With the increasing demand for clean and green energy globally, solar energy is gaining greater and greater popularity. Solar cells as the core component of solar energy systems are of the most importance. 

Here in this article, we will discuss the working principle, classification, advantages and disadvantages, and future development direction of solar cells so that you can have a comprehensive understanding of solar cells.

What is a solar cell

Solar cells, or photovoltaic (PV) cells, utilize semiconductor materials such as silicon. Simply stated, the photovoltaic effect is the excitation of electrons and current generated when photons (sunlight particles) hit semiconductor materials. The electrons move around the circuit, generating an electric current to be utilized by external devices.

The working principle of solar cells

1: The nature of converting light energy to electrical energy

The key principle of solar cells is the photovoltaic effect. Solar photons incident on semiconductor materials such as silicon, if the photon energy is greater than the bandgap width of the material, excite electrons from the valence band to flow into the conduction band to form electron hole pairs. Photo generated carriers are accountable to produce electrical energy.

2: PN junction separation effect

The key device of solar cells is the PN junction (a compound of P-type and N-type semiconductors). Within the PN junction, the carrier concentration difference establishes an internal electric field from the N region to the P region.

This electric field forces electrons to collect in the N region and holes to collect in the P region, generating a potential difference (voltage). When an outside circuit is made contact, electrons flow from the N region to the P region through the outside circuit, recombine with holes, generate a photocurrent, and achieve the conversion of light energy into electrical energy.

3: Materials and structure’s role

Semiconductor materials: silicon-based materials (monocrystalline silicon, polycrystalline silicon) have become mainstream since their bandgap width is about the same as the solar spectrum; Thin film materials (e.g., CdTe) are reduced in cost by being thinned.

Structural design: For example, PERC cells reduce recombination of carriers through the application of backside passivation, TOPCon cells maximize efficiency with the application of tunneling oxide layers, and HJT cells use amorphous silicon and crystalline silicon together to enhance interface performance.

4: Energy Conversion in Practical Applications

The efficiency of the solar cell depends on the rate of photon absorption (material), efficiency of carrier separation (PN junction mass), and control of energy loss (reduction of recombination and resistance).

In practical applications, through the adjustment of material purity, surface passivation technology, and multi-layer structures (perovskite stacked cells, for instance), the photoelectric conversion efficiency can be further enhanced, eventually reaching effective use of clean energy.

Summary

Generation of photo generated charge carriers → Internal electric field separation of charges → External circuit formation of current → Material and structure optimization to improve efficiency.