Journal
IEEE JOURNAL OF PHOTOVOLTAICS
Volume 9, Issue 1, Pages 89-96Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JPHOTOV.2018.2878337
Keywords
Passivating contacts; POLO junction; polycrystalline silicon; thermal treatment; ZnO:Al
Funding
- Ministry for Science and Culture of Lower Saxony
- German Ministry for Economic Affairs and Energy [0325702]
- European Union's Horizon 2020 research and innovation program [727529]
- H2020 Societal Challenges Programme [727529] Funding Source: H2020 Societal Challenges Programme
Ask authors/readers for more resources
We investigate the enhancement in transparency and conductivity of aluminum doped zinc oxide (ZnO:Al) layers upon high-temperature annealing and its impact on contact resistance, as well as, on passivation properties of carrier selective junctions based on doped polycrystalline Si on a passivating silicon oxide (POLO). The temperature stability of these junctions allows annealing of the ZnO:Al/POLO combination up to 600 degrees C. We prepare ZnO:Al films by dc magnetron sputtering at room temperature. We determine the complex refractive index of ZnO:Al in dependence of post-deposition annealing (PDA) temperature by spectroscopic ellipsometry. High-temperature annealing improves the conductivity and reduces the absorption within ZnO:Al. The optical losses in a ZnO:Al/POLO stack are rather limited by the poly-Si layer than by the ZnO:Al. The sheet resistance improves from roughly 20 000 ohm/sq for 80 nm thick as-deposited ZnO:Al films to 72 ohm/sq after fast firing at 600 degrees C. At the same time, PDA cures the damage induced in the POLO junctions during ZnO:Al deposition. After PDA with AlxOy capping layers, the passivation quality even surpasses the initial level. A transmission electron microscopy analysis of the interface between the ZnO:Al and the underlying poly-Si reveals the formation of a silicon oxide like interfacial layer after PDA at 400 degrees C. This interfacial layer causes a high contact resistivity of the metal/ZnO:Al/POLO-junction and could limit the thermal budget for cell processing. Our results indicate that after successful process adjustment, ZnO:Al could substitute In-based transparent conductive oxides on POLO cells for cost reasons, as well as, enable a high efficiency potential.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available