Gary Zhou 
Tesla appears to be working on some improvements to its Solar Roof tiles that may allow the company to release new variants of the solar flagship product. In a recently published patent, these future solar roof enhancements were explored extensively which outlined how the electric car and energy company plans to roll out tiles with a better, more seamless look.
Solarglass Roof Tiles from Tesla are now one of the most aesthetically appealing PV systems on the market. The construction of a solar roof requires the installation of both PV and non-PV roof tiles, and this could cause some problems, according to Tesla. There would be several angles or occasions when it is possible to discern which tiles have solar cells and which do not, since some tiles do not have solar cells in them.
Tesla described this issue in the sense of its patent, entitled “System and Method for Improving Color Appearance of Solar Roofs” and published on February 11, 2021.
“When viewed from a shallow angle (e.g., when the roof is viewed from the street), the dark-colored photovoltaic structures can become visible. The color contrast between the photovoltaic structures and the glass cover can create a scene that is not aesthetically pleasing… Although the non-PV roof tiles can include similar glass covers as those of the PV roof tiles, the absence of embedded photovoltaic structures can result in the non-PV roof tiles having a different color appearance than that of the PV roof tiles.”
Tesla states that these problems are due to many factors, including slight imperfections during the development process of the Solar Roofs, or the fact that when viewed under different lighting and at different viewing angles, PV roof tiles appear to look different. There are ways to get around these problems, according to Tesla, such as implementing a rigorous color management system and some improvements in the production line of Solar Roof tiles.
“First, to reduce the color contrast within a PV roof tile, the PV roof tile can encapsulate polycrystalline-Si-based photovoltaic structures. By controlling the size and pattern of the surface texture of the polycrystalline-Si-based photovoltaic structures, one can reduce the “glow” of the photovoltaic structures. While keeping the front cover of the roof tile transparent, the back surface of the back cover can be coated with a layer of paint that matches the color of the textured surface of the photovoltaic structures to reduce the color contrast within the PV roof tile. A similar paint layer can also be deposited onto the back surface of the non-PV roof tiles.”
“As a result, the color appearance of the PV and non-PV roof tiles can be quite similar. Moreover, when assembling the PV roof tiles, the embedded photovoltaic structures are fed into the production line following a predetermined color pattern such that a majority of PV roof tiles contains solar cells of a similar color and PV roof tiles of different colors are evenly or randomly mixed to prevent clustering of colors on a roof.”
Through these techniques, Tesla noted that solar roof tiles that have much less glow than traditional integrated PV systems can be made. The patent also discussed how it was possible to use reactive ion etching (RIE) techniques to produce textured PV roof tiles. These refer to photos of the different variants of the Solar Roof that Elon Musk revealed in 2016, which included textured tiles that represented the appearance of materials such as slate and clay.
“The surface of a polycrystalline-Si-based solar cell can be textured using a reactive ion etching (RIE) technique. In further embodiments, the feature size of the RIE-textured surface can be less than 1 micron (i.e., 0.5 micron or less). In alternative embodiments, the surface of the solar cells can have pyramid texturing with the base width of the pyramids being less than 1 micron (e.g., 0.7 micron or less). Compared to the textured surface of a monocrystalline-Si-based solar cell, the RIE-textured surface of the polycrystalline-Si solar cells can have improved surface uniformity. As a result, the PV roof tiles can have reduced color flop and glow.”
“In alternative embodiments, reducing the cell glow can be achieved through specifically designed anti-reflection coating. This specially designed anti-reflective coating (AR) on a monocrystalline-Si-based solar cell surface can include materials with a higher refractive index than a conventional AR coating (e.g., an indium tin oxide (ITO) coating). More precisely, the specifically designed AR coating can include a layer of SiNx or a SiOxNy /SiNy double layer structure. As a result, the cell glow can be reduced by three- to eightfold with low (e.g., less than 5%) power loss.”
Elon Musk has stated that the Solar Roof will be an integral part of Tesla’s growth in 2021, with the CEO saying that this year its potential will be apparent. In view of the ongoing implementation of the integrated PV system by the company and the production of better Solar Roof designs, it will only be a matter of time before more Tesla’s flagship residential solar product customers have more design options available.
Read Tesla’s recently-published Solar Roof patent could be accessed here.
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