Realization of Thin MC-Silicon Pert-Type Bifacial Solar Cells in Industrial Environments

We present bifacial solar cells processed with a sequence suitable for industrial production. This method uses the LPCVD silicon nitride deposition based on DCS (dichlorosilane) or BTBAS (bis-(tertiary butyl amino)-silane). The bifacial solar cell process on wafers of 200 mum thickness has the following steps: (1) boron doped BSF of R_sheet =60 ohm/sq; (2) POCl₃ emitter (on front side) of R_sheet= 50-55 ohm/sq; (3) thermal oxidation of the wafer surfaces; (4) the deposition of DCS or BTBAS based LPCVD silicon nitride on either sides of the wafer (5); finger grid printing on both sides and firing; (6) edge isolation. The solar cells produced with the DCS based silicon nitride process exhibit fill factor (FF) values of 76% on p-type and 75% on n-type solar cells with a rear to front efficiency ratio eta_rear/eta_front of 67% for the p-type solar cells and 43% for the n-type solar cells. The solar cells with the BTBAS silicon nitride show FF values close to 72% and eta_rear/eta_front 68% for p-type solar cells