What is a vacuum solar panel, and where can it be used?
Why should I choose a vacuum-based manufacturing process? What advantages does that technique offer over other available PV manufacturing methods, such as printing and evaporation?
Answer: Today’s methods for PV manufacturing include sputtering (PVD), PECVD, printing, evaporation, and more. However, vacuum-based processes such as PVD and PECVD offer definite benefits that the other methods simply can’t deliver. Specifically, PVD and PECVD provide atomic-level control that enables you to more precisely determine film characteristics, such as stoichiometry, crystallinity, and uniformity across the substrate. PVD and PECVD also produce fewer defects than other methods. This high level of control culminates in two critical benefits for today’s solar panel manufacturers: greater PV efficiency and increased throughput.
Figure: Simplified representation of a sputtering (PVD) process—Other PV manufacturing methods can’t match the precision of vacuum-based processes, which work on the atomic level.
The figure above illustrates the atomic-level behavior of a sputtering process. In the first step of this process (left), argon atoms are ionized. An accelerated electron strikes an atom in an inelastic collision that removes an electron from the atom, creating an Ar+ ion. Next, during the sputtering step (middle), the Ar+ ion is accelerated toward the negative cathode surface. It strikes with enough energy to remove target material. In the final phase (right), the target material reaches the substrate surface, where it is deposited as a thin film.
Another benefit of using a vacuum-based process is the fact that within the areas of PVD and PECVD, a great deal of expertise and technological development has been amassed that can be applied directly to PV manufacturing. AE offers over three decades of experience, as well as a comprehensive and highly developed product portfolio that enables an exceptional level of control over film properties compared to other subsystem manufacturers. For example, our products enable a lower defect rate, which not only increases solar cell efficiency, but allows higher-power operation as well, resulting in increased throughput. Higher-power operation also enables successful coating of large-area substrates. Our Crystal® AC power supply has a long track record of success in achieving the power levels required for architectural glass applications (including low-E coatings for the passive solar market), which also makes it ideal for the increasing substrate sizes in the PV industry. Please see our Design Aspects of Large-Area Coating Supplies white paper for more information.
In fact, AE’s expertise in large-area coating for industries such as FPD and architectural glass has direct application to large-area PV manufacturing. We’ve honed our products, technologies, and expertise in these adjacent markets, as well as the semiconductor industry, which, of course, is the original silicon-wafer application. You could say that AE cut its teeth in the semiconductor industry, an industry that requires extreme manufacturing precision and allows little or no margin for error. In fact, semi has the smallest process window of any industry. Therefore, our products and technologies are designed around the concept of precision, a fact that benefits solar in the form of increased cell efficiency and process throughput.