How Different Materials Impact Solar Energy Efficiency?

Introduction

Solar energy is a type of renewable energy which uses sunlight to generate electricity, and has already gained significant attention from the energy industry due to its sustainability. In our world, solar panels now create approximately 5.4% of the global electricity.

Solar panels produce electricity from sunlight through the photovoltaic effect, a process that generates voltage and electric current by exposure to light, which is the key technology to clean energy. However, as solar panels require sunlight to generate electricity, its efficiency fluctuates from various factors: climate conditions, angle, and sunlight intensity. Its material of construction is one of the major factors to decide the efficiency of solar panels. 

The most commonly known type of solar panels are:

• Monocrystalline Silicon

• Perovskite Solar Cells

• Quantum Dot Solar Cells

• Multi Junction Solar Cells

Each type of solar panel utilizes different materials and technology with unique properties to maximise efficiency and reduce cost of the energy production.

Understanding the effects of these materials is essential for optimizing the efficiency and performance of the solar panels and even determining the weaknesses to improve the energy efficiency.

The Science Behind Solar Energy Conversion

Solar energy conversion involves transforming light into electricity through the photovoltaic effect, a process that occurs in the semiconductor inside the solar cells. 

1. When light (particles called photons) collide with the surface of solar cells, photons transfer their energy to negative charged electrons. 

2. This process causes the electrons to become excited, creating a positively charged hole in the semiconductor material. 

3. Due to their opposite charges, it creates an electric field forcing the free electrons to move towards the positively charged hole. 

4. Through this process, current is generated and collected by metal contact, also known as ‘finger’, attached to the solar cell. 

5. The external circuit attached to the semiconductor generates a direct current(DC) and is stored in a battery for later uses.

What is a P-N junction?

P-N junction is a combination of two semiconductors, p-type(positive) and n-type(negative). In the n-type material, there are extra electrons that can move freely due to its negative charge. In contrast, p-type materials have holes, which are the extra spaces where electrons could go. Although the holes are not particles, we treat them as positive charges because electrons can fit in. As two materials meet, electrons fill up the holes, creating a ‘junction’ where the charges balance out, and it forms an electric gate. This p-n junction allows current to flow in one direction, making it effective to conduct electricity in the  solar cells. 

Types of Solar Cells and Their Materials

There are several types of solar cells, each having different materials to achieve a high level of efficiency, durability and cost effectiveness. From the types of solar cells I have mentioned, the most common type is Monocrystalline Silicon, which uses pure silicon crystals. Monocrystalline Silicon is considered as ‘The Industry Standard’ due to its high efficiency and predominance in the photovoltaic(PV) market. Its silicon material is a highly efficient light absorbing material, pushing the efficiency up to 26.7% under lab conditions. Nevertheless, monocrystalline silicon requires more wafers (thin slice of semiconductor, used for the manufacturing of solar cells)  as it produces greater energy compared to other cells.

Another emerging technology is Perovskite Solar Cell, which uses perovskite structured material (such as methylammonium lead halide) as the active layer. Perovskite material is well known for its unique hybrid organic & inorganic structure and rapid advancing technology. Since 2009, the efficiency has significantly improved from 5% to 25.5% efficiency in 11 years of development. However, concerns on its stability and environmental impacts due to its lead based compounds, still needs to be addressed and verified before commercial uses.

Quantum Dot Solar Cell(QDSC) is a solar cell that uses quantum dots - tiny semiconductor particles - as a main light absorbing material. It is well known for its “tunable band gap” which can adjust depending on the wavelength and energy levels optimizing the absorption from the Sun. Despite its high production cost and complex process, QDSCs have potential to increase its efficiency up to 66%. 

Additionally, unlike monocrystalline silicon’s single p-n junction, Multi Junction Solar Cells are solar cells with multiple p-n junctions made of various semiconductor materials. This new technology can significantly enhance the efficiency of solar cells as it has different layers of semiconductor that absorbs different wavelengths of light, optimizing the efficiency up to 86.6% theoretically. However, their high cost makes them impractical for commercial use, limiting their uses to specialized roles, particularly in aerospace.

Conclusion

Ultimately, the efficiency of solar cells are influenced by types of material. While Monocrystalline silicon remains most widely used due to its high efficiency, emerging technologies such as perovskite, quantum dot, and multi junction solar cells offer a possibility of advancement and growth in the PV market. Each unique material comes with different strengths and drawbacks, whether its cost, sustainability, and complexity in production. As technology develops rapidly with the assistance of Artificial intelligence and continuous research, solar energy will be more efficient, affordable, and accessible to everyone.

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