Photovoltaic (PV) Cell Working Principle

A photovoltaic (PV) solar cell is a semiconductor device that converts sunlight directly into electricity using the photovoltaic effect. It’s also known as a PV cell or solar panel and plays a crucial role in harnessing solar energy for various applications, like electricity generation. The basic working principle of a PV cell relies on the interaction of photons (particles of light) with semiconductor materials.

What are Solar Cells?

The most popular renewable energy sources are wind turbines, solar cells, and fuel cells.

• Wind Turbine: Converts wind energy into electricity.
• Fuel Cell: Produces electricity by combining Hydrogen and Oxygen.
• Solar Cell: Produces electricity from direct sunlight.

Sunlight contains packets of energy called photons which can be converted directly into electrical energy. This is referred to as the “Photo-voltaic Effect.” ‘Photo’ means light, and ‘voltaic’ means electrical current.

A solar cell provides direct current electricity, similar to batteries; however, a battery uses an electro-chemical reaction. The generated electricity depends on various factors such as the intensity of sunlight, wavelength of sunlight, type, and surface area of the solar cell. Solar cells made of Se cells, Ni-Cd cells, and PbS cells are very popular. Ni-Cd cells are rechargeable cells used in satellites and automatic traffic lights.

How do Solar Cells Work?

The semiconductor material used in most PV cells is typically made of silicon. Silicon atoms have four valence electrons. When these electrons are excited by incoming photons, they are freed to move around in the material. The PV cell’s structure includes a built-in electric field (E-field). This field forces the liberated electrons to flow in a specific direction, which results in the generation of electric current flow.

Let’s understand the photovoltaic cell’s working principle with the diagram above:

• As we know, an atom consists of protons, neutrons, and electrons. Protons are positively charged, and electrons are negatively charged. Holes are created when electrons move from their position. Holes contain positive charge.

• A solar cell is made of P-type and N-type materials. Above these materials, an anti-reflective layer and protective glass cover are provided.

• Sunlight, which is made of photons, are particles that contain energy.

• When light falls on the solar cell, these photons are absorbed by and consecutively pass through the material of the solar cell.

• The photons will excite the electrons found in the N-type material of the photovoltaic cell. In other words, light breaks silicon bonds and creates “free” electrons and holes.

• This results in the production of current (i.e., movement of holes). This movement of electrons or flow of current is known as “electricity”.

The key components of a typical photovoltaic solar cell include the following:

• Semiconductor Material: Silicon is the most commonly used material due to its abundance and appropriate electronic specifications. The other materials used in PV cells include gallium arsenide (GaAs), cadmium telluride (CdTe), copper indium gallium selenide (CIGS), etc.

• Front Contact: A transparent conducting material is used as the top surface on top of the semiconductor layer. It’s often made of metal oxide and allows sunlight to pass through while facilitating the collection of the generated electrons.

• Back Contact: A metal layer is placed at the bottom surface of the semiconductor. This back contact completes the electrical circuit, which allows the flow of electrons through an external load.

A solar panel or module consists of interconnected multiple PV cells. Further, these panels are combined in arrays to create solar power systems. These systems are capable of generating electricity for various applications to be used for residential, commercial, and industrial purposes.

Solar Cell Measurements

To achieve a higher voltage rating, solar cells are configured in series. To fulfill the higher current capacity of a load, solar cells are configured in parallel.

The following factors are useful to determine solar cell performance:

• Light intensity
• Light wavelength
• Angle of incident light
• Surface condition of solar cells (i.e., cleanliness)
• Temperature of the solar cells

The terminal voltage of the solar cell is measured using a Voltmeter or multimeter. Make the setup as shown in Figure-2 above. One can use either a voltmeter, power meter, or multimeter. To determine the I vs V curve, the resistance is varied from zero to the full resistance limit of the potentiometer. At each resistance within this range, voltage, current, and power are measured.

Solar Cell Efficiency

Solar cell efficiency is defined as the ratio of output to input. Output is the output power generated by the solar cell. Input is the incident flux density on the surface area of the solar cell.

Solar Cell Manufacturers in USA, INDIA

The following table mentions popular solar cell manufacturers:

Conclusion

The efficiency of PV cells has improved over the years, making solar energy an increasingly viable and environmentally friendly alternative to traditional fossil fuel-based energy sources. As technology continues to advance, the adoption of photovoltaic solar cells is expected to play a significant role in transitioning toward a more sustainable and clean energy future.