Evaluation of AA-CVD deposited phase pure polymorphs of SnS for thin films solar cells

Six different thin film solar cells consisting of either orthorhombic (-SnS) or cubic (-SnS) tin(ii) sulfide absorber layers have been fabricated, characterized and evaluated. Absorber layers of either -SnS or -SnS were selectively deposited by temperature controlled Aerosol Assisted Chemical Vapor Deposition (AA-CVD) from a single source precursor. -SnS and -SnS layers were grown on molybdenum (Mo), Fluorine-doped Tin Oxide (FTO), and FTO coated with a thin amorphous-TiOx layer (am-TiOx-FTO), which were shown to have significant impact on the growth rate and morphology of the as deposited thin films. Phase pure -SnS and -SnS thin films were characterized by X-ray diffraction analysis (XRD) and Raman spectroscopy (514.5 nm). Furthermore, a series of PV devices with an active area of 0.1 cm(2) were subsequently fabricated using a CdS buffer layer, intrinsic ZnO (i-ZnO) as an insulator and Indium Tin Oxide (ITO) as a top contact. The highest solar conversion efficiency for the devices consisting of the -SnS polymorph was achieved with Mo ( = 0.82%) or FTO ( = 0.88%) as the back contacts, with respective open-circuit voltages (V-oc) of 0.135 and 0.144 V, and short-circuit current densities (J(sc)) of 12.96 and 12.78 mA cm(-2). For the devices containing the -SnS polymorph, the highest efficiencies were obtained with the am-TiOx-FTO ( = 0.41%) back contact, with a V-oc of 0.135 V, and J(sc) of 5.40 mA cm(-2). We show that mild post-fabrication hot plate annealing can improve the J(sc), but can in most cases compromise the V-oc. The effect of sequential annealing was monitored by solar conversion efficiency and external quantum efficiency (EQE) measurements.