The hottest laser technology improves the manufact

2022-09-25
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Laser technology improves the manufacturing efficiency of thin-film solar cells

when the interval between the two chucks occurs, the conversion timer is an important tool for the production of thin-film solar cell modules, especially the high-performance ultrashort pulse laser, which can provide ultrashort pulses lasting only a few picoseconds, which can not only help manufacturers improve production, but also optimize processing technology

at present, photovoltaic energy as a renewable energy plays an important role in the discussion of solving the future energy problems. Technological progress is a crucial prerequisite for achieving parity consumption of electric energy, such as reducing the cost of photovoltaic power generation to close to the cost of traditional energy through technological progress

at present, crystalline silicon solar cells are the leading products in the photovoltaic market, and their conversion efficiency is the highest, with some manufacturers producing and processing oil cylinders as high as 20%. In the manufacturing process of crystalline silicon solar cells, lasers are mainly used for wafer cutting and edge insulation

only TIR value can be determined. In the process of laser edge insulation, the laser assisted doping process is used to prevent the power loss caused by the short circuit between the front and back of the battery. More and more lasers are used in laser assisted doping process to improve carrier mobility, especially for the contact fingers of electrodes. In the past few years, thin-film solar cells have made great progress, and industry experts hope that they can occupy about 20% of the market share in the photovoltaic market in the future

the film used in thin-film solar cells is only a few microns thick, so it can save a lot of materials in production. In the manufacturing process of thin-film solar cells, laser plays a decisive role. In the whole manufacturing process, the battery is structured and connected into modules by laser, and the modules are etched accordingly to ensure the required insulation performance

mature laser marking process

in the production process of amorphous silicon or cadmium telluride (CdTe) thin film solar cell modules, conductive films and photovoltaic films are deposited on large-area glass substrates. After each layer of film is deposited, laser is used to etch the film, and the batteries are automatically connected in series. In this way, the current of the battery and module can be set according to the battery width. Precise selective non-contact laser processing can be reliably integrated into the production line of thin-film solar cell modules. Generally speaking, the etching line is a continuous process of single laser pulse etching, and the spot size is 30~80 after the pulse is focused μ m. Therefore, in the P1 layer etching, the glass substrate should be etched by pulsed light with a pulse width of tens of nanoseconds (10~80ns)

transparent conductive oxides (TCO, such as ZnO and SnO2) are usually processed using near-infrared lasers and relatively high pulse repetition rates. Usually, the pulse repetition frequency needs to exceed 100kHz. A high pulse repetition rate ensures thorough cleaning of the incision

according to the difference of laser absorption coefficient of materials, it is necessary to select the appropriate laser wavelength for specific processing technology. The damage threshold of green laser to silicon is much lower than that of green laser to TCO, so green laser can safely pass through the TCO film and scribe the absorption layer. The marking mechanism of P2 layer and P3 layer is the same as that of P1 layer

the characteristics of the single pulse marking mechanism put forward certain restrictions on the pulse repetition rate. In order to prevent the semiconductor layer on the contact surface from falling off, the typical pulse repetition frequency required in the processing process is 35~45khz. The commonly used etching threshold is about 2j/cm2, that is, 25 μ The laser energy of J is focused to a diameter of 40 μ The average power of M is very low. Because the average power of green laser is in the order of several watts, it can split the beam and process multiple beams in parallel, so as to further improve the work efficiency

for the marking applications of P1, P2 and P3 layers, a compact diode pumped laser with output wavelengths of 1064nm and 532nm for micromachining applications is undoubtedly an ideal choice, and this laser can provide extremely high pulse stability. The pulse duration of this kind of laser is 8 ~ 40ns, and the pulse repetition rate is 1 ~ 100kHz

clear protection

in order to prevent the solar cell module from being corroded or short circuited, a 1cm wide edge must be left at its edge for the next packaging of the whole battery module. At present, sandblasting is often used to remove this edge. Although the investment cost of sand blasting method is low, this process will bring costs in terms of wear, sand removal and dust pollution prevention. The production of thin-film solar cell modules requires clean and affordable solutions, and laser processing is undoubtedly the best choice. By increasing the average power of laser, excellent processing quality can be obtained. Laser processing can achieve about 50cm2/s, including the removal speed determined by type evaluation and type approval. Even a standard size solar cell module can be processed within 30s

in fact, all the edge film layers can be removed with the same pulse, and the improvement of the removal rate is closely related to the average power of the laser. Laser with high average power and high pulse energy can clear specific areas at one time. The laser system with optical fiber transmission is the most suitable for this processing application, and its output square or rectangular spot. After the laser is transmitted through the optical fiber, the energy distribution is more uniform, so as to achieve a high degree of consistency in the removal effect. By using the parallel combination of light spots, the processing efficiency can be improved by more than 50% compared with the traditional optical fiber, and the pulse repetition frequency is reduced on the premise of ensuring the processing safety. In addition, it can also be combined with scanning galvanometer to reduce the non production cycle in the processing process. Of course, the laser should also provide corresponding time-sharing output options to reduce non production time. In addition, several different workstations can share the processing scheme of the same laser, so that the loading and unloading time of the product does not affect the production efficiency of the laser

future laser technology

the use of special materials in the manufacturing of CI (g) s solar cell modules poses a great challenge to laser processing technology. If the applicable base material is glass, molybdenum material is deposited on the glass. However, due to the high melting point, good thermal conductivity and high heat capacity of molybdenum, cracks and falling off will occur during heating. Because these shortcomings cannot be avoided when processing with nanosecond laser, the use of laser is inseparable from the processing quality. Similarly, the absorption layer material is also quite sensitive to heat. The melting point of selenium (SE) is lower than that of copper (Cu), indium (in), gallium (GA) and other metal materials. It can be separated from the bonding place at low temperature. As a result, semiconductors without selenium layers become alloy layers, resulting in short circuits at the edges by the heat generated by long pulse lasers

picosecond laser will provide an ideal solution to the above problems. Using ultrashort pulse laser to remove thin film materials will not produce serious edge heat affected zone. High performance picosecond lasers with wavelengths of 1030nm, 515nm and 343nm can be applied to the structure of CI (g) s thin film solar cell modules. Ultrashort pulse laser will replace the mechanical engraving process and further improve the processing quality and efficiency

laser application prospects

in the future, laser technology is expected to obtain more application space in the photovoltaic manufacturing process, such as the selective ablation of the passivation layer of crystalline silicon solar cells, and lasers with high beam quality and high pulse energy are particularly suitable for such applications. At present, only disc laser technology in the market can meet this standard. The output power of the disc laser is adjustable, which can achieve higher production, and the excellent beam quality of its output ultrashort pulses can significantly improve the conversion efficiency of solar cells

laser technology has won a place in the production of solar cells, and its selective and non-contact processing technology has surpassed other processes. With the increasing cost pressure of solar cell production, high-power and high-performance lasers will be widely used in large-scale production. Moreover, the new laser technology with ultrashort pulses will also bring new production processes. In the future, the progress and wide adoption of laser technology will greatly reduce the cost per watt of solar cell production. (end)

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