Stoichiometry and Morphology Analysis of Thermally Deposited V₂O_5−x Thin Films for Si/V₂O_5−x Heterojunction Solar Cell Applications

In recent decades, dopant-free Si-based solar cells with a transition metal oxide layer have gained noticeable research interest as promising candidates for next-generation solar cells with both low manufacturing cost and high power conversion efficiency. Here, we report the effect of the substrate temperature for the deposition of vanadium oxide (V₂O_5−x, 0 ≤ X ≤ 5) thin films (TFs) for enhanced Si surface passivation. The effectiveness of SiO_x formation at the Si/V₂O_5−x interface for Si surface passivation was investigated by comparing the results of minority carrier lifetime measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. We successfully demonstrated that the deposition temperature of V₂O_5−x has a decisive effect on the surface passivation performance. The results confirmed that the aspect ratio of the V₂O_5−x islands that are initially deposited is a crucial factor to facilitate the transport of oxygen atoms originating from the V₂O_5−x being deposited to the Si surface. In addition, the stoichiometry of V₂O_5−x TFs can be notably altered by substrate temperature during deposition. As a result, experimentation with the fabricated Si/V₂O_5−x heterojunction solar cells confirmed that the power conversion efficiency is the highest at a V₂O_5−x deposition temperature of 75 °C.