PECVD BSG Diffusion Sources for Simplified High-Efficiency N-PERT BJ and BJBC Solar Cells

21.0%-efficient screen-printed n-PERT back-junction silicon solar cell with plasma-deposited boron diffusion source

“…The SiH 4 /B 2 H 6 gas flow ratio strongly influences R sheet,B and J 0,B of the resulting boron diffusion, as discussed in detail in [14]. The PECVD BSG layer thickness has no discernible impact on the resulting R sheet,B but affects J 0,B , as shown in [12]: For the highest gas flow ratio of 8% (red diamonds) we measure a minimum saturation current density of (4.9 70.5) fA/cm 2 and J 0,B values below 10 fA/cm 2 for all PECVD BSG thicknesses and for a minimum boron sheet resistance of (937 17) Ω/□.…”

“…For the boron drive-in from the BSG layer, we apply a two-stage co-diffusion process in a POCl 3 furnace as described in [14] and as shown in Fig. 2: In one high-temperature process, the B drive-in from the PECVD BSG is performed first in an N 2 ambient at 950°C for 60 min, and then a POCl 3 diffusion is applied at 829°C.…”

“…We perform lifetime measurements using a Sinton lifetime tester on symmetrically boron diffused test structures after AlO x /SiN y [14]. The B drive-in from the PECVD BSG layer is performed at 950°C in N 2 ambient.…”

Fast Co‐Diffusion Process for Bifacial n‐Type Solar Cells

“…Most co‐diffusion processes described in the literature first apply a high temperature plateau for boron‐diffusion from a single side pre‐deposited borosilicate glass (BSG) in nitrogen ambient. Thereafter, a lower temperature plateau is applied when POCl 3 is introduced to the furnace diffusion process for growth of the phosphosilicate glass (PSG) and phosphorus diffusion on the rear surface of the wafer . However, this comes along with prolonged process times of up to 250 min .…”

“…Thereafter, a lower temperature plateau is applied when POCl 3 is introduced to the furnace diffusion process for growth of the phosphosilicate glass (PSG) and phosphorus diffusion on the rear surface of the wafer . However, this comes along with prolonged process times of up to 250 min . This letter presents a strongly simplified co‐diffusion approach which is based on our CoBiN process .…”