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
N1 - Funding Information:
We acknowledge Kate Fisher for wafer preparation and Laura Ding for MoOx deposition. The information, data, or work presented herein was funded in part by the U.S. Department of Energy, Energy Efficiency and Renewable Energy Program, under Award Number DE-EE0006335. Support was also provided by the Research Corporation for Science Advancement through Scialog Collaborative Innovation Award Number 23460.
Publisher Copyright:
© 2017 IEEE.
PY - 2017
Y1 - 2017
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 - Carrier-selective contact
KW - Crystalline silicon solar cell
KW - Electrode
KW - Passivation
KW - TiO
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U2 - 10.1109/PVSC.2017.8366554
DO - 10.1109/PVSC.2017.8366554
M3 - Conference contribution
AN - SCOPUS:85048458375
T3 - 2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017
SP - 1526
EP - 1530
BT - 2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 44th IEEE Photovoltaic Specialist Conference, PVSC 2017
Y2 - 25 June 2017 through 30 June 2017
ER -