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Views: 16 Author: Site Editor Publish Time: 2024-10-22 Origin: Site
Solar energy is becoming an increasingly popular way to help homeowners reduce their energy bills and create a more self-sustaining home. When purchasing new solar panels, customers consider aspects such as power output, efficiency, aesthetics, and even solar cell technologies such as interconnecting back contact (IBC) or passivated emitter and rear contact (PERC), but few focus on the inner layers of the cells that make up an N- or P-type solar panel.
All of these aspects are quite important, but the choice between a photovoltaic (PV) module with P-type or N-type solar cells can have an impact on the performance and lifetime of the module. In this article, we will introduce you to the construction of these two types of solar cells, how they work, the differences and advantages of N-type and P-type solar panels, and other interesting details.
Inner structure of solar panels and how they work
A solar panel consists of several key layers working together to convert sunlight into electricity. The primary building block is the solar cell, usually made from silicon, a semiconductor material. Multiple solar cells are interconnected to form a module, and several modules make up a complete panel. When sunlight strikes the solar cells, it energizes electrons within the silicon material. In N-type cells, excess electrons move freely, while in P-type cells, the absence of electrons (or "holes") enables the flow of current. The movement of electrons creates a direct current (DC), which is then converted into alternating current (AC) by an inverter, making it usable for homes and businesses.
This photovoltaic process allows solar panels to harness clean, renewable energy, making them an essential component in the transition to sustainable power.
The materials and construction of solar cells vary slightly depending on their manufacturing technology. Traditional cells use an aluminum back surface field (Al-BSF), but there are newer technologies on the market, including PERC, IBC, and bifacial. With an understanding of conventional technologies, there is enough background knowledge to understand the differences between P-type and N-type solar cells.
Solar cells utilize a P-N junction structure, with P-type crystalline silicon (c-Si) wafers having extra holes (positively charged) and N-type crystalline silicon (c-Si) wafers having extra electrons (negatively charged). P-type wafers and N-type wafers are arranged in a different order, with a thinner upper layer being the emitter and a thicker lower layer being the main body region.
P-type crystalline silicon wafers are made by doping high-purity crystalline silicon with boron, a material with a low number of electrons that produces positively charged wafers. Similarly, N-type crystalline silicon wafers are doped with phosphorus, which is a material with more free electrons and therefore causes the wafers to be negatively charged. These layers are stacked to create an internal electric field. Aluminum-BSF solar cells feature an aluminum back surface field and full-area aluminum for the rear contacts, and silver paste-printed silver bars for the front contacts. The top of the emitter is also coated with a dielectric passivation layer to prevent corrosion of the cell's absorb layer.
Traditional crystalline silicon (c-Si) solar cells are made by doping silicon wafers with a variety of chemicals to facilitate the generation of electricity. The main difference between p-type and n-type solar cells is the number of electrons. P-type cells are usually doped with boron, which has one fewer 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).
The P-Type solar cells are first dosed with a layer of boron to create the cell’s base layer. With boron having 1 less electron than silicon, this creates a positively charged base. It is then dozed with phosphorus to create the cell’s top layer. With phosphorus having 1 more electron than silicon, a negative charge is created as the cell’s top layer, and electricity in this cell will flow from top to bottom.
In contrast, N-Type solar cells are first dozed with a layer of phosphorus, and with phosphorus having 1 more electron than silicon, a negative charge is created as the cell’s base layer. It is then dosed with boron to create the cell’s top layer. With boron having 1 less electron than silicon, a positive charge is created as the cell’s top layer, and electricity in this cell will flow from the bottom to the top.
N-type and P-type solar cells generate electricity through the photovoltaic effect. This process relies on the semiconducting properties of silicon, the main material of solar cells.
In N-type cells, phosphorus or arsenic atoms are added to silicon to provide additional electrons. These electrons can move freely through the material. When sunlight hits the cell, photons energize the free electrons, causing them to flow to the front surface and generate electricity.
The addition of boron atoms to P-type cells results in a lack of electrons or “holes” in the atomic structure. Boron accepts electrons from the neighboring N-type layer, forming a PN junction where electricity is generated. When sunlight comes in, electrons flow from the P-type layer to the holes in the N-type layer, creating an electric current (How Photovoltaic Cells Generate Electricity).
This process occurs in both types of cells, but due to the opposite doping of the semiconductor, the electrons flow in the opposite direction. The main difference is that free electrons move through the N-type layer, while electron holes move through the P-type layer.
N-type solar cells tend to have higher efficiency than P-type cells. According to research from Chint Global, N-type panels have an efficiency of around 25.7%, compared to 23.6% for P-type panels.
There are several reasons why N-type cells are more efficient:
N-type cells have a thinner emitter layer, which reduces recombination losses and allows more current to be collected.
N-type silicon has a higher electron mobility, allowing electrons to pass through the cell faster.
N-type cells are less susceptible to light-induced degradation and can maintain high efficiency over time.
The efficiency of P-type cells is limited by a thicker substrate layer, which absorbs more sunlight but also leads to more recombination. However, backside passivation and improvements in advanced cell structures can help improve the efficiency of P-type cells.
One of the main differences between N-type and P-type solar cells is how their efficiency is affected by temperature. The efficiency of a solar cell decreases as the temperature increases. The rate at which efficiency decreases is measured by the temperature coefficient.
N-type solar cells have a low temperature coefficient, typically around -0.30%/°C, while P-type cells have a temperature coefficient of around -0.50%/°C. This means that N-type cells maintain high efficiency at high temperatures.
According to the study, the production cost of P-type solar cells is about 0.081 €/watt, while the production cost of N-type cells is about 0.088 €/watt. P-type cells are simpler to produce, and therefore cheaper to manufacture on a large scale.
N-type cells require additional processing steps, such as making a thin emitter layer, which increases production costs. The specialized equipment required also adds to the cost. Although N-Type battery technology continues to advance, it still lags behind P-Type batteries in terms of manufacturability.
As a result, P-Type solar panels are often a more budget-friendly option for homeowners and businesses that are simply considering the upfront system cost. However, the increased efficiency and performance of N-Type panels can lead to greater long-term energy savings that can offset the higher initial investment over time.
P-Type solar cells tend to be easier to manufacture than N-Type cells. The production process for P-Type cells is very mature and has been optimized over decades of solar production. As a result, P-type cells are cheaper to produce on a large scale than the newer N-type technology.
According to Solar Magine, the additional steps required to manufacture N-cells result in higher production costs. In addition, the supply of N cells is lower because fewer manufacturers have switched to this newer technology.
P-type cells have dominated the solar industry since its inception. As a result, they are widely available from most panel manufacturers. N-type solar panels are harder to source and generally only produced by a handful of manufacturers that have invested in the newer production methods.
P-type solar cells tend to degrade faster than N-type cells. This is primarily due to light-induced degradation (LID) in P-type cells.
LID occurs when sunlight exposure causes defects in the crystalline structure of the silicon used in P-Type cells, and over time, these defects reduce the power output of the cells. According to the National Renewable Energy Laboratory, LID can cause P-type cells to lose up to 3 percent of their power within the first few hours of sunlight exposure. In contrast, N-type solar cells are not affected by LID.
Another degradation mechanism that affects P-type cells more than N-type cells is Potential Induced Degradation (PID). PID occurs when stray currents in the panel cause ions to move and increase the leakage current, which also reduces power output over time. N-type solar cells have proven to be more resistant to PID.
Because N-Type solar panels are more resistant to LIDs and more resistant to PIDs, N-Type panels last longer and lose power output more slowly than P-Type panels.
N-type solar panels utilize N-type silicon wafers as their raw material and are manufactured using various techniques, including TOPCon (Tunnel Oxide Passivated Contact), HJT (Heterojunction with Intrinsic Thin layer), PERT/PERL (Passivated Emitter Rear Totally Diffused/Passivated Emitter Rear Locally Diffused), IBC (Interdigitated Back Contact), and so on. The bulk c-si region of an N-type solar panel is negatively charged due to phosphorus doping of the wafer. Its top emitter layer is negatively charged due to boron doping.
P-type solar panels use P-type silicon wafers as their raw material and are primarily manufactured using traditional Al-BSF (Aluminum Back Surface Field) technology and PERC (Passivated Emitter Rear Contact) technology. P-type solar panels have a prominent bulk c-si 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 marketplace.
N-type and P-type solar panels are becoming popular choices for homeowners across the country. It's important to understand the differences in their performance, durability, efficiency, and cost-effectiveness to help you make a more informed decision about which solar panels are best for your solar system.
In terms of performance and efficiency, N-Type solar panels do have a slight edge over P-Type solar panels, with N-Type solar panels having an efficiency level of 25.7% compared to P-Type panels' 23.6%.
When comparing overall lifespan, n-type solar panels do have a longer lifespan than p-type solar panels due to their construction. However, in terms of price, p-Type solar panels are more favorable than n-Type solar panels. Of course, when calculating the cost, we not only have to consider the price of a solar panel of the same area, but also the limitations of the available space and the expected lifespan.
To further explain these, we have compared N-type vs. P-type solar panels in the table below.
| N-Type Solar Panel | P-Type Solar Panel | |
|---|---|---|
LID Due to Manufacturing Defects | No LID caused by manufacturing defects | Up to 10% performance reduction caused by LID due to boron-oxygen defect |
Solar Panel Efficiency | 25.7% | 23.6% |
Manufacturing Cost | Slightly higher production cost | Standard cost |
Product Warranty | 20 years warranty | 12 years warranty |
Power Degradation Warranty | 30 years warranty | 25 years warranty |
The main advantage of N-Type solar panels over P-Type panels is the absence of boron oxygen defects, which can degrade module performance by up to 10% in just a few weeks, caused by LID. N-Type solar panels, on the other hand, are not affected by this phenomenon and only experience periodic degradation after a few years.
Since holes are minority carriers in the bulk of the N-type solar panel, there is less window for the recombination process to occur, resulting in a higher efficiency of the module. Currently, the efficiency of N-type solar panels has reached 25.7% and is likely to continue to improve, while the efficiency of P-type solar panels is only 23.6%.
Manufacturing cost is one of the few drawbacks of N-Type solar panels.P-Type solar panels are a highly developed technology that is ripe for large-scale manufacturing, which reduces the cost.The manufacturing process for N-Type solar panels is very similar to that of P-Type panels, but there are a number of different steps in the manufacturing process that result in the higher cost of these components.
Last but not least, the warranty for N-type solar panels truly proves that the technology is better and can be backed up for a longer time by the manufacturer. These modules feature a 20-year warranty for the product and a 30-year warranty for the performance, while many P-type solar panels are only backed with a 12-year warranty for the product and a 25-year warranty for the performance.
Although breaking down the pros and cons for the panel types can be an easy solution for determining a better solar panel design, it is also important to consider the location and environment the solar panels will be used in. This can be a main determining factor in choosing the best panel type for your investment.
N-Type Panels: These typically have higher efficiency ratings, often exceeding 20%. They perform better in low-light and shaded conditions, making them ideal for areas with variable sunlight.
P-Type Panels: While still efficient, P-Type panels usually range from 15% to 19%. Their efficiency can drop significantly in less-than-ideal conditions, which may lead to lower energy output.
Initial Investment: P-Type panels are generally more affordable upfront, which can make them attractive for those on a budget. However, remember to factor in potential performance differences.
Long-Term Savings: Although N-Type panels have a higher initial cost, their greater efficiency and lower degradation rates can lead to substantial energy savings over time. Consider the overall return on investment.
N-Type Panels: Known for their resilience, N-Type panels are less affected by temperature changes and humidity. They tend to degrade more slowly, which can be crucial in areas with extreme weather.
P-Type Panels: While still durable, P-Type panels may experience greater performance loss in harsh conditions. If your region has frequent temperature swings or humidity, N-Type could be the better option.
Both N-Type and P-Type panels generally have a lifespan of 25-30 years. However, N-Type panels often maintain their efficiency longer, making them a wise investment for long-term use. Check the manufacturer’s warranty for specifics.
P-Type Panels: More widely produced and commonly available, these panels are easier to source, which can be a significant factor in your decision.
N-Type Panels: While gaining popularity, N-Type panels may not be as readily available in all markets. Ensure that you can find reliable suppliers for your installation needs.
Manufacturing: The production processes for both types can have environmental implications. N-Type panels may require less energy to manufacture despite their higher upfront costs. Investigate the sustainability practices of manufacturers.
Recycling: Both panel types are recyclable, but the processes may differ. N-Type panels are often easier to recycle due to their simpler composition, which could influence your decision if environmental considerations are important to you.
The installation process can vary based on the type of panel. N-Type panels may require specific mounting systems or configurations, while P-Type panels might be more straightforward to install. Consulting a professional installer can provide clarity on any unique requirements.
Look for robust warranties that reflect the manufacturer's confidence in their products. N-Type panels may come with longer warranties due to their expected longevity. Ensure you understand the terms and what they cover.
Consider your local climate. N-Type panels tend to perform better in cooler and shaded environments, while P-Type panels might be more effective in consistently sunny areas.
Depending on the design and color of the panels, some consumers might prefer one type over the other for aesthetic reasons. N-Type panels can sometimes be more visually appealing due to advancements in design.
When you're starting to choose components for a new solar system, you need to consider the following factors to determine which solar panel is right for you: budget, energy needs, and available installation space.
N-type solar panels have a higher upfront cost, but they are more efficient and can generate more energy. P-type solar panels have a lower upfront cost, but they are less efficient.
If you have a smaller available installation space but high energy needs, N-type solar panels may be a better choice. If you have a larger available installation space and a limited budget, P-type solar panels may be a better choice.
N-type and P-type solar cells have their own advantages and disadvantages. N-type solar cells are more efficient and have a longer lifespan, but they are more expensive. P-type solar cells are less expensive and are more resistant to radiation, but they are susceptible to light-induced degradation and have a shorter lifespan than N-type solar cells. When choosing a solar panel, you need to consider your specific needs and circumstances.
