Codiffused bifacial n-type solar cells (CoBiN)

We present codiffused bifacial n-type (CoBiN) solar cells on 156 mm Czochralski grown (Cz) Si wafers with peak efficiencies of 19.6 % fabricated using a lean industrial process. Simultaneous diffusion of phosphorus back surface field (BSF) and boron emitter in one single tube furnace process, the so called codiffusion, leads to a significant process simplification. Manipulation of the borosilicate glass (BSG) layer, deposited by atmospheric pressure chemical vapor deposition (APCVD) prior to the POCl3 based codiffusion process, allows for emitter profile tuning, without influencing the phosphorus doped BSF. Analytical simulations concerning the BSF identify the dark saturation current density of the passivated part of the BSF J(0pass), BSF as the parameter that allows for maximum improvement of cell efficiency.