A solar cell works on the photovoltaic principle and converts light energy into electricity. It uses the photovoltaic effect which is a physical and chemical phenomenon. As we dive into the detailed world of the construction and working of solar cell, we need to see the parts and functioning of the solar cell.
Individual solar cells are the main parts of photovoltaic modules. They are also known as solar panels. Solar cells are photovoltaic but their energy source is sunlight or artificial light. They are useful in producing energy and electromagnetic radiation and measuring light intensity.
Operating PV cells need three things:
- Excitons, absorption of light and plasmons and unbound electron-hole pairs
- Charge carrier separation
- Extraction of carriers to an external circuit
But to fully understand how each part works and what their contribution is to the overall functioning, we need to see the construction of the solar cells.
Solar Cell Construction
Let’s discuss the former amongst the construction and working of solar cells first. A solar cell is a junction diode. The construction of a solar cell varies from that of a standard p-n junction diode. First, a thin layer of p-type semiconductor comes in contact with a thick n-type semiconductor. Then, on the p-type semiconductor, the technician applies a few finer electrodes.
These fine electrodes do not create any obstruction in the pathway of the light to reach the thin p-n junction. A current-collecting electrode is also placed at the bottom of the n-type layer.
Another thing about the construction and working of solar cells is that the manufacturers encapsulate the assembly using thin glass. This helps to prevent mechanical shocks in the solar cell. You can place the encapsulated solar cells in an aluminium frame with a Tedlar back sheet.
Steps to Construction
Here are the steps to the construction and working of solar cells:
Build solar silicon cells that are either p-type or n-type, that is they are positively or negatively charged. P-type silicon cells are the traditional structures of solar cells. A p-type silicon cell depends on a positively charged base. This means that the bottom layer has boron and the top has a mixture of phosphorus.
However, the manufacturers build the n-type cell positively with the phosphorus serving as the base. The main difference lies in the fact that n-type cells offer more efficiency in the light-induced degradation that does not affect them.
Principle of Solar Cells
Solar cells have crystalline silicon that the manufacturers melt and mix with gallium or boron to form wafers. Then they add phosphorus to give silicon its electrical capability.
Then they cut the silicon ingot into thin sheets and an anti-reflective coating to capture the sunlight instead of reflecting it away from the panels. Next, they cut the thin lines into cells to capture and move the electrical current within the cell.
The solar cells become semiconductors of electricity which happens as a result of the photovoltaic effect. As it absorbs the sunlight’s photons, electrons drift within the solar cells to create energy.
Monocrystalline solar panels come from a single silicon fragment, whereas polycrystalline panels involve melting multiple silicon fragments together into a large sheet to create the silicon wafers present in the construction and working of solar cells.
Soldering solar cells together to form a panel, typically comprising 60 or 72 solar cells.
This step of the construction and working of solar cells sees the installation of the back sheet to protect the bottom of the solar cells.
Attaching a glass front, allows light to filter through to the solar cells and provides a protective layer.
Sealing a metal frame around the panel with silicon to fuse all layers.
Installing the junction box to safeguard the solar panel’s electrical wires from damage.
Testing the solar panel for quality and strength before shipping it out for use.
Following the quality testing, the solar panels are ready for shipping and installation in homes or for use in solar farms. Although the manufacturing process is generally similar for different types of solar panels, each type possesses its unique strengths.
Solar Cell Working Principle
How the Light Affects Solar Cells
When light reaches the p-n junction between p and n-type semiconductors, photons without problems penetrate the thin p-type layer.
These photons impart energy to the p-n junction, generating electron-hole pairs. This illumination or light disrupts the thermal equilibrium of the junction, prompting free electrons to migrate to the n-type facet.
On the other hand, the holes comply with a similar pattern closer to the p-type facet of the junction. Consequently, a potential barrier prevents free electrons at the n-kind facet from crossing the junction.
Simultaneously, this barrier potential obstructs the newly formed holes, resulting in an accumulation of electrons on one side (at the n-kind junction) and holes on the opposite. This orchestrated movement allows the p-n junction to function as a battery cell.
This is how the construction and working of solar cells take place.
How the Solar Cell Structure Reacts
Each solar cell comprises two slices of semiconductor material, often silicon, that undergo ‘doping’ with additional materials to impart either a positive or negative charge to each slice.
The top slice is typically doped with phosphorous to introduce electrons, creating a negative charge, while the bottom slice has boron added, resulting in fewer electrons and a positive charge. Metal conductive plates are incorporated on one side of each layer, and the junction between these layers is where the electric field is established.
When a photon of sunlight strikes the cell, it dislodges electrons from their atoms. These liberated electrons can then traverse between the conductors and move through the circuit, producing electricity.
What Kind of Current Does It Generate?
The construction and working of solar cell must also take into consideration the type of current it generates. The direct current (DC) electricity flows unidirectionally through the circuit, from the negative to the positive side.
However, to make it compatible with the Grid, home solar systems, or businesses, the current must pass through an inverter to convert it into alternating current (AC) electricity. AC power oscillates the flow direction periodically, pushing and pulling electrons.
The inverter not only facilitates this conversion but also provides system statistics and ground fault protection. The use of micro-inverters that optimise each solar panel in a system can enhance the overall output.
Once you understand the construction and working of solar cell, you can harness the Sun. It is one of the greenest and cleanest energy sources on the Earth. This functioning of the solar cells and panels is what makes solar power a fully sustainable and renewable energy resource.
FAQs: Comprehensive Guide to Construction and Working of Solar Cell
What is a solar PPA?
Solar PPA is a long-term financial deal. With a PPA, an investor or a homeowner does not have to pay for the upfront costs of the sole panels. Instead, they enter a third-party contract with solar panel providers or dealers who monitor the design, permitting and installation of the panels.
What happens to the electricity generated by solar cells?
Solar cells generate electricity in the form of Direct current. This flows from the negative side to the positive of the circuit. To make it compatible with the electrical grid, home systems, or businesses, the current passes through an inverter, converting it into alternating current (AC) electricity.
Why use inverters in solar power systems?
Inverters convert the DC electricity produced by solar cells into AC electricity. AC is necessary for most electrical applications. It allows easy integration of electricity into the existing electrical infrastructure, making it suitable for use in homes, businesses, and the broader power grid.
How do micro-inverters enhance solar panel performance?
Micro-inverters are devices that you can install on each solar panel in a system. They optimise the performance of individual panels, ensuring that solar array operates efficiently. This is particularly beneficial becаuse a single problematic panel, whether due to dirt or shade, does not negatively impact the overall output of the solar power system.
Understanding the construction and working of solar cell is crucial for harnessing solar power efficiently. Most of the materials in solar cells are of semiconducting nature.
The electricity generated is initially in the form of direct current, which is then converted to alternating current using inverters. Micro-inverters optimise individual panels for enhanced overall system performance.
Now, take a step towards sustainable energy by investing in renewable assets with SustVest. Embrace solar power to contribute to a greener and cleaner future. Act now for a brighter and sustainable tomorrow!
Founder of Sustvest
Hardik completed his B.Tech from BITS Pilani. Keeping the current global scenario, the growth of renewable energy in mind, and people looking for investment opportunities in mind he founded SustVest ( formerly, Solar Grid X ) in 2018. This venture led him to achieve the ‘Emerging Fintech Talent of the Year in MENA region ‘ in October 2019.