Closing the gap between n- and p-type silicon heterojunction solar cells: 24.47% efficiency on lightly doped Ga wafers

Silicon heterojunction (SHJ) solar cells can be formed using n-type or p-type silicon wafers. To foster the increasing industrial interest of SHJ, cheaper p-type wafers with a good availability might be preferred, but until today, they yield lower cell efficiency compared with n-type and show instabilities in the particular case of boron doping. This work shows that the production flow of high performance rear-junction bifacial n-type cells can be applied to front-junction p-type cells without process alterations and with a loss of efficiency as low as -0.3%(abs) provided that the wafer bulk lifetime is high enough. For this, we propose the use of wafers with gallium doping on which we obtained on a semi-industrial pilot line SHJ p-type cells mostly stable under moderated heat and light and with an efficiency closed to n-type references. The best p-type cell was externally certified at 24.47% total area.

Automated summary

This study demonstrates that by using gallium-doped wafers, it is possible to achieve efficiency in front-junction p-type cells comparable to rear-junction bifacial n-type cells without process alterations.