High temperature oxidation pre-treatment of textured c-Si wafers passivated by a-Si:H

High temperature oxidation pre-treatment of textured c-Si wafers passivated by a-Si:H

Limodio, G. (TU Delft Photovoltaic Materials and Devices)
D'Herouville, G. (Student TU Delft)
Mazzarella, L. (TU Delft Photovoltaic Materials and Devices)
Zhao, Y. (TU Delft Photovoltaic Materials and Devices)
Yang, G. (TU Delft Photovoltaic Materials and Devices)
Isabella, O. (TU Delft Photovoltaic Materials and Devices)
Zeman, M. (TU Delft Electrical Sustainable Energy)

Electrical Sustainable Energy

2019

This work shows an alternative surface cleaning method for c-Si wafers to replace the standard chemical procedures as RCA or HNO ₃ which involve hazardous chemicals or unstable processes. The method consists in a high-temperature oxidation treatment (HTO) performed in a classical tube furnace that incorporates organic and metal particles present on the c-Si surfaces in the growing SiO ₂ layer. The result is as a reliable pre-treatment method for obtaining less defective c-Si surfaces ready for solar cell fabrication after SiO ₂ removal. To test the surface passivation quality obtained with our alternative cleaning method, we grow amorphous silicon (a-Si:H) layers by plasma enhanced chemical vapor deposition on both sides of the c-Si wafer and systematically compare the effective carrier lifetime (τ _eff ) and implied V _OC (iV _oc ) to the wafer treated with the standard cleaning in our laboratory. We optimize HTO treatment time reaching τ _eff of ∼6 ms and iV _oc of 721 mV for the best sample. We ascribe the improved passivation quality using HTO to two concurrent factors. Firstly, the encapsulation of defects into SiO ₂ layer that is then etched prior a-Si:H deposition and secondly, to modification of the pyramids’ morphology that facilitates the surface passivation. SEM pictures and reflection measurements support the latter hypothesis.

Amorphous silicon passivation
Defect encapsulation
Silicon heterojunction solar cells
Thermal oxidation

http://resolver.tudelft.nl/uuid:30601b5d-2387-4c96-a512-d878b706bb48

https://doi.org/10.1016/j.mssp.2019.03.008

1369-8001

Materials Science in Semiconductor Processing, 97, 67-70

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2019 G. Limodio, G. D'Herouville, L. Mazzarella, Y. Zhao, G. Yang, O. Isabella, M. Zeman