Interactions\nbetween Functional Units Inducing the\nEvolution of Electronic Band Structure and Improved Thermoelectric\nPerformance of n‑Type (Bi<sub>2</sub>)<sub><i>x</i></sub>(Bi<sub>2</sub>Te<sub

An\nordered construction of functional units is a promising avenue\nto synergistically optimize the electrical and thermal transport properties\nof superlattices and pseudosuperlattices. Although it is accepted\nthat interlayer interactions between functional units could effectively\nregulate carrier transport parameters, the influence of artificial\nstacking modalities on electronic band structures and thermoelectric\nperformance required in-depth studies. Here, we report the fabrication\nof two batches of n-type (Bi<sub>2</sub>)<sub><i>x</i></sub>(Bi<sub>2</sub>Te<sub>3</sub>)<sub><i>y</i></sub> pseudosuperlattice\nfilms with varying thicknesses and termination surfaces. An obvious\ndownshift of the Fermi level position and a remarkable increase of\nthe electron density were observed in the (Bi<sub>2</sub>)<sub><i>x</i></sub>(Bi<sub>2</sub>Te<sub>3</sub>)<sub><i>y</i></sub> films with rising Bi<sub>2</sub> content, which is attributed\nto the spontaneous electron injection from the Bi<sub>2</sub> layers\nto the Bi<sub>2</sub>Te<sub>3</sub> layers due to their work function\ndifference. By angle-resolved photoemission spectroscopy measurements,\nwe observed rich electronic band structures in Bi<sub>2</sub>-terminated\n(Bi<sub>2</sub>)<sub><i>x</i></sub>(Bi<sub>2</sub>Te<sub>3</sub>)<sub><i>y</i></sub> films, containing two sets\nof band dispersions: one originating from Bi<sub>2</sub>Te<sub>3</sub> and the other from the hybridization of Bi<sub>2</sub> states and\nBi<sub>2</sub>Te<sub>3</sub> states, similar to those reported in\nBi<sub>1</sub>Te<sub>1</sub> and Bi<sub>4</sub>Te<sub>3</sub> superlattices.\nIn contrast, the band dispersions are dominated by the energy bands\nfrom the Bi<sub>2</sub>Te<sub>3</sub> compound when the Bi<sub>2</sub>Te<sub>3</sub> layers are the termination surfaces. Moreover, the\nthinner films showed higher electron density and carrier effective\nmass due to the suppression of p-type Bi<sub>Te</sub> antisite defects.\nFinally, the (Bi<sub>2</sub>)<sub>12</sub>(Bi<sub>2</sub>Te<sub>3</sub>)<sub>6</sub> pseudosuperlattice film achieved the highest power\nfactor of 1.27 mW m<sup>–1</sup> K<sup>–2</sup>, surpassing\nthe performance of pristine Bi<sub>2</sub>Te<sub>3</sub> and Bi films\nas well as other pseudosuperlattices.