Probing the Charge\nCarrier Dynamics in Thermoelectric\nProperties of Quasi 2D Phonon-Glass Electron-Crystal Ruddlesden–Popper\nPerovskites

Ruddlesden–Popper perovskite oxides are a promising\nclass\nof semiconductors for thermoelectric applications due to the confinement\nof phonons between the layers. However, the structural aspect of these\nmaterials favors the formation of slow-moving self-trapped charge\ncarriers, resulting in slow charge transport. In this work, we investigate\nthe key aspects of small polaron transport in two perovskites La<sub>2</sub>CoO<sub>4</sub> and LaSrCoO<sub>4</sub> with the help of experimental\ncharacterizations such as thermopower and resistivity measurements.\nFurther, electrical transport analysis reveals that conduction is\ngoverned by the small polaron hopping theory with weighted mobility\non the order of 10<sup>–3</sup> and 10<sup>–2</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, respectively.\nThe calculated electron–phonon coupling strength (γ<sub>P</sub> = 20, 26), polaron binding energy (<i>E</i><sub>P</sub> = 543, 746.8 meV), and polaron effective mass (4.33, 5.33 <i>m</i><sub>e</sub><sup>*</sup>) of La<sub>2</sub>CoO<sub>4</sub> and LaSrCoO<sub>4</sub> reveal\nthe existence of robust electron–phonon coupling in Ruddlesden–Popper\nperovskites, which facilitates the creation of small polarons.