Probing the Charge Carrier Dynamics in Thermoelectric Properties of Quasi 2D Phonon-Glass Electron-Crystal Ruddlesden–Popper Perovskites

Ruddlesden–Popper perovskite oxides are a promising class of semiconductors for thermoelectric applications due to the confinement of phonons between the layers. However, the structural aspect of these materials favors the formation of slow-moving self-trapped charge carriers, resulting in slow charge transport. In this work, we investigate the key aspects of small polaron transport in two perovskites La2CoO4 and LaSrCoO4 with the help of experimental characterizations such as thermopower and resistivity measurements. Further, electrical transport analysis reveals that conduction is governed by the small polaron hopping theory with weighted mobility on the order of 10–3 and 10–2 cm2 V–1 s–1, respectively. The calculated electron–phonon coupling strength (γP = 20, 26), polaron binding energy (EP = 543, 746.8 meV), and polaron effective mass (4.33, 5.33 me*) of La2CoO4 and LaSrCoO4 reveal the existence of robust electron–phonon coupling in Ruddlesden–Popper perovskites, which facilitates the creation of small polarons.