Material properties of LPCVD processed n-type polysilicon passivating contacts and its application in PERPoly industrial bifacial solar cells

We present a detailed material study of n+-type polysilicon (polySi) and its application as a carrier selective rear contact in a bifacial n-type solar cell comprising fire-through screen-printed metallization and 6" Cz wafers. The cells were manufactured with low-cost industrial process steps yielding Vocs from 676 to 683 mV and Jscs above 39.4 mA/cm2 indicating an efficiency potential of 22%. The aim of this study is to understand which material properties determine the performance of POCl3-diffused (n-type) polySi-based passivating contacts and to find routes to improve its use for industrial PERPoly (Passivated Emitter Rear PolySi) cells from the point of view of throughput, performance, and bifacial application. This paper reports on correlations between the parameters used for low pressure chemical vapour deposition (LPCVD), annealing, and doping on optical, structural, and electronic properties of the polySi-based passivating contact and the subsequent influence on the solar cell parameters.