Inkjet Masking for Industrial Solar Cell Processes

摘要

Masking by inkjet printing has potential benefits for solar cell manufacturing by improving the conversion efficiency and production yield. In industry and on lab scale it has been shown that there are many applications for inkjet masking to improve the solar cell efficiency. These applications include honeycomb texturisation, selective emitter, plating of front side electrodes and using inkjet masking for low-cost rear-side patterning for back-contact cells. Key success factors for inkjet masking are its small feature size and high flexibility. Furthermore the contact-less print method is in line with the general trend towards thinner wafers to reduce the material costs. However, inkjet technology is initially developed for graphical printing, which has less demanding print reliability criteria. In the photovoltaic (PV) industry one malfunctioning nozzle in the inkjet printing system can result in significant decreased device performance or clear visual defects. Therefore the transition from graphical printing to solar cell production cannot be made without a significant improvement in reliability. In 2011 OTB Solar B.V. started the development of the PiXDRO JETx, a high volume industrial inkjet printing system (up to 2400 wafers/hour) which addresses inkjet masking as a first application. For this application a joint development with Oce Technologies targets to demonstrate an inkjet print reliability and accuracy which meets the standards for solar cell manufacturing. The use of self-diagnosing print heads of Oce, redundant print strategies and the automation from OTB Solar form the basis to combine high reliability with industrial throughput and the printing of fine structures with a drop placement accuracy of 7.5μm 3sigma.