Introduction to photovoltaic modules
(monocrystalline silicon, N-type, half-cell, shingled, heterojunction, PERC, TOPCon)
Photovoltaic modules, also known as solar panels, are the most important components in solar power generation systems. A complete photovoltaic module is composed of dozens of solar cells, junction boxes and frames. Since single solar cells cannot be used directly as power sources, if you want to use them as power sources, you must connect several single cells in series and parallel and tightly seal them into modules.
The principle of solar power generation, sunlight shines on the semiconductor p-n junction of the photovoltaic cell to form new hole-electron pairs. Under the action of the p-n junction electric field, holes flow from the p region to the n region, and electrons flow from the n region to the p region. When the circuit is connected, current is formed. Its function is to convert solar energy into electrical energy and send it to the battery for storage, or to drive the load to work.
Three types of solar cell technologies
1. Crystalline silicon solar cell technology, there are differences between monocrystalline silicon and polycrystalline silicon. The advantage is that the photoelectric conversion rate is high, which can reach more than 21%. The disadvantage is that the price is relatively expensive. Crystalline silicon solar cell technology is the mainstream technology in the current market.
2. Thin-film solar cell technology has the advantages of less material consumption and lower price. The major disadvantage is that the photoelectric conversion rate is only half of that of crystalline silicon, but the conversion efficiency is only 6%-10%, so the market share has always been very low.
3. New solar cell technology has the advantages of high conversion rate and low cost. Perovskite photovoltaic cells are a new type of solar cell product that is expected to be mass-produced the fastest. The theoretical efficiency limit of single-junction perovskite cells can reach 33%, which is higher than that of crystalline silicon cells and thin-film cells. However, the biggest disadvantage of perovskite photovoltaic cells is that the efficiency attenuation is relatively serious. Before the efficiency attenuation technology is solved, it will not be used on a large scale for the time being.
Polycrystalline silicon photovoltaic modules and monocrystalline silicon solar modules
1. Polycrystalline silicon photovoltaic modules: photovoltaic modules processed from polycrystalline silicon wafers. Polycrystalline silicon is made of polycrystalline silicon block materials using ingot casting technology (square silicon ingots).
2. Monocrystalline silicon photovoltaic modules: photovoltaic modules processed from monocrystalline silicon wafers. Monocrystalline silicon is made from polycrystalline silicon block materials using a rod drawing process (round silicon rods).
P-type photovoltaic modules and N-type photovoltaic modules
1. P-type photovoltaic modules: photovoltaic modules assembled using P-type solar cells. P-type solar cells are silicon wafers into which the trivalent element “boron” is infiltrated during the cell doping process, and the element “gallium” can also be added. The conversion rate of P-type cells in mass production of photovoltaic modules in 2023 is about 21.1% to 21.5%.
2. N-type photovoltaic modules: photovoltaic modules assembled using N-type solar cells. N-type solar cells are silicon wafers into which the pentavalent element “phosphorus” is infiltrated during the cell doping process, and the element “arsenic” can also be added. The conversion rate of N-type cells in mass production of photovoltaic modules in 2023 is about 22.1% to 22.5%.
Types of photovoltaic module structure processes
1. Half-cell structure process: a cell is cut into two pieces and then assembled into a photovoltaic module.
2. Shingled structure process: Cut a cell into five to six long strips, and then use conductive glue to overlap the edges of multiple small cells to assemble into photovoltaic modules.
3. Flexible module process: Flexible modules are also called lightweight modules. Photovoltaic modules can be bent and are particularly suitable for installation on curved roofs. One solution is to use flexible panels instead of glass panels based on the shingled photovoltaic module process. Another solution is to use thin-film batteries to make flexible photovoltaic modules.
Solar cell size classification
182 size and 210 size cell introduction
1. 182 photovoltaic module lineup manufacturers: that is, photovoltaic modules with a single cell size of 182 (182mm*182mm).
2. 210 photovoltaic module lineup manufacturers: that is, photovoltaic modules with a single cell size of 210 (210mm*210mm).
Introduction to rectangular photovoltaic module size and cells
After several size changes, the development of mainstream sizes has become more intense and diversified. In 2019, with the introduction of large-size silicon wafers, their advantages in reducing costs enabled them to quickly penetrate the market. As a result, the demand for M6 (166*166 mm) and smaller sizes declined rapidly, with only 2% of the market share remaining in 2023.
From 2022, M10 (182*182mm) and G12 (210*210mm) sizes gradually became mainstream, but each component factory continued to introduce rectangular silicon wafer sizes that integrated component layouts, including 182.2*183.5mm, 182.2*183.75mm, 182.2*185.3mm, 182.2*186.8mm, 182.2*188mm, 182.2*191.6mm, 182.2*199mm, 182.2*210mm, to enhance product competitiveness. The diversity of silicon wafer sizes has brought confusion and inconvenience to the industry. Customized silicon wafer sizes have brought challenges to the purchasing and sales and supply chain management capabilities of non-vertically integrated manufacturers; for end users, the excessive module sizes on the market have also brought challenges to their design and management.
According to the initiative, manufacturers can produce standard modules within the range of 182mm and 210mm silicon wafers to meet customer needs, and determine that future 66-cell, 72-cell, 2382*1134mm modules will adopt 182.2*191.6mm or 182.2*210mm sizes.
N-Type VS. P-Type Solar Cells: Which One Is Better?
The fundamental difference between N-type and P-type solar cells
A standard crystalline silicon (c-Si) solar cell is a silicon wafer doped with various chemicals to promote power output. The fundamental difference between P-type and N-type solar cells is the number of electrons. P-type cells usually dope the silicon wafer with boron, which has one less electron than silicon (making the cell positively charged). N-type cells are doped with phosphorus, which has one more electron than silicon (making the cell negatively charged).
What are N-type and P-type solar panels?
N-type solar cells
N-type solar cells use N-type silicon wafers as raw materials and are manufactured using a variety of technologies, including TOPCon (tunnel oxide passivation contact), HJT (intrinsic thin layer heterojunction), PERT/PERL (passivated emitter back fully diffused/passivated emitter back locally diffused), IBC (interleaved back contact), etc. Due to the phosphorus doping in the wafer, the bulk silicon area of N-type solar panels is negatively charged. Due to the boron doping, its top emitter layer is negatively charged.
P-type solar cells
P-type solar cells use P-type silicon wafers as raw materials and are mainly manufactured using traditional Al-BSF (aluminum back surface field) technology and PERC (passivated emitter back contact) technology. P-type solar panels have a significant bulk silicon area that is negatively charged due to boron doping. Its top emitter layer is positively charged due to phosphorus doping. PERC is more commonly used in the market.
N-Type VS. P-Type Solar Cells Technology Route
P-Type Cell Technology Route
1. BSF technology is aluminum back field cell, aluminum back field passivation technology, the conversion efficiency is less than 20%, in 2015, it was the mainstream cell technology in the photovoltaic industry, occupying 90% of the market, and now it is basically eliminated due to the low conversion rate.
2. PERC technology is emitter passivation and back contact technology. The conversion efficiency is about 23%. It is the mainstream technology now, with the highest market share. Basically, most P-type photovoltaic modules use PERC technology, and the actual conversion rate is more than 21%. In 2020, PERC cells accounted for more than 85% of the global market, and currently bifacial PERC is the main one.
N-Type Cell Technology Route
1. IBC full back electrode contact cell, the conversion efficiency of IBC cells has been steadily increasing year by year, the average conversion efficiency of mass-produced cells is 24.5%, and the theoretical conversion efficiency limit is 26.2%.
2. HJT heterojunction cell, intrinsic thin film heterojunction cell technology, the basic principle is to use crystalline silicon solar cells as the base layer and then superimpose thin film solar technology. The general classification still belongs to the N-type component technology route. There are two types of heterojunction cells, HJT and HIT. The average conversion efficiency of the cell mass production is 24.73%, and the theoretical conversion efficiency upper limit is 27.5%.
3. TNC passivated contact cell, the current TNC cell mass production conversion efficiency has exceeded 25.1%
4. TOPCon oxide passivated contact cell technology, the highest mass production efficiency exceeds 25%, and the theoretical conversion efficiency upper limit is 28.7%. TOPCon cell is a tunnel oxide passivated contact solar cell (Tunnel Oxide Passivated Contact solar cell), which was proposed by the German Fraunhofer Institute for Solar Energy in 2013. Due to its excellent passivation contact effect, its theoretical limit efficiency is as high as 28.7%, higher than 24.5% PERC and 27.5% HJT, but not as good as BC.
Which one has better development prospects, P-type or N-type photovoltaic modules?
1. The theoretical limit efficiency of N-type TOPCon cells is 28.7%. The conversion rate of mass-produced N-type photovoltaic modules in the market is about 22.1% to 22.5%. There is still a lot of room for improvement in subsequent technologies.
2. The theoretical limit efficiency of P-type PERC cells is 24.5%. The conversion rate of mass-produced P-type photovoltaic modules is about 21.1% to 21.5%. The technical development space is close to the bottleneck, and there is very little room for subsequent technical improvement.
3. According to the latest investment and technology trends of various cell manufacturers, P-type basically only specializes in PERC technology, while N-type has four or five cell technologies in progress. Although N-type photovoltaic modules have low production and high prices now, in the long run, N-type will have a higher market share than P-type photovoltaic modules. It is expected that N-type photovoltaic modules will become the mainstream photovoltaic module product after 2025.
N-type or P-type solar panels, which one should we choose?
When choosing components for your new solar system, you must first determine whether N-type or P-type solar panels are suitable for you. When choosing between P-type and N-type solar panels, consider your budget, energy needs, and available installation space.
In terms of installation cost, N-type solar panels are more expensive than P-type solar panels. In terms of energy demand, N-type solar panels are able to generate more energy than P-type solar panels due to their higher efficiency.
Conclusion
As the market demand for battery conversion efficiency continues to grow, photovoltaic manufacturers have begun to create the next generation of battery technology with higher conversion efficiency limits – N-type high-efficiency batteries. N-type batteries are represented by TOPCon, HJT, and IBC. They have the advantages of high conversion efficiency, anti-attenuation, low temperature coefficient, and high bifaciality, which are conducive to improving photovoltaic power generation gain and reducing the cost per kilowatt-hour. They have broad development prospects.
