- Solar Cell Definition: A solar cell (also known as a photovoltaic cell) is an electrical device that transforms light energy directly into electrical energy using the photovoltaic effect.
- Working Principle: The working of solar cells involves light photons creating electron-hole pairs at the p-n junction, generating a voltage capable of driving a current across a connected load.
- Construction Details: Solar cells consist of a thin p-type semiconductor layer atop a thicker n-type layer, with electrodes that allow light penetration and energy capture.
- Material Characteristics: Essential materials for solar cells must have a band gap close to 1.5 ev, high optical absorption, and electrical conductivity, with silicon being the most commonly used.
- Practical Uses: Solar cells power devices from small calculators and wristwatches to large-scale applications in spacecraft, highlighting their versatility and growing importance in renewable energy systems.
What is a Solar Cell?
A solar cell (also known as a photovoltaic cell or PV cell) is defined as an electrical device that converts light energy into electrical energy through the photovoltaic effect. A solar cell is basically a p-n junction diode. Solar cells are a form of photoelectric cell, defined as a device whose electrical characteristics – such as current, voltage, or resistance – vary when exposed to light.
Individual solar cells can be combined to form modules commonly known as solar panels. The common single junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts. By itself this isn’t much – but remember these solar cells are tiny. When combined into a large solar panel, considerable amounts of renewable energy can be generated.
Construction of Solar Cell
A solar cell functions similarly to a junction diode, but its construction differs slightly from typical p-n junction diodes. A very thin layer of p-type semiconductor is grown on a relatively thicker n-type semiconductor. We then apply a few finer electrodes on the top of the p-type semiconductor layer.
These electrodes do not obstruct light to reach the thin p-type layer. Just below the p-type layer there is a p-n junction. We also provide a current collecting electrode at the bottom of the n-type layer. We encapsulate the entire assembly by thin glass to protect the solar cell from any mechanical shock.
Working Principle of Solar Cell
When light photons reach the p-n junction through the thin p-type layer, they supply enough energy to create multiple electron-hole pairs, initiating the conversion process. The incident light breaks the thermal equilibrium condition of the junction. The free electrons in the depletion region can quickly come to the n-type side of the junction.
Similarly, the holes in the depletion can quickly come to the p-type side of the junction. Once, the newly created free electrons come to the n-type side, cannot further cross the junction because of barrier potential of the junction.
Once the newly created holes reach the p-type side, they cannot cross back over the junction due to the barrier potential. This separation of electrons and holes across the p-n junction allows it to function like a small battery cell.
A voltage is set up which is known as photo voltage. If we connect a small load across the junction, there will be a tiny current flowing through it.
V-I Characteristics of a Photovoltaic Cell
Materials Used in Solar Cell
Materials used in solar cells must possess a band gap close to 1.5 ev to optimize light absorption and electrical efficiency. Commonly used materials are-
- Silicon.
- GaAs.
- CdTe.
- CuInSe2
Criteria for Materials to be Used in Solar Cell
- Must have band gap from 1ev to 1.8ev.
- It must have high optical absorption.
- It must have high electrical conductivity.
- The raw material must be available in abundance and the cost of the material must be low.
Advantages of Solar Cell
- No pollution associated with it.
- It must last for a long time.
- No maintenance cost.
Disadvantages of Solar Cell
- It has high cost of installation.
- It has low efficiency.
- During cloudy day, the energy cannot be produced and also at night we will not get solar energy.
Uses of Solar Generation Systems
- It may be used to charge batteries.
- Used in light meters.
- It is used to power calculators and wrist watches.
- It can be used in spacecraft to provide electrical energy.
Conclusion: Though solar cell has some disadvantage associated it, but the disadvantages are expected to overcome as the technology advances, since the technology is advancing, the cost of solar plates, as well as the installation cost, will decrease down so that everybody can effort to install the system. Furthermore, the government is laying much emphasis on the solar energy so after some years we may expect that every household and also every electrical system is powered by solar or the renewable energy source.
