Tuning the p-type conductivity and transparency of perovskite nickelates by configurational entropy

Configurational entropy can have a dominating role in the electrical transport behavior and optical bandgap, thereby playing a crucial role in the development of transparent conductive oxides. Here, single-phase perovskite RNiO3 (RLa, Pr, Nd, Sm, Eu) thin films on Mica substrates using chemical solution deposition were fabricated, with varying configurational entropies (low-, medium- and high-entropy system). The structure, optical and electrical properties have been thoroughly investigated. It is revealed that optical bandgap, carrier mobility and carrier concentration in RNiO3 films depends on the variation of configurational entropy. As configurational entropy increases, carrier mobility decreases due to reduced grain sizes, while the carrier concentration and bandgap increase as a result of metal cations reduction and lattice distortion. Remarkably, a p-type conductivity of 2.3 S/cm and optical transmittance of approximately 50% were achieved in the medium-entropy La0.25Sm0.25Pr0.25Nd0.25NiO3 thin films. This is due to the increased bandgap enhances transparency, while the improved carrier concentration ensures a certain level of conductivity. Furthermore, the La0.25Sm0.25Pr0.25Nd0.25NiO3 thin films demonstrated excellent potential for application in flexible electrodes. These findings confirm that the tuning of transparency and conductivity of perovskite nickelates thin films through configurational entropy is an effective approach to improve the performance of flexible transparent conductive devices.