Question

Mechanism of photo conduction in a pv cell

Answer 1

Answer:

Conversion of light energy in electrical energy is based on a phenomenon called photovoltaic effect. When semiconductor materials are exposed to light, the some of the photons of light ray are absorbed by the semiconductor crystal which causes a significant number of free electrons in the crystal. This is the basic reason for producing electricity due to photovoltaic effect. Photovoltaic cell is the basic unit of the system where the photovoltaic effect is utilised to produce electricity from light energy. Silicon is the most widely used semiconductor material for constructing the photovoltaic cell. The silicon atom has four valence electrons. In a solid crystal, each silicon atom shares each of its four valence electrons with another nearest silicon atom hence creating covalent bonds between them. In this way, silicon crystal gets a tetrahedral lattice structure. While light ray strikes on any materials some portion of the light is reflected, some portion is transmitted through the materials and rest is absorbed by the materials.

Answer 2

The photovoltaic effect occurs when a photovoltaic cell is exposed to sunlight and generates a voltage or electric current in the cell.

• The p-n junction in these solar cells is made up of two types of semiconductors: p-type and n-type.
• Electrons flow to the positive p-side and holes flow to the negative n-side when these two types of semiconductors are coupled, generating an electric field.
• As a result of this field, negatively charged particles flow in one direction while positively charged particles flow in the opposite direction.
• Light is made up of photons, which are tiny bundles of electromagnetic radiation or energy.
• When photons of a certain wavelength collide with these cells, their energy is transferred to an electron in the conductive material, which causes the particle to jump to a higher energy level known as the conduction band.
• In their excited state in the conduction band, these electrons are free to flow through the material, and it is this motion that provides an electric current in the cell.