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The structural, optical, and electrical properties of thermal evaporation-deposited V2OX films for use in silicon heterojunction solar cells
N. Bandaru, R. Kanakala, R. Madaka, N. Dsouza, R. Maurya,
Published in Springer
Volume: 34
Issue: 12
Vanadium suboxide (V2Ox) has been suggested as a promising transition metal oxide for the development of selective contacts on high-performance crystalline silicon heterojunction solar cells. In this study, V2Ox thin films were deposited on wet-cleaned wafers (Cz n-type c-Si (111) with a thickness of 160 μm; cleaning steps include SAW damage removal, RCA1, RCA2, and HF dip) and Corning (Eagle 2000) glass substrates utilizing the thermal evaporation technique at a pressure of 5 × 10−5 mbar. V2Ox thin films were deposited with various thicknesses from 5 to 20 nm. Ellipsometry, XRD, AFM, UV–Vis analysis, minority carrier lifetime measurements using SINTON photoconductivity decay (PCD) and lifetime mapping by SEMILAB µ-PCD were used to figure out the structural, optical, and electrical properties of deposited V2Ox films. The thickness of these films was measured by the ellipsometry technique. The amorphous nature of the as-deposited films is confirmed by the XRD patterns, and their optical transmittance is in the range of 93 to 76% in the visible range for 5 to 20 nm for V2Ox films. At 1 sun illumination, the minority carrier lifetime values range from 220.40 ± 1.26 µs to 293.27 ± 0.63 µs. These values are within the range of well-passivated wafers, they translate into implied-VOC values ranging from 642 to 652 mV, indicating a high degree of surface passivation. Surface passivation could be caused by a sub-stoichiometric SiOx interlayer that forms when silicon bonds with oxygen. We postulate that the fixed charges acquired by the silicon sub-oxide layers create the field effect passivation. According to our experimental findings, a 10 nm-thick V2Ox film has the best optoelectronic properties, including a minority life-time of 293.27 ± 0.63 µs with an implied Voc of 652 mV. The findings are critical for the fabrication of hetero-junction silicon solar cells. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
About the journal
JournalJournal of Materials Science: Materials in Electronics