As a critical part of the photovoltaic manufacturing process, metallization is applicable to both crystalline silicon and thin-film technologies. As such, it’s not only important that manufacturers get it right, but also, that they do so while driving down cost-per-watt and increasing cell efficiency. Then and only then will we arrive at that coveted milestone of grid parity.
The ongoing commercialisation of the photovoltaic marketplace has been facilitated in part by the emergence of companies pioneering process-led efficiencies to enhance our ability to deliver on these all-important drivers. One such company is DEK Solar, a screen printing specialist pre-eminent in the field for its high accuracy commercial mass imaging process expertise and equipment solutions. Today, DEK Solar is helping the industry harness the power of screen printing to deliver improvements in throughput, accuracy and yield.
The screen printing advantage
There are currently two manufacturing technologies for PV cells. Those fabricated on bulk silicon substrates currently account for more than 90% of global production. These are built up using thick-film production techniques, by depositing an array of fine current-collector fingers on the topside of the substrate, creating a series of wider bus bars for electrical interconnection purposes on the topside and backside, and then applying an aluminium metallization layer to the bottom side. In this way, the PV cell is built up through a sequence of processes, each of which is relatively easy to implement and control using the latest equipment now emerging to service the growing number of PV cell producers.
Thin-film PV technology is a newer alternative, which not only allows cell arrays to be fabricated on silicon but also enables substrates such as flexible polymer, steel or glass sheets to be used. This will allow energy harvesting capabilities to be embedded directly in windows and other panels for office buildings, warehouses and many other locations.
In both cases, screen printing is the optimum process to deliver metallization; it is the process of choice for all progressive solar cell producers. Essentially evolved from the ancient art of silk screen fabric printing – examples of which date back to 10th Century China – screen printing has become a precision science deployed in a wide range of innovative industrial applications from product labels to embedded passive electronic components and conductive inks.