9.2 Types of solar cells and materials

Solar cells come in various types, each with unique properties. Crystalline silicon cells dominate the market, offering high efficiency and stability. Thin-film cells, though less efficient, provide flexibility and potential cost savings. These differences stem from their materials and manufacturing processes.

Advanced solar cell materials push the boundaries of efficiency and versatility. Gallium arsenide excels in space applications, while perovskites show rapid improvement. Organic photovoltaics offer printable solutions, and multi-junction cells maximize light absorption. These innovations drive the future of solar energy.

Crystalline and Thin-Film Solar Cells

Crystalline Silicon Cells

Top images from around the web for Crystalline Silicon Cells

• 

  Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission ... View original

  Is this image relevant?

• 

  High-efficiency crystalline silicon solar cells: status and perspectives - Energy ... View original

  Is this image relevant?

• 

  Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission ... View original

  Is this image relevant?

• 

  High-efficiency crystalline silicon solar cells: status and perspectives - Energy ... View original

  Is this image relevant?

1 of 2

Top images from around the web for Crystalline Silicon Cells

• 

  Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission ... View original

  Is this image relevant?

• 

  High-efficiency crystalline silicon solar cells: status and perspectives - Energy ... View original

  Is this image relevant?

• 

  Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission ... View original

  Is this image relevant?

• 

  High-efficiency crystalline silicon solar cells: status and perspectives - Energy ... View original

  Is this image relevant?

1 of 2

• Widely used in solar panels due to their high efficiency and stability
• Made from high-purity, single-crystal silicon wafers or polycrystalline silicon
• Single-crystal silicon cells have higher efficiencies (up to 26%) but are more expensive to manufacture compared to polycrystalline cells (efficiencies around 22%)
• Fabrication process involves cutting silicon wafers, doping them with impurities (boron and phosphorus) to create p-n junctions, and adding electrical contacts
• Require a relatively thick layer of silicon (around 200 μm) to absorb sufficient sunlight, making them more rigid and heavier compared to thin-film cells

Thin-Film Solar Cells

• Consist of thin layers of photovoltaic materials deposited on a substrate (glass, plastic, or metal)
• Thinner layers (1-10 μm) allow for more flexible and lightweight solar panels compared to crystalline silicon cells
• Lower efficiencies than crystalline silicon cells but have the potential for lower manufacturing costs and better performance in low-light conditions
• Three main types of thin-film solar cells:
  1. Amorphous silicon (a-Si): Non-crystalline form of silicon with efficiencies around 6-8%, often used in small-scale applications (calculators, portable electronics)
  2. Cadmium telluride (CdTe): Efficiency around 18-22%, less expensive than crystalline silicon but contains toxic cadmium, raising environmental concerns
  3. Copper indium gallium selenide (CIGS): Efficiencies up to 23%, composed of non-toxic materials, but more complex and expensive to manufacture compared to CdTe

Advanced Solar Cell Materials

Gallium Arsenide (GaAs) Solar Cells

• High-efficiency solar cells with record efficiencies above 29% for single-junction cells
• Direct bandgap semiconductor with excellent light absorption properties, requiring a thinner layer (a few microns) compared to silicon
• Suitable for high-temperature and high-radiation environments, making them ideal for space applications
• More expensive to manufacture than silicon cells due to the rarity of gallium and the complex fabrication process

Perovskite Solar Cells

• Emerging solar cell technology with rapidly increasing efficiencies (from 3.8% in 2009 to over 25% in 2020)
• Perovskite materials have a crystal structure of the form ABX3 (e.g., methylammonium lead iodide, CH3NH3PbI3)
• Can be processed using low-cost, solution-based methods (spin-coating, inkjet printing) at lower temperatures compared to silicon cells
• Challenges include improving long-term stability and addressing concerns about the toxicity of lead-based perovskites

Organic Photovoltaics (OPV)

• Solar cells based on organic semiconductors (polymers or small molecules) that can be processed from solution
• Potential for low-cost, high-throughput manufacturing using printing techniques on flexible substrates
• Lower efficiencies (around 15-18%) compared to inorganic solar cells, but can be improved through tandem cell architectures and optimizing device structures
• Advantages include semi-transparency, light weight, and the ability to tune properties through molecular design

Multi-Junction Solar Cells

• Combine multiple p-n junctions with different bandgap materials to absorb a wider range of the solar spectrum
• Each junction is optimized to absorb a specific wavelength range, reducing thermalization losses and increasing overall efficiency
• Record efficiencies above 47% have been achieved using multi-junction cells based on III-V semiconductors (GaAs, InGaP, InGaAs)
• Typically more expensive than single-junction cells due to the complex fabrication process and the use of rare materials
• Primarily used in concentrator photovoltaic systems, where sunlight is focused onto a small area of the cell using lenses or mirrors to increase efficiency and reduce material costs