Development, characterization and interface engineering of films for enhanced amorphous silicon solar cell performance

We are reporting comprehensive efforts for development and characterization of thin film PECVD a:SiH and TCO materials, and novel surface modification techniques to enhance solar cell performance. All process development and cell fabrication was conducted on 200 mm substrate wafers on CMOS manufacturing platform tools. Entire process parameter space of our PECVD tool was explored to enable increased understanding for process parameter effects on phase transition between amorphous and micro-crystalline Si films as well as film quality. In-depth characterizations helped understood material properties. It was observed that a range of crystallinity can be achieved by carefully tuning the plasma conditions. A PVD process for in-situ highly textured TCO surface with high overall transmittance was developed. Novel modification techniques were designed, which significantly improved open circuit voltage (V_oc) and current density (J_sc). Highest V_oc and J_sc achieved till date is 920 mV and 15mA/cm² on 0.16cm² devices. Initial efficiency of 8.4% is also reported on a 0.16cm² single junction device.