power source 5 is formed by combining the DC power source 6 and the pulse power source 7. The on/off time of the voltage pulse wave outputted by the pulse power source 7 is set at 200/3000 μs (microseconds), when the pulse power source 7 When the pulse voltage is output to the surface of the Cu target 9 of the magnetron sputtering source 2, the surface is discharged to generate plasma, and when the voltage output value is 550V, a corresponding peak current of 12A is generated during the pulse width time; Step S3: transparency parameter adjustment step: initial stage of coating, micro The whole process oxygen or peak current parameters, the film does not become CuO black or copper (including Cu), after a good process parameters adjusted, plating time of 40 minutes to complete a Cu ₂ O coating, removed of the film thickness of 0.4 m, the color Transparent orange.

In step S2, the pulse power source 7 is mainly composed of a large capacitor and a fast switch (not shown), and the required power is provided by the DC power source 6, and the pulse power source 7 can set the charge of the large capacitor (not shown). The pulse wave (tens to hundreds of microseconds) is instantaneously released, and the magnetron sputtering source 2 transmitted in a vacuum environment generates plasma and obtains a higher voltage, current value, and plasma density, plasma density than a conventional power source. High film quality and film adhesion are very beneficial; because the pulse type power supply is used, the power output has a gap, although the instantaneous pulse power is high, tens to hundreds of times higher than the traditional magnetron sputtering source. However, the average power of the power source is the same as the conventional one, so the magnetron sputtering source and the workpiece are not overloaded to generate high temperature.

The type of the magnetron sputtering source 2 may include a planar circuit, a planar rectangular shape or a columnar type, and one or more combined systems may be coated.

The process technology of the present invention measures the microstructure of the film by XRD after the solar cell Cu ₂ O coating is completed. The result is shown in FIG. 3 , wherein the vertical axis in FIG. 3 represents the X-ray diffraction intensity, and the horizontal axis represents X. The light diffraction angle, which shows that Cu ₂ O(111) has the strongest structural strength at a diffraction angle of 37°, and the Cu ₂ O(200) intensity is second in the diffraction angle of 43°, and there is still a small intensity. Cu ₂ O (220) and Cu ₂ O (110), FIG. 3 shows that the film has no other CuO and Cu material structures, and only Cu ₂ O structure exists; therefore, FIG. 3 can prove that the process technology of the present invention can be High-power pulsed magnetron sputtering process technology produces a single reactive film that is simpler and more cost effective than traditional processes.

In addition, the process technology of the present invention can be applied to various glass, metal and plastic materials, and the plastic materials can include PP, PE, PC, PS, PEI, PET, ABS, PEEK, NPPA, LCP, Nylon, etc. .

Although the present invention has been explained in connection with the preferred embodiments, it is not intended to limit the invention. It should be noted that many other similar embodiments can be constructed in accordance with the teachings of the present invention, which are within the scope of the present invention.

1‧‧‧vacuum chamber

2‧‧‧Magnetron sputtering source

3‧‧‧High power pulse plasma

4‧‧‧Workpiece fixture

5‧‧‧High power pulse power supply

6‧‧‧DC power supply

7‧‧‧ pulse power supply

8‧‧‧Vacuum pumping system

9‧‧‧ Target (Cu)

10‧‧‧ gas supply

S1‧‧‧ system vacuuming step

S2‧‧‧High-power pulse plasma deposition of Cu ₂ O film

S3‧‧‧Transparent parameter adjustment steps

1 is a schematic view showing a process of depositing a solar cell Cu ₂ O thin film on a glass substrate by high power pulsed magnetron sputtering in the present invention.

2 is a flow chart showing the steps of the process for depositing a solar cell Cu ₂ O film according to the present invention.

Fig. 3 is a view showing the XRD structure of the Cu ₂ O thin film of the solar cell of the present invention.

S1‧‧‧ system vacuuming step

S2‧‧‧High-power pulse plasma deposition of Cu ₂ O film

S3‧‧‧Transparent parameter adjustment steps

Claims (5)

A solar cell cuprous oxide (Cu ₂ O) thin film coating method is carried out in a coating system, the method comprising the following steps: a system vacuuming step: vacuuming the coating system until the vacuum background pressure is nearly 3 ×10 ^-5 torr; a high-power pulse plasma deposition film step: firstly, a gas supply source of the coating system is filled with argon gas 270 sccm and oxygen gas 50 sccm to make the gas pressure in the coating system reach 2.7×10 ^-3 torr Starting a high-power pulsed magnetron sputtering source of the coating system to generate plasma, and copper and oxygen ions in the plasma are deposited and deposited into a film on a substrate substrate of an even negative bias voltage, and the coating system is The start/stop time (on/off time) of a voltage pulse wave outputted by a pulse power supply is set at 200/3000 μs (microseconds), and when one pulse voltage supplied by the pulse power source is 550 V, there is one corresponding one. Peak current 12A; and a transparency parameter adjustment step: at the initial stage of the coating, the oxygen or the peak current parameter is finely adjusted so that the film does not become CuO black or copper (including Cu), and the process parameters are adjusted. After Plating time of 40 minutes, complete plating Cu ₂ O, extracted amount of film thickness of 0.4 m, was transparent and slightly orange color; wherein the coating system further comprising a substrate stage, based coating systems with one of the cavities The isolation is electrically insulated, the potential of the substrate carrier is floated, and no power source is connected, and the substrate carrier generates a self-coupled negative bias voltage of tens to hundreds of volts under the impact of pulsed plasma. The copper oxide ion energy in the plasma is provided to produce a combined deposition on a substrate. The method of claim 1, wherein the method is as follows At least one of the materials is coated: various glass, metal and plastic materials, including PP, PE, PC, PS, PEI, PET, ABS, PEEK, NPPA, LCP, Nylon. The method of claim 1, wherein the coating system further comprises a high power pulsed magnetron sputtering source having a magnetron sputtering source and a high power pulse power source; wherein The high-power magnetron sputtering source is equipped with a copper target having a purity of 99.5% or more; the high-power pulse power source is combined with a dc power supply and a pulser, and the high-power pulse power supply is combined. Negative voltage unipolar mode output (negative unipolar), pulse-wave width (on-time) from 50μs to 10ms, pulse-wave off-time (off-time) range from 50μs to 100ms. The method of claim 1, wherein the volume percentage of oxygen and argon is proportional to a magnetron sputtering source power and a workpiece placement distance, and the volume percentage of the oxygen and argon ranges from 10% to 40%. The method of claim 1, wherein the film is a Cu ₂ O structure comprising at least Cu ₂ O(111), Cu ₂ O(110), Cu ₂ O(200), and Cu ₂ O. (220).