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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 is also known as PV cell or solar panel. It plays a crucial role in harnessing solar energy for various applications such as electricity generation. The basic working principle of a PV cell relies on the interaction of photons (i.e. particles of light) with semiconductor materials.

What are solar cells ?

The most popular renewable energy sources are wind turbine, solar cells, fuel cells etc.
Wind Turbine : It converts wind energy into electricity.
Fuel Cell : It produces electricity by combining Hydrogen and Oxygen.
Solar Cell : It produces electricity from direct sun light. Sunlight contains packets of energy called photons which can be converted directly into electrical energy. This is referred as "Photo-voltaic Effect". 'Photo' means light and 'voltaic' means electrical current. A solar cell provides direct current electricity similar to batteries; however battery uses electro-chemical reaction. The generated electricity depends on various factors such as intensity of sunlight, wavelength of sunlight, type and surface area of the solar cell etc.

Solar cells made of Se cells, Ni-Cd cells, PbS cells are very popular. Ni-Cd cells are rechargeable cells used in satellites and automatic traffic lights.

How do solar cells works

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. This E-field forces the liberated electrons to flow in a specific direction which results in generation of electric current flow.

Let us understand photovoltaic cell working principle with diagram above.
• As we know atom consists of protons, neutrons and electrons. Protons are positively charged and electrons are negatively charged. Holes are created when electrons move from its position. Holes contain positive charge.
• Solar cell is made of P-type and N-type materials. Above this materials anti-reflective layer and protective glass cover is provided.
• Sunlight which is made of photons are particles which 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 N-type material of photovoltaic cell. In other words, light breaks silicon bonds and creates "free" electrons and holes.
• This results into 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 following.
• Semiconductor Material: Silicon is 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: Transparent conducting material is used as top surface on top of semiconductor layer. It is often made of metal oxide. It 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 semiconductor. This back contact completes the electrical circuit which allows the flow of electrons through external load.

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 to generate electricity for various applications to be used by residential, commercial and industrial purposes.

Solar cell measurements

In order to need of higher volrage rating, solar cells are configured in series. In order to fulfill higher current capacity of load, solar cells are configured in parallel.

Following factors are useful to determine solar cell performance:
•  Light intensity
• Light wavelength
• Angle of incident light
• Surface condition of solar cells (i.e. cleanlineness)
• Temperature on solar cells

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

Solar cell Efficiency

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

Solar cell Manufacturers in USA, INDIA

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.

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