Optoelectronic evaluation of SrMnO3 cubic perovskite for prospective visible light solar photovoltaic application

Next-generation solar cell materials with superior optoelectronic and photovoltaic properties must circumvent the toxicity and degradation issues of hybrid lead halide perovskites. In this regard, transition metal oxide perovskites with favourable optoelectronic properties are of significant relevance. In this work, we report a combined theoretical–experimental investigation into the optoelectronic properties of cubic-perovskite, SrMnO₃ (SMO) for prospective visible-light photovoltaic application. Using first-principles density functional theory calculations, we show that SMO with cubic symmetry demonstrates a direct bandgap character (∼0.62 eV), exceptional absorption behaviour (∼10⁵ cm⁻¹ in the visible range), substantial dielectric constant (∼11) and a reasonably small exciton binding energy (∼44 meV) promising a sizeable photovoltaic response (PCE_SLME ∼ 16 %). Accordingly, thin films of SMO were grown on fluorine-doped tin oxide (FTO) coated glass substrate using pulsed laser deposition (PLD) technique. Structural characterization demonstrated phase pure SMO with cubic symmetry. Room-temperature Hall measurement allowed the determination of the nature (p-type) and concentration (1.37 × 10¹² cm⁻³) of majority charge carriers, conductivity (5.56 × 10⁻⁶ S/cm), and carrier mobility (24.5 cm²/V·s) which are reasonably comparable to those of archetypal halide perovskite, CH₃NH₃PbI₃ (MAPbI₃). Ultraviolet photoelectron spectroscopy further allowed the determination of energies corresponding to valence and conduction band edges, crucial for device fabrication. Initial device characterization demonstrates small yet finite photovoltaic response, suggesting the requirement of thorough optimization of the device fabrication parameters and development of a suitable hole transport layer.