Investigation on Cu2MgSnS4 thin film prepared by spray pyrolysis for photovoltaic and humidity sensor applications

In the present work, Cu2MgSnS4 (CMTS) films are deposited by spray pyrolysis technique. The impact of magnesium concentration during the synthesis of CMTS films is studied. Structural, morphological, optical, electrochemical and electrical properties are analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectroscopy, electrochemical impedance spectroscopy (EIS) and I-V characterizations. CMTS films grown with various magnesium concentrations, [Mg] = 3, 5, 7 and 9 mM, show kesterite structure with a preferential orientation along (112) plane. XRD patterns show the appearance of Cu2S and Sn2S3 secondary phases for the majority of Mg concentrations. Contrary, MgS appears only for the highest Mg concentration. The best crystalline quality and highest crystallite size are obtained for [Mg] = 5 mM sample. Surface morphology of CMTS films reveals homogenous and continuous surface for [Mg] = 5 mM. The film thickness varies in very sensitive way with Mg concentration. Optical properties of CMTS reveal a high absorption coefficient in the visible range. A band gap narrowing from 1.56 eV to 1.50 eV with the increase of Mg concentration till 5 mM is noticed, whereas a band gap widening takes place for further increase of Mg concentration. The optimum value of 1.50 eV is obtained at [Mg] = 5 mM which is suitable for solar cell applications. Electrical analysis exhibits a good electrical conductivity at [Mg] = 5 mM and the I–V characteristic indicates an ohmic behavior and high current value of 10−2 A at 4 V under illumination. These properties make CMTS a potential candidate for solar cell applications as well as humidity sensing.