The photochemical reaction in a photovoltaic PV cell, also known as a solar cell, works to generate electricity through the photovoltaic effect. The photovoltaic effect is a process in which light photons striking a semiconductor material generates a flow of electrons, creating an electric current. Here's a step-by-step explanation of how this process works:1. Absorption of light: When sunlight composed of photons strikes the surface of a PV cell, some photons are absorbed by the semiconductor material, usually silicon, which is the most commonly used material in PV cells.2. Generation of electron-hole pairs: The absorbed photons transfer their energy to the electrons in the semiconductor material. This added energy excites the electrons, causing them to break free from their atoms, leaving behind positively charged "holes." The result is the creation of electron-hole pairs.3. Separation of charge carriers: The PV cell is designed with an electric field, typically created by doping the silicon with specific impurities to form a p-n junction p-type and n-type layers . This electric field separates the negatively charged electrons from the positively charged holes, preventing them from recombining.4. Collection of charge carriers: The separated electrons and holes move towards their respective charge-collecting layers the n-type layer collects electrons, and the p-type layer collects holes . Metal contacts on the top and bottom of the cell allow the electrons to flow out of the cell, creating an electric current.5. Conversion to electricity: The electric current generated by the PV cell can then be used to power electrical devices or sent to the power grid.The efficiency of a PV cell in converting sunlight to electricity depends on the properties of the materials used. Some key properties that make materials efficient for this purpose include:1. Bandgap: The semiconductor material should have an appropriate bandgap, which is the energy difference between the valence band where electrons are bound to atoms and the conduction band where electrons can move freely . A suitable bandgap allows the material to absorb a significant portion of the solar spectrum and generate a useful voltage.2. Charge carrier mobility: High charge carrier mobility enables the electrons and holes to move quickly through the material, reducing the chance of recombination and increasing the efficiency of the cell.3. Absorption coefficient: A high absorption coefficient means that the material can absorb a large amount of sunlight, generating more electron-hole pairs and thus more electricity.4. Stability: The material should be stable under the operating conditions of a PV cell, including exposure to sunlight, heat, and humidity, to maintain its performance over time.5. Cost-effectiveness: The material should be relatively inexpensive and abundant to make the production of PV cells economically viable.Silicon is the most widely used material in PV cells due to its suitable bandgap, high charge carrier mobility, and abundance. However, researchers are continually exploring new materials, such as perovskites and organic semiconductors, to improve the efficiency and cost-effectiveness of solar cells.