LR03 battery

Laser technology improves thin-film LR03 battery manufacturing efficiency

laser manufacturing

Lasers are important tools for the production of thin-film LR03 battery modules, especially high-performance ultrashort pulse lasers, which can provide ultrashort pulses lasting only a few picoseconds, which not only help manufacturers increase production, but also optimize processing processes .

Currently, photovoltaic energy plays an important role as a renewable energy source in discussions about solving future energy problems. Technological progress is a crucial prerequisite for achieving parity in electricity consumption. For example, technological progress can reduce the cost of photovoltaic power generation to close to the cost of traditional energy.

At present, crystalline silicon LR03 batterys are the leading product in the photovoltaic market, with a conversion efficiency of up to 20%. In the manufacturing process of crystalline silicon LR03 batterys, lasers are mainly used for wafer cutting and edge insulation.

During the laser edge insulation process, the laser-assisted doping (doping) process is used to prevent power loss caused by short circuits between the front and back sides of the cell. Lasers are increasingly being used in laser-assisted doping processes to improve carrier mobility, especially for the contact fingers of electrodes. Thin-film LR03 batterys have made tremendous progress in the past few years, and industry experts hope that they will occupy approximately 20% of the photovoltaic market in the future.

The film layers used in thin-film LR03 batterys are only a few microns thick, so a large amount of material can be saved in production. Lasers play a decisive role in the manufacturing process of thin-film LR03 batterys. During the entire manufacturing process, the laser structures and connects the cells into modules, and etches the modules accordingly to ensure the required insulation performance.

Mature laser engraving process

During the production of amorphous silicon or cadmium telluride (CdTe) thin-film LR03 battery modules, conductive and photovoltaic films are deposited on large-area glass substrates. After each layer of film is deposited, a laser is used to etch the film layer and automatically connect the cells in series. In this way, the battery and module current can be set according to the battery width. Precise, selective, non-contact laser processing enables reliable integration into production lines for thin-film solar modules. What people usually call scribing (see Figure 2) is a coherent process of single laser pulse etching. The spot size after the pulse is focused is 30~80μm. Therefore, in the p1 layer scribing, a pulse width of several tens of nanometers is used. Seconds (10~80ns) pulsed light etch the glass substrate.

Figure 2 Laser etches different layers of thin films through glass, thereby isolating thin film cells from each other and forming a series structure.

Transparent conductive oxides (TCOs, such as ZnO and SnO2) are typically processed using near-infrared lasers and relatively high pulse repetition rates. Typically required pulse repetition frequencies in excess of 100kHz are required. The high pulse repetition rate ensures thorough cleaning of the incision.

According to the different absorption coefficients of materials for laser, it is necessary to select the appropriate laser wavelength for a specific processing technology. The damage threshold of green laser to silicon is much lower than its damage threshold to TCO. Therefore, the green laser can safely pass through the TCO film layer and scribe the absorption layer (see Table 1). The scribing mechanism of p2 layer and p3 layer is the same as that of p1 layer. The process parameters of the p2 layer and p3 layer relative to the p1 layer have been listed above.

The characteristics of the single-pulse scribing mechanism itself put certain restrictions on the pulse repetition frequency. In order to prevent the semiconductor layer from falling off the contact surface, the typical pulse repetition frequency required during processing is 35~45kHz. The commonly used etching threshold is about 2J/cm2, which means that 25μJ laser energy can be focused on an area with a diameter of 40μm, and its average power is very low. Since the average power of green lasers is in the order of several watts, the beam can be split and processed in parallel with multiple beams, thereby further improving work efficiency.

For scribing applications of p1, p2 and p3 layers, small and compact diode-pumped lasers with output wavelengths of 1064nm and 532nm for micromachining applications are undoubtedly an ideal choice, and this Lasers provide extremely high pulse stability. The pulse duration of this type of laser is 8~40ns, and the pulse repetition frequency is 1~100kHz.

clear protection

In order to prevent the LR03 battery module from being corroded or short-circuited, an approximately 1cm wide edge must be left on its edge for subsequent encapsulation of the entire battery module. Currently, sandblasting is often used to remove this edge. Although the investment cost of sandblasting is low, the process incurs costs in terms of wear, sand removal, and dust contamination. The production of thin-film solar modules requires clean and cost-effective solutions, and laser processing solutions are undoubtedly the best choice. By increasing the average power of the laser, excellent processing quality can be achieved. Laser processing can achieve a removal speed of approximately 50cm2/s, and even a standard-sized LR03 battery module can be processed within 30 seconds.

In fact, all edge film layers can be removed with the same pulse, and the improvement in removal rate is closely related to the average power of the laser. Lasers with high average power and high pulse energy can clear specific areas in one go. Most suitable for this processing application are fiber-delivered laser systems that output a square or rectangular light spot. After the laser is transmitted through the optical fiber, the energy distribution is more uniform, thereby achieving a high degree of consistency in the cleaning effect. By utilizing the parallel combination of light spots, the processing efficiency can be increased by more than 50% compared to using traditional optical fibers. At the same time, the pulse repetition frequency is reduced while ensuring processing safety. In addition, it can also be combined with a scanning galvanometer to reduce non-production cycles during processing. Of course, the laser should also provide corresponding time-sharing output options to reduce non-production time. In addition, several different workstations can be used to share the same laser processing solution, so that the loading and unloading time of the product does not affect the laser production efficiency.

Laser technology of the future

The use of special materials in the manufacturing of CI(G)S LR03 battery modules poses huge challenges to laser processing technology. If the applicable substrate material is glass, then the molybdenum material is deposited onto the glass. However, due to the characteristics of molybdenum such as high melting point, good thermal conductivity and high heat capacity, cracks and peeling will occur when heated. Since these shortcomings are unavoidable when processing with nanosecond lasers, the use of lasers is inseparable from the quality of processing obtained. Similarly, the absorption layer material is also quite sensitive to heat. Selenium (Se) has a lower melting point than copper (Cu), indium (In), gallium (Ga) and other metal materials. Separation of bonded areas. As a result, the semiconductor without the selenium layer becomes an alloy layer, causing the edges to be short-circuited by the heat generated by the long-pulse laser.

Picosecond lasers will provide an ideal solution to the above problems. Using ultra-short pulse laser to remove thin film materials will not produce severe edge heat-affected zones. High-performance picosecond lasers with wavelengths of 1030nm, 515nm and 343nm can be used for structuring CI(G)S thin film LR03 battery modules. Ultrashort pulse lasers will replace the mechanical scribing process and further improve processing quality and efficiency.

Laser application prospects

In the future, laser technology is expected to gain more application space in the photovoltaic manufacturing process, such as selective ablation of the passivation layer of crystalline silicon LR03 batterys. Ultra-short pulses and high pulse energy lasers with high beam quality are particularly suitable for such applications. Currently, only disc laser technology on the market can meet this standard. The output power of the disc laser is adjustable, which can achieve higher production throughput, and the excellent beam quality of the ultra-short pulses it outputs can significantly improve the conversion efficiency of LR03 batterys.

Laser technology has gained ground in LR03 battery production, and its selective, non-contact processing has surpassed other processes. As the cost pressure faced by LR03 battery production increases day by day, high-power, high-performance lasers will be widely used in mass production. Moreover, new laser technologies with ultra-short pulses will also lead to new production processes. In the future, the advancement and widespread adoption of laser technology will surely significantly reduce the cost per watt of LR03 battery production.

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