Investigation on spray pyrolyzed RMnO₃ [R = Y, er, Yb] hexamanganite thin films for their suitability in photovoltaics

Recently, ferroelectric-photovoltaics have come under the spotlight as a potential class of materials for application in photovoltaic devices. However, the broad bandgap of these ferroelectric-photovoltaic materials causes them to have modest photocurrents. To overcome this challenge hexamanganites can be used as alternatives to achieve high photovoltaic efficiency as it has a small band gap. Here we present a stable, non-toxic, and cost-efficient hexamanganite RMnO₃ [R = Y, Er, Yb] thin films prepared and optimized by spray pyrolysis technique. The formation of the single phase is confirmed by XRD analysis. Morphological studies show grains are uniform and closely packed and the grain size increases with the decrease in ionic radii of rare-earth ions. From the UV Visible spectroscopic study, narrow optical band gap is observed for the films. With a carrier concentration of around 10⁺¹⁴ cm⁻³, Hall measurements proved that the films are p-type semiconductors. The maximum photoresponse was exhibited in the visible region for YMnO₃ and ErMnO₃ films and in the near IR region for YbMnO₃ films. This research illuminates the exploration of stable oxide semiconductors with a small band gap for the suitability in futuristic solar cells.