Novel Interconnection Process for Lightweight Flexible Photovoltaic Modules

Individual solar cells are low-voltage high-current devices that must be connected in series to raise the module voltage for efficient use and transmission. Monolithic series interconnection, by laser scribing at the submodule level, is the preferred approach, because this type of interconnection is faster and less costly compared to external interconnection with grids and bus bars. However, in the case of solar cells fabricated on flexible susbtrates like polyimides, traditional laser scribing does not work well. Consequently, manufacturers use other interconnection techniques, such as grid application and screen printing, which are performed at various steps along the solar cell fabrication sequence. Manufacturing costs could be reduced if all interconnection steps could be performed at one point during the manufacturing process, using a simplified efficient technique that avoids the disadvantages of screen printing or grid application. This project will develop a process and required equipment for the post-deposition series interconnection of flexible solar cells. By combining scribing and ink-jet deposition technologies, all steps required for interconnection will be performed at one point near the end of the manufacturing process. Phase I will verify that interconnects perform satisfactorily and that the concept can be implemented on a large scale. The performance of each critical step (scribing, chemical application by ink-jet, etching) of the interconnection process will be tested on solar cells with available equipment. Commercial Applications and other Benefits as described by the awardee: Lightweight, flexible, monolithically-integrated solar cells should find use as portable battery chargers for communication devices and other portable electronic devices. A 5W photovoltaic battery charger, which weighs less than 50 grams and could be rolled up to the size of a small pen, could cost less than $30 and have a large consumer market. Flexible photovoltaics also should find use in space applications, where the high power-to-weight and power-to-stowed-volume ratios of these cells would be an important advantage.