Functional Glasses

Within the field of “Functional Glass,” Fraunhofer CSP investigates optically, mechanically, and chemically optimized glasses for use in photovoltaic modules. The focus is on anti-reflective, anti-soiling, and chemically strengthened surfaces, whose properties are systematically evaluated and further developed.

The glasses are iteratively optimized, processed into test and industrial modules, and analyzed with regard to energy yield and long-term behavior under various climatic conditions. The results provide a robust foundation for the development of high-performance, durable, and cost-effective functional glass solutions for PV applications.

Accelerated performance and durability analysis of functional layers

• Investigation of coated front glass samples in the form of test specimens or mini solar modules using solar simulators with variable spectra, angles of incidence, and illumination durations

Electrical characterization (IEC 60904-3)

• Measurement and analysis of I–V characteristics
• Determination of efficiency and additional electrical parameters
• Comparison of electrical performance depending on glass coatings

Optical performance evaluation (IEC 62805-2)

• Analysis of the impact on STC performance
• Evaluation of angular dependence of optical properties
• Use of spectroscopic methods to assess transmission and reflection of coated front glass

Thermal performance evaluation (IEC 61853-2)

• Analysis of cooling behavior
• Evaluation of temperature distributions and evolution under varying irradiation conditions
• Soiling and self-cleaning behavior (VDI 3956-1)
• Durability with regard to abrasion and cleaning (DIN SPEC 4867 → transitioning to DIN-ISO, IEC 62788-7-3)
• Lifetime stress testing (UV resistance, TCT, DH, HF) (IEC 61215)

Abrasion and cleaning mechanics testing for PV glass coatings

• Assessment of the damage potential of cleaning brushes under defined and variable cleaning parameters (brush type, suspension, test dust, speed, etc.) (DIN SPEC 4867, working mode 2)
• Evaluation of abrasion resistance under strictly defined cleaning loads using a rotating full-scale brush (DIN SPEC 4867, working mode 1)
• Linear brush abrasion tests for PV-coated glass (e.g., IEC 62788-7-3)

Challenge:
Newly developed sol-gel coatings for PV applications required cost-efficient performance evaluation.

R&D solution:

• Anti-reflective performance (STC and angle-dependent) demonstrated via power measurements on mini-modules with coated and reference glass
• Anti-soiling performance validated using a standardized laboratory test (soiling chamber), including initial soiling and post-cleaning behavior
• Abrasion resistance quantified using standardized cleaning test systems and compared to conventional AR-coated solar glass

Material compatibility and optical stability of PV glass with industrial cleaners

Challenge:
PV cleaning agents can chemically interact with module components, leading to degradation—particularly reduced optical transmission and associated performance losses.

R&D solution:

• Systematic testing of multiple commercial cleaners using standardized compatibility and corrosion tests
• Optical performance analysis before and after exposure identified significant differences between cleaning agents and quantified their impact on module performance

Comparative wear analysis of PV coatings under dry and wet cleaning

Challenge:
Brush cleaning can cause abrasion—unclear how dry cleaning compares to wet cleaning.

R&D solution:

• Quantification of coating degradation after 1,000 brush cycles using full-scale industrial brush systems
• Direct comparison between dry and wet cleaning conditions to assess damage potential

Challenge:
Colored PV modules must balance design flexibility with minimal efficiency losses and high durability.

R&D solution:

• Characterization of digital inks and optimization of lamination and adhesion processes
• Adjustment of print layouts and parameters to achieve target designs with minimal efficiency loss
• Development of high-quality, customized PV modules for architectural and representative applications