From its original laboratory applications to today's diverse fields of medicine, communications, manufacturing, military and scientific research, lasers have become an integral part of modern technology and science. The origins of lasers can be traced back to the mid-20th century, largely driven by the theoretical work of Arthur Schawlow and Charles Townes, along with the experimental work of Dexter R. Hansch (Theodore Maiman). The following is a more detailed account of the process by which the laser originated:
- Laying of theoretical foundations: In the early 20th century, Albert Einstein proposed the photon theory that light exists in the form of discrete particles (photons). This theory laid the foundation of quantum optics, which provided important support for the theoretical basis of the laser later.
- The theory of excited radiation: In 1951, Charles Towns and Arthur Lambert independently proposed the theory of excited radiation, which revealed that when atoms or molecules are in an excited state, they can be excited by a photon from an atom that has already been excited, thus producing photons with the same frequency and phase as the excited photon. The theoretical basis of this process became the core of how lasers work.
- Theoretical formulation of lasers: The theoretical work of Towns and Lambert triggered the study of how to realize excited radiation, and they developed the concept of light amplification using excited radiation. Their key idea was to gradually increase the number of photons by reflecting them back and forth in an optical cavity with high reflectivity, eventually forming a highly focused beam of light, the laser.
- Experimental Verification of Lasers 1: In 1958, American physicist Dexter R. Hansch succeeded in building the first working laser. He used a synthetic excitation medium, usually a mixture of nitrogen and neon, to achieve excited radiation. This laser produced a controlled, highly focused beam of light, which marked the official birth of laser technology.
It has been 63 years since July 1960, when the world's first operable ruby laser with a wavelength of 0.6943 microns was successfully made by Meyman at Hughes Research Laboratories in the United States. A series of characteristics such as laser's high degree of focusing, good monochromaticity, high energy density, long-distance propagation, non-contact and so on make it widely used. Laser is often referred to as "the star of tomorrow in the 21st century", "one of the important technologies of the 21st century", "the most accurate ruler, the fastest knife". This kind of name also reflects the important position and wide application of laser technology in contemporary society and science and technology. Laser technology plays a key role in many fields such as communication, medical treatment, manufacturing, scientific research, military, environmental monitoring, etc., and is therefore regarded as one of the most promising and influential technologies in the 21st century. Particularly in the photovoltaic industry, laser technology is spawning a series of innovations that are making the manufacture of solar cells more efficient, more reliable, and more environmentally friendly.
Today, let's delve into the brand new applications of lasers in the photovoltaic industry.
Laser Cutting: Laser Scribers
Laser cutting is an extremely precise process that is used to cut silicon solar cell wafers to the desired size. Its main principle is that a focused laser beam is directed onto the surface of the material to be cut. The photon energy is absorbed by the material, resulting in localized heating of the material. When the energy of the laser beam is high enough, it can heat the surface of the material to a temperature sufficient to initiate melting or evaporation. In the case of metallic materials, this is usually melting, while in the case of non-metallic materials, such as plastics or wood, this is usually evaporation. Solar cell wafers are usually large silicon wafers, and laser cutting allows them to be cut into smaller cells with high precision to meet the size requirements of solar panels. This not only improves productivity and cell quality, but also greatly reduces material waste and manufacturing costs. The high degree of focusing and control precision of the laser beam makes the cutting process more delicate and produces almost zero amount of waste. In addition laser cutting also has a diversity of material applicability, not only for silicon solar cell wafers, but also can be used for other types of solar cells, such as thin film solar cells, as well as other materials cutting, so it has a high degree of flexibility. The advantage of using laser cutting solar cell sheet is the use of non-contact processing, no stress, so the cutting edge is straight, will not damage the structure of the wafer, the electrical parameters are better than the traditional mechanical cutting method, both to improve the yield and reduce costs, the width of the slit is small, high precision, the laser power can be adjusted, you can control the thickness of the cut, so as to realize the thinning of solar cells. Laser cutting technology can be applied to large-area battery sheets for scribing and cutting, precisely controlling the cutting accuracy and thickness, further reducing cutting debris and improving battery utilization. In addition to the application of cutting on the battery sheet, there are also in the photovoltaic glass can also be scribed, the principle is the same.
Laser doping: laser doping equipment
Laser doping is a material processing technique usually applied to semiconductor materials, especially silicon, to change their electrical properties. The principle of the technique is to use a high-power laser to irradiate the semiconductor surface and introduce an external doping material (usually boron or phosphorus) into the semiconductor lattice. This process involves the energy of the laser heating the semiconductor material to a high enough temperature that the dopant material is able to penetrate the lattice and displace certain atoms of the semiconductor material, thereby altering the conductive properties of the material. The laser energy is utilized to drive boron atoms to diffuse within the silicon wafer to achieve a selective emitter SE structure. By heavily doping the metal grid line in the contact area with the silicon wafer and keeping light doping in other areas on the front side, it can not only form a good ohmic contact between the electrode and the emitter, but also reduce the complexation of oligons on the emitter surface (TOPCon technology route), which can obtain higher short-circuit current, open-circuit voltage, and fill factor, and improve the photoelectric conversion efficiency of the solar cell. Its advantages lie in 1, high precision: laser doping can achieve very high doping accuracy and spatial resolution, enabling precise control of the doping process.2, non-contact: non-contact processing methods do not introduce mechanical damage or impurity contamination, especially suitable for the manufacture of high-performance semiconductor devices.3, fast processing: laser doping is a high-speed process, which allows a large amount of material to be processed in a short period of time.4, Wide applicability: This technology is applicable to different types of semiconductor materials, including silicon, gallium gallium arsenide, indium arsenide, etc.. In the photovoltaic industry, laser doping technology is commonly used in the manufacture of solar cells to improve cell performance. Some leading photovoltaic companies and technology providers in the development and application of laser doping technology.
Overseas companies include: Applied Materials, Amtech Systems, etc.
Domestic companies include: Dier, Dazhou, Shengxiong, etc.
In terms of material modification, in addition to laser doping, there are laser-induced repair technology, laser-induced annealing technology, laser-induced sintering technology is a new technology released by Dier Laser Technology on August 14, 2023, which can gain 0.2% of the battery efficiency.
Laser transfer printing
Laser Pattern Transfer Printing (PTP) is a new type of non-contact printing technology, the principle of this technology is to coat the required paste on a specific flexible light-transparent material, using a high-power laser beam with high-speed graphic scanning, the paste is transferred from the flexible light-transparent material to the surface of the battery to form a grid line. Through non-contact laser printing technology (PTP) to improve high-efficiency solar cells fine grid printing process, can break through the traditional screen printing line width limit, easily realize the line width of 25um or less, in the cell wafers printed on a larger aspect ratio of ultra-fine grid lines, to help the battery to achieve ultra-fine grid cells, matching selective emitter technology, to enhance the efficiency of the solar cell at the same time, a substantial savings of paste consumption 20% or more, and ultimately reduce the cost of battery production and power generation. The principle of laser transfer technology is based on the high energy density and precise control of laser. Its main steps include: 1, the bottom layer preparation: in the manufacturing process of solar cells, the bottom layer is usually a transparent conductive layer, used to collect solar energy and transmission of electric current. 2, laser irradiation: the use of laser beam irradiation on the bottom layer, to move the laser focus in a precisely controlled manner. The high energy density of the laser selectively sinter or scratch the underlying layer to form a specific pattern for the cell.3. Layer Stacking: Different cell layers, such as the active layer and the electrodes, can be stacked on top of the underlying layer layer layer-by-layer by laser transfer.4. Molding and Encapsulation: Finally, the cell module is processed through molding and encapsulation steps to form the final solar cell. Its advantages are: 1, high precision: laser transfer technology can achieve very high precision and resolution, helping to produce high-efficiency solar cells, printing highly consistent, excellent uniformity, error in 2um, low temperature silver paste is also applicable (HJT). 2, non-contact: this is a non-contact processing method, will not damage or contaminate the battery components, to help improve the quality of the cell, and in the The future process of thin film is certainly sharp. 3, fast production: laser transfer printing is a high-speed processing methods, can improve the production efficiency of solar cells. 4, multi-material adaptability: this technology can be applied to a variety of different types of battery materials, including organic materials, silicon materials, etc. 5, cost control: compared with the screen printing, laser transfer printing of the grid is finer, can be done below 18um Paste savings of 30%, TOPCON's double-sided silver paste, HJT low-temperature silver paste will be due to laser transfer technology to reduce the consumption of a large number of silver paste has become one of the important technologies to reduce costs and increase efficiency.
Laser perforation
The principle of laser perforation is to use the high energy density of the laser beam to heat the local area of the material to a high enough temperature to evaporate, melt or vaporize the material to form holes. The key to laser perforation is controlling the laser's energy density, exposure time, and focus position to ensure that the material is precisely machined into the desired hole. This precision and high energy density make laser drilling ideal for many industrial applications, including solar cell manufacturing in the photovoltaic industry. Different types of lasers (e.g., CO2 lasers, Nd:YAG lasers, femtosecond lasers, etc.) can be used for different types of materials and applications, so the appropriate laser system needs to be selected for the specific need. Laser perforation has a wide range of applications in the photovoltaic industry, especially in the solar cell manufacturing process. The following are some of the main applications of laser perforation in the photovoltaic industry:
- Cell processing: Laser perforation is commonly used in the processing of solar cells. These small holes can be used to improve the light absorption efficiency of the cell and reduce reflection losses, thus increasing the photoelectric conversion efficiency (the trapped light effect). Laser perforation allows precise and efficient processing of silicon wafers, polysilicon wafers and other solar cell materials.
- Cell and Module Connections: In the solar cell assembly process, wires are needed to connect cells to each other. Laser perforation can be used to create holes for connecting wires between cells to ensure smooth current transfer between cells and reduce energy loss. Laser perforation is also used to make holes and connection points for brackets, frames and other components in the manufacturing process of solar modules.
- Photovoltaic glass backsheet: Because conventional photovoltaic modules only use photovoltaic glass for the cover plate, while double-glass modules use photovoltaic glass for both the cover plate and the back plate, and the back plate photovoltaic glass must be punched in a specific location in order to bring the current leads from the photovoltaic module to the junction box. Therefore, the perforation of PV glass backsheets has become an essential process in the production of further processing.
Overall, laser perforation is widely used in the photovoltaic industry to improve the efficiency of solar cells, reduce manufacturing costs, and improve product quality. These applications help to promote the development of solar energy technology and promote the use of renewable energy. It should be noted that specific applications may vary depending on the manufacturing process and material, so the actual application needs to be based on the need to select the appropriate laser technology and parameters.
The above are just some of the applications of laser processes in the photovoltaic industry, which of course also include laser slotting (XBC), laser ablation (PERC) and so on.
Future Prospects:
As laser technology continues to advance, we can foresee more innovations that will further advance the PV industry. More efficient PV materials, smarter production processes, and more applications utilizing PV energy are likely to emerge in the future. New applications of laser technology in the PV industry have not only increased productivity, but also improved module performance and sustainability. Continued innovation in this technology will continue to drive the development of solar cells and contribute to a clean energy future. Additionally in photovoltaic manufacturing, laser technology not only improves productivity, but also reduces waste generation, which helps to minimize the burden on the environment. In addition, laser cleaning technology does not require chemicals, saving energy and resources. Clean technology for a clean industry - wonderful.
Finally, the depth of laser technology is all about understanding. The wonders of laser technology cannot be written enough.
