2 Describe stepbystep how a PV cell converts solar radiation

2. Describe step-by-step how a PV cell converts solar radiation into electricity (Semi-conductor, Dopant, p-n junction, Electron-hole pair formation).

3. What is band gap energy? Why are PV cells inherently low in efficiency?

4. Explain ways to improve the efficiency of PV cells and the direction of research and development which can lead to higher efficiency PV cells.

Solution

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 significant number of free electrons in the crystal. This is the basic reason of producing electricity due to photovoltaic effect. Photovoltaic cell is the basic unit of the system where photovoltaic effect is utilized to produce electricity from light energy. Silicon is the most widely used semiconductor material for constructing 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 bond between them. In this way silicon crystal gets a tetrahedral lattice structure. While light ray strikes on any materials some portion of light is reflected, some portion is transmitted through the materials and rest is absorbed by the materials.

A band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors

Ways to increase solar efficiency:
Make an Informed Decision:
The most important thing you can do is to make an informed decision while purchasing a solar panel. By doing this, you can find out which system offers the best value for your money as well as ensure that you get the best output from your solar system. Check out newer models of solar cells that give you improved levels of energy conversion. These models incorporate at least two layers of materials that are not similar with dissimilar sensitivities of wavelength.
Use a Solar Concentrator:
Solar light can be concentrated with the help of a solar concentrator. The purpose of these concentrators is to concentrate the light falling on a large area to smaller areas. Large mirrors or other devices are used in the facilitation of the task. Thus, the overall efficiency of solar cells, which are generally very expensive, can be increased. You not only get more energy but also save money.
Correctly Install Your Photovoltaic Panels
Photovoltaic panels should be installed correctly. The orientation as well as the angle it tilts at should be right. This would ensure that the panels receive optimal sunlight all through the day, as well as all through the year. The orientation of your solar panels should be more toward the true south if you live in the northern hemisphere. Similarly, they should be facing the north if you are in the southern hemisphere. The panels should be tilted in such a way that they receive sunshine directly without any obstruction from 9 am to 3 pm.
Avoid Shaded Areas:
Ensure that your solar cell is not shaded as this would have an adverse effect on the power output. This is especially true when you connect your solar cells in a series. If a photovoltaic cell is shaded, it causes the energy that is generated by its neighbors to be drained. This is because it acts as a resistor and helps in determining the total current.
Keep Your Solar Panels Clean:
If dust accumulates on the glass surface of your solar panel, it reduces the panel’s efficiency. As a result, the sunlight that would normally reach the photovoltaic cells gets dissipated. It is therefore important that you ensure that no dust and dirt collects on surface of your cell.
Prevent an Increase in Temperature:
The efficiency of your photovoltaic panel is affected by temperature levels. Efficiency drops as the temperature gets higher. Care should be taken that there is a sufficient gap between the solar panels and the roof, as this would allow easy movement of air and prevent the heat from affecting your photovoltaic panels.