Structural, optical, and electrical properties of spray-pyrolyzed MoO₃ thin films by varying precursor molarity, as hole-selective contact for silicon-based heterojunction devices

Sub-stoichiometric molybdenum oxide (MoO₃) films are recurrently deposited on crystalline silicon (c-Si)-based devices by thermal evaporation. This technique necessitates high temperature, which offers limited control of oxide stoichiometry and therefore affects the control of hole-transport mechanism. In this work, the effect of precursor molarity on the properties of deposited MoO₃ films by spray pyrolysis at a substrate temperature of 300 °C was investigated. The molarity was varied in a range of 0.05 M to 0.2 M with 0.05 M increment. The films were characterized by analyzing their structural, morphological/composition, and electrical properties. X-ray diffraction findings revealed the growth of orthorhombic lamellar crystal structure with (0k0) preferred orientation. Field emission scanning electron microscopes images displayed nanobelts-like structure with improved grain size as the molarity increases. The typical diode parameters, such as ideality factor (n) and barrier height (ϕ_B), are determined. At the same time, the quantitative analysis of the carrier transport mechanism of MoO₃/n-Si heterojunction was conducted by I–V characteristics curve. The decrease in barrier heights and the subsequent increase in the ideality factor were observed by increasing precursor molarity. Similarly, when the junction exposed to illumination, both the parameters were found to decrease.