TY - GEN
T1 - Passivation and carrier selectivity of TiO2 contacts combined with different passivation layers and electrodes for silicon solar cells
AU - Boccard, Mathieu
AU - Yang, Xinbo
AU - Weber, Klaus
AU - Holman, Zachary C.
N1 - Publisher Copyright:
© 2016 IEEE.
PY - 2016/11/18
Y1 - 2016/11/18
N2 - Titanium dioxide (TiO2) films have previously been demonstrated to function as electron-selective contacts to silicon solar cells, and an efficiency of 21.6% has been reported for a cell featuring a full-area TiO2 contact. However, the passivation quality of TiO2 contacts still falls short of that possible with best-in-class contacts based on, e.g., hydrogenated amorphous silicon (a-Si:H). We investigate here the performance of a-Si:H/TiO2 stacks as electron-selective, passivating contacts. We show that combining a-Si:H with TiO2 can result in excellent surface passivation (lifetime close to 3 ms for textured CZ wafers), especially for 7.5-nm-thick TiO2 capping layers. However, initial cell results show that such a-Si:H/TiO2 stacks give poorer efficiencies than TiO2 only, with extremely low fill factors due to S-shaped current-voltage curves. Also, the role of the rear electrode becomes apparent when substituting Al for an ITO/Ag stack: the latter has significantly lower open-circuit voltage and fill factor than the former. Combining a TiO2/Al rear electron contact (with no a-Si:H) and an intrinsic a-Si:H/p-type a-Si:H front hole contact, we demonstrate a double heterojunction silicon solar cell with an efficiency of approximately 15%. Furthermore, a full metal-oxide heterojunction cell that combines a molybdenum oxide (MoOx)/ITO hole contact with the TiO2/Al electron contact achieves an efficiency of 11%.
AB - Titanium dioxide (TiO2) films have previously been demonstrated to function as electron-selective contacts to silicon solar cells, and an efficiency of 21.6% has been reported for a cell featuring a full-area TiO2 contact. However, the passivation quality of TiO2 contacts still falls short of that possible with best-in-class contacts based on, e.g., hydrogenated amorphous silicon (a-Si:H). We investigate here the performance of a-Si:H/TiO2 stacks as electron-selective, passivating contacts. We show that combining a-Si:H with TiO2 can result in excellent surface passivation (lifetime close to 3 ms for textured CZ wafers), especially for 7.5-nm-thick TiO2 capping layers. However, initial cell results show that such a-Si:H/TiO2 stacks give poorer efficiencies than TiO2 only, with extremely low fill factors due to S-shaped current-voltage curves. Also, the role of the rear electrode becomes apparent when substituting Al for an ITO/Ag stack: the latter has significantly lower open-circuit voltage and fill factor than the former. Combining a TiO2/Al rear electron contact (with no a-Si:H) and an intrinsic a-Si:H/p-type a-Si:H front hole contact, we demonstrate a double heterojunction silicon solar cell with an efficiency of approximately 15%. Furthermore, a full metal-oxide heterojunction cell that combines a molybdenum oxide (MoOx)/ITO hole contact with the TiO2/Al electron contact achieves an efficiency of 11%.
KW - TiO2
KW - carrier-selective contact
KW - crystalline silicon solar cell
KW - electrode
KW - passivation
UR - http://www.scopus.com/inward/record.url?scp=85003443923&partnerID=8YFLogxK
U2 - 10.1109/PVSC.2016.7750072
DO - 10.1109/PVSC.2016.7750072
M3 - Conference contribution
AN - SCOPUS:85003443923
T3 - Conference Record of the IEEE Photovoltaic Specialists Conference
SP - 2403
EP - 2407
BT - 2016 IEEE 43rd Photovoltaic Specialists Conference, PVSC 2016
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 43rd IEEE Photovoltaic Specialists Conference, PVSC 2016
Y2 - 5 June 2016 through 10 June 2016
ER -