Solar glass, as a core material for photovoltaic modules and building-integrated photovoltaic (BIPV) systems, has a significant impact on its performance, photovoltaic conversion efficiency, weather resistance, and service life. Its primary material is typically composed of a base glass layer and a functional coating or interlayer. The combination of these materials aims to balance key performance indicators such as light transmittance, infrared reflectivity, impact resistance, and durability. The following describes the base glass material and functional modified materials.
1. Base Glass Materials
The base layer of solar glass is typically made of high-transmittance float glass, primarily composed of silicates, including silicon dioxide (SiO₂, approximately 70%-72%), sodium oxide (Na₂O, 12%-15%), calcium oxide (CaO, 8%-10%), and small amounts of magnesium oxide (MgO) and aluminum oxide (Al₂O₃). High-purity quartz sand (SiO₂ content ≥99%) is the core raw material that determines light transmittance. High-temperature melting creates a uniform amorphous structure, minimizing light scattering and generally achieving visible light transmittance exceeding 90% (compared to approximately 85%-88% for conventional architectural glass).
To further enhance optical performance, some high-end products utilize ultra-clear float glass (iron content ≤0.015%). Its low iron content significantly reduces green spectrum absorption, resulting in a nearly colorless and transparent glass. This makes it particularly suitable for photovoltaic curtain walls and skylights, where color reproduction is crucial. Furthermore, controlling the annealing curve during the melting process optimizes the internal stress distribution of the glass, improving its resistance to wind pressure and thermal shock (for example, tempering treatment in accordance with GB/T 15763.1-2009 standard, with a surface compressive stress ≥90 MPa).
II. Functional Modified Materials
To enhance the power generation efficiency and environmental adaptability of solar glass, specific functional layers must be integrated into its surface or structure. These layers are primarily categorized into the following three categories:
1. Anti-reflective Coating (ARC)
ARCs are typically composed of a silicon dioxide (SiO₂)-titanium dioxide (TiO₂) composite nanofilm. By controlling the film thickness (approximately 100-150 nm, approximately half the wavelength of visible light), they create a destructive interference effect, reducing the reflectivity of the glass surface from 8%-10% for ordinary float glass to 1%-3%, thereby increasing overall light transmittance. Some products utilize a sol-gel method to create a multilayer, graded-refractive-index coating system, further broadening the effective spectral range (covering the 380-1100 nm range).
2. Infrared Reflective Layer (Low-E or Photovoltaic Selective Film)
To address the temperature sensitivity of photovoltaic modules (crystalline silicon cell efficiency decreases by approximately 0.4% for every 1°C increase in temperature), some solar glass incorporates metal oxide or silver-based composite films (such as indium tin oxide (ITO), silicon nitride (Si₃N₄), or silver-nickel-chromium alloy laminates). These selectively reflect thermal radiation in the near-infrared band (700-2500nm), reducing heat buildup within the module. For example, a single silver Low-E film can achieve an infrared reflectivity exceeding 70%, while a double silver film can further increase this to 85%, while maintaining high visible light transmittance (>85%).
3. Interlayer or Encapsulant
In photovoltaic module applications, solar glass is often laminated with an interlayer of polyvinyl butyral (PVB) or ethylene vinyl acetate (EVA), forming a "glass-EVA/cell-EVA-backsheet" structure. PVB offers excellent impact resistance and UV-blocking properties (transmittance <1%), making it suitable for architectural safety glazing. EVA, however, has become a mainstream encapsulation material due to its stronger adhesion to silicon cells (forming a three-dimensional network structure after cross-linking and curing). Its transmittance exceeds 90% and it can withstand long-term thermal cycling from -40°C to 120°C.
III. Material Innovation for Special Scenarios
With technological advancements, some new solar glass technologies are exploring perovskite quantum dot-doped glass (using a sol-gel method to uniformly disperse photosensitive materials within a glass matrix for broad-spectrum absorption) or flexible polymer-based glass (such as PET-glass composites, suitable for curved photovoltaic buildings). Furthermore, self-cleaning glass, coated with a titanium dioxide (TiO₂) photocatalytic film, decomposes organic matter and dirt under UV light. Combined with a hydrophobic coating (contact angle >100°), it reduces dust adhesion, further reducing maintenance costs.
In summary, solar glass material design is a comprehensive fusion of materials science, optical engineering, and energy technology. Its core lies in maximizing photovoltaic conversion efficiency while ensuring structural safety through the high light transmittance of the base glass and the precise control of the functional layers. As demand for photovoltaic building integration grows in the future, composite materials that combine aesthetic design with high performance will become a research and development priority.
