Porous silica-based anti-reflective coating increases PV glass optical transmission by 5.2%

<p class="p1"><span class="s1">Researchers in Spain developed a porous silica anti-reflective coating for solar panels that boosts optical transmission while balancing durability and mechanical stability through optimized sol–gel chemistry.</span></p><p>A research team led by Spain's Center for Energy, Environmental and Technological Research (CIEMAT), has developed a novel anti-reflective (AR) coating for use in solar panels.</p>
<p>&#8220;By jointly tuning pore-forming agent concentration, thermal treatment, and silica precursor chemistry, we show that it is possible to tailor coatings that combine near-unity transmittance with mechanical and environmental stability suitable for real solar installations,&#8221; said corresponding author Gema San Vicente to <strong>pv magazine</strong>. &#8220;This balance is essential for solar systems, where even small optical gains are only meaningful if the coating survives years of outdoor exposure.&#8221;</p>
<p>&#8220;A particularly surprising finding was that prolonged thermal treatment does not necessarily improve durability,&#8221; she went on to say. &#8220;In highly porous coatings, longer calcination times significantly reduced mechanical resistance, despite maintaining excellent optical performance. This shows that processing conditions that seem beneficial from a materials perspective can have unintended negative effects when porosity is pushed to extreme levels.&#8221;</p>
<p>To balance optical performance and mechanical and environmental durability, the scientists tested different pore-forming agent concentrations, thermal treatment conditions, and silicon precursor ratios.</p>
<p>They prepared silica precursor solutions with varying ratios of methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS), specifically TEOS:MTES ratios of 50:50, 70:30, and 90:10. Ethanol and deionized water were then added in the presence of sulfuric acid as a catalyst to form the sol–gel solution. The mixture was stirred for 24 hours to promote hydrolysis and condensation reactions. Next, pore-forming agent Pluronic P-123 was added in concentrations between 0 and 3.3% v/v.</p>
<figure class="wp-caption aligncenter" id="attachment_338859" style="width: 600px;"><img alt="" class="size-medium wp-image-338859" height="450" src="https://www.pv-magazine.com/wp-content/uploads/2026/04/PV-3-600x450.png" tabindex="0" width="600" /><figcaption class="wp-caption-text">Solar transmittance gain vs bare glass <p><i>Image: CIEMAT-PSA </i></p>
</figcaption></figure>
<p>The coatings were deposited on 3-mm-thickness borosilicate glass substrates and polished silicon wafers. When different TEOS:MTES ratios were tested, the Pluronic concentration was kept at 2.5% v/v. In contrast, when the different Pluronic concentrations were analyzed, the TEOS: MTES ratio was kept at 50:50. All samples underwent thermal treatment at 500 C for 15 minutes or 1 hour to evaluate the effect of thermal treatment on the final coating properties.</p>
<p>According to the research team, the addition of Pluronic effectively reduced the refractive index, thereby enhancing AR properties by increasing porosity. At the same time, the TEOS:MTES ratio played a key role in determining the coatings' porosity and durability. Samples sintered at 500 C for 15 minutes maintained better abrasion resistance and structural integrity than those sintered for 1 hour.</p>
<p>Ultimately, optimal balanced performance was achieved with 2% v/v Pluronic and a TEOS:MTES ratio of 70:30. Moreover, <span class="list-content">an increase of up to 5.2% in optical transmission was achieved compared to bare glass</span>, with transmittance reaching 99.8% at 600 nm.</p>
<p>&#8220;We have a follow-up research focused on further improving the balance between optical performance and durability under real operating conditions,&#8221; Gema San Vicente concluded. &#8220;In particular, we are investigating double configurations, combining an external surface more durable and with anti-soiling properties to reduce sensitivity to moisture and soiling, with an internal ultra-high optical transparent layer.&#8221;</p>
<p>The new AR coating was presented in &#8220;<a href="https://www.sciencedirect.com/science/article/pii/S0264127526005253" rel="noopener" target="_blank">Tailored highly transparent porous silica coatings for enhanced optical and mechanical performance of solar covers</a>,&#8221; published in <em>Materials & Design. </em>Scientists from Spain's <a href="https://www.pv-magazine.com/2026/03/16/ciemat-unveils-large-area-multispectral-solar-simulator-for-pv-module-testing/" rel="noopener" target="_blank">CIEMAT</a>, the<a href="https://www.pv-magazine.com/2025/06/10/novel-photovoltaic-technique-to-charge-patterns-for-droplet-manipulation/" rel="noopener" target="_blank"> Autonomous University of Madrid</a>, and Slovenia's <a href="https://www.pv-magazine.com/2019/09/30/new-aluminum-batteries-for-renewables-storage/" rel="noopener" target="_blank">National Institute of Chemistry</a> have contributed to the research.</p>