Quality Criteria for Solar Cells – Current Status (2025-12) and Sample Values

Choosing the right solar cells is critical to the efficiency, longevity, and profitability of a solar system. The following describes the main quality criteria for solar cells that should be considered in the selection process, as well as the current example values for these criteria.

1. Efficiency (Efficiency)

Why important: Efficiency indicates how much solar energy the solar cell can convert into electrical energy. Higher efficiency means that more energy is generated on the same area.

Current status: The efficiency of modern monocrystalline solar cells is 18-22%. Thin film solar cells are often less efficient, with values of 10-13%.

Example values:

• Monocrystalline solar cells: 20-22% (e.g. solar modules from SunPower, LG)
• Polycrystalline solar cells: 15-18%
• Thin-film cells (CIGS): 10-13%

2. Performance class (power output)

Why important: The power of a solar module (in watts) is a measure of the energy generated under standard test conditions (STC). This value is crucial to determine the performance of an entire solar system.

Current status: High-quality monocrystalline solar modules have a performance of 300-400 watts per module. Thin film modules can also achieve higher values, but are usually larger due to their lower efficiency.

Example values:

• Monocrystalline modules: 330-380 watts (e.g. modules from Trina Solar, Canadian Solar)
• Polycrystalline modules: 270-330 watts
• Thin film modules: 150-200 watts

3. Temperature coefficient (Temperature Coefficient)

Why important: The temperature coefficient indicates how much the solar cell's power decreases as temperatures rise. Solar systems should be able to operate efficiently under different climatic conditions.

Current status: The temperature coefficient is typically -0.3% to -0.5% per °C. A lower value is better because the module then loses less power as the temperature rises.

Example values:

• Monocrystalline cells: -0.3% to -0.4% per °C
• Polycrystalline cells: -0.4% to -0.5% per °C
• Thin-film cells: -0.2% to -0.3% per °C

4. Durability and Warranty (Durability and Warranty)

Why important: Solar cells are a long-term investment. A long service life and a long warranty period provide assurance that the cells will continue to operate efficiently for decades.

Current status: Most manufacturers offer a Performance guarantee from 25 years, where the solar cells are still at least 80-90% should provide their rated power. The Product warranty is often at 10-12 years.

Example values:

• Performance guarantee: 80-90% after 25 years
• Product warranty: 10-12 years (e.g. for modules from SunPower, LG, Q CELLS)

5. Quality of materials (Material Quality)

Why important: The materials from which the solar cells are made influence their longevity, efficiency and resistance to environmental influences such as UV radiation, rain and dirt.

Current status: Monocrystalline modules with tempered glass, corrosion-resistant frames and high-quality semiconductor materials offer high quality and reliability.

Example values:

• Tempered glass: glass thickness of 3-4 mm
• Frame material: aluminum frame, often anodized for better corrosion protection

6. Low Light Performance (Low Light Performance)

Why important: In many areas the weather is often cloudy and there is little sunlight. Solar cells that operate efficiently in low light are particularly important in such conditions.

Current status: Modern monocrystalline cells offer good performance in low light and are therefore particularly advantageous in areas with frequent cloudy skies.

Example values:

• Monocrystalline modules: Good performance even at 200-300 W/m² (in low light)
• Polycrystalline modules: Tends to be slightly less efficient in low light than monocrystalline cells

7. Self-cleaning and maintenance needs (Self-Cleaning and Maintenance)

Why important: In areas with a lot of dust, dirt or pollen, dirt can build up on the solar cells and reduce efficiency. Some modern solar modules offer self-cleaning mechanisms, e.g. through special coatings.

Current status: Many manufacturers offer solar modules with Anti-dirt coatings or with Self-cleaning technology to minimize maintenance.

Example values:

• Hydrophobic coatings on glass that reduce the accumulation of dirt

8. Fire behavior (fire resistance)

Why important: The fire behavior of solar cells is a crucial safety factor. Solar cells that ignite quickly pose a major risk.

Current status: Solar panels are often used according to international standards such as IEC 61730 tested, which, among other things, regulate fire and safety regulations.

Example values:

• Fire class: Class C or better according to IEC 61730
• Fire protection class: Solar modules should be UL 1703 or IEC 61730 be certified, which includes a fire safety test

9. Costs (Cost)

Why important: The cost per watt is a major factor in the profitability of a solar system. Cheaper modules reduce initial investment, but lower costs may be accompanied by lower efficiency or shorter guarantees.

Current status: Prices for solar cells and modules have fallen sharply in recent years, making solar energy increasingly competitive.

Example values:

• Cost per watt (2023): Approximately 0.15-0.40 USD/watt depending on the module type and manufacturer

10. Certifications and standards

Why important: Certifications guarantee that the solar cells meet international standards and meet quality requirements.

Current status: Important certificates are IEC 61215 (Performance of solar modules), IEC 61730 (Safety standards) and UL 1703 (US standards).

Example values:

• Certifications: IEC 61215, IEC 61730, UL 1703

Summary

The main quality criteria for solar cells include the efficiency, the Performance class, the Temperature coefficients, the guarantee, the Material quality, the Low light performance, the Fire behavior and the Certifications. When purchasing solar modules, one should always pay attention to these factors in order to ensure a long-term profitable and reliable solar system.