A novel non-photolithographic patterning method for fabricating solar cells

In this work we propose and demonstrate a novel method to fabricate semiconductor devices using a shadow mask that allows selective deposition of PECVD layers and selective exposure of doped silicon regions. The exposed regions then act as seed layers for selective metallization by a process such as electroplating. A device structure taking advantage of this process can be completely done without any photolithographic steps. In semiconductor processes where submicron-feature sizes are generally not required and reducing cost of manufacturing is key (e.g. in solar cells), this proposed process flow could be really useful. We have fabricated a conventional diffused p-n junction monofacial solar cell on a monocrystalline silicon (c-Si) substrate using this method. Nickel is electrochemically grown to form front surface electrode. The monofacial solar cell fabricated with an un-optimized process shows an efficiency of 14.5% under AM1.5G one sun illumination. The feature size of metal electrodes formed in this way is 80μm and could be narrowed down to smaller size-width. Optimization of doping, surface passivation and metallization would improve the efficiency even further to values in the high teens by improving open circuit voltage (V_OC), current density (J_SC) and Fill Factor (FF).