A photovoltaic (PV) cell, commonly known as a solar cell, is a semiconductor device that converts sunlight directly into electricity through the photovoltaic effect. Here's a step-by-step explanation of how this conversion process takes place:
Semiconductor Material: The PV cell is typically made of a semiconductor material, most commonly silicon. Silicon is abundant and has the necessary properties to efficiently convert sunlight into electricity.
Absorption of Photons: When sunlight (or photons) strikes the surface of the PV cell, it is absorbed by the semiconductor material. Photons are packets of energy that carry solar radiation.
Generation of Electron-Hole Pairs: The absorbed photons transfer their energy to electrons in the semiconductor atoms, causing them to become excited and break free from their atomic bonds. This creates electron-hole pairs. Electrons are negatively charged, while holes are positively charged.
Electric Field: The semiconductor material is intentionally doped (i.e., impurities are intentionally introduced) to create an electric field within the material. This electric field exists between the positively charged region (p-type) and the negatively charged region (n-type) of the cell.
Separation of Charges: Due to the electric field, the free electrons are pushed towards the n-type region, while the holes are pushed towards the p-type region. This separation of charges creates a potential difference between the two regions, generating an electric field across the PV cell.
Flow of Current: The separated electrons and holes create a flow of electrons from the n-type region to the p-type region, generating an electric current. This flow of electrons is what we know as electricity.
Metal Contacts: Metal contacts on the top and bottom of the PV cell allow the electrical current to be extracted and transferred to an external circuit for use in powering electrical devices or charging batteries.
Direct Current (DC) Output: The electricity generated by the PV cell is in the form of direct current (DC). This is the type of electricity used in small electronic devices and is also commonly used in off-grid solar systems.
Inverter (for AC Power): For grid-connected systems and most household electrical appliances, the direct current from the PV cell needs to be converted into alternating current (AC). This is achieved using an inverter, which changes the DC output into the standard AC used in the power grid and household devices.
It's worth noting that while a single photovoltaic cell can only generate a relatively small amount of electricity, multiple cells are interconnected to form a solar panel (also known as a PV module), and multiple panels can be combined to create larger solar arrays capable of generating significant amounts of electricity.