Enhancing room temperature thermoelectric efficiency in zigzag phosphorene nanoribbon junctions through Quasi-Flat impurity bands

Abstract In this study, a novel approach has been utilized to Please specify the corresponding author.explore the room temperature thermoelectric properties of zigzag phosphorene nanoribbon-based monolayer-bilayer-monolayer junctions. To achieve thermoelectric properties at room temperature, a quasi-flat energy band with limited width is required. It has been demonstrated, for the first time, that such bands can be observed by considering a junction of the monolayer and bilayer phosphorene nanoribbons. By adjusting the ribbon widths, quasi-flat bands are produced. This geometrical problem is solved using analytical calculations for a general system and applied to phosphorene. We show that the edge states of phosphorene resemble a one-dimensional tight-binding system, with a close agreement between their results. Using the introduced approach, we calculate the electronic energy band structure of the specified system. Initially, we demonstrate that the formation of zigzag monolayer-bilayer-monolayer junctions can lead to the emergence of quasi-flat impurity bands within the energy bandgap. Furthermore, we show that utilizing these structures at room temperature, across a wide range of lead temperature differences, results in significant output electrical power and improved thermoelectric efficiency. The electrical power and thermoelectric efficiency are examined as functions of applied bias voltage and average chemical potential. Additionally, we explore how the output electrical power, thermoelectric efficiency, and efficiency at maximum power vary with the temperature difference between the leads at the ends of the structure.