Electronic and Interfacial Properties of 2D MXene/Blue Phosphorene Heterostructures: Impact of External Strain for Thermoelectric Applications

Building two-dimensional (2D) van der Waals (vdW) heterostructures and enhancing their properties through strain engineering unlocks new applications for their constituent materials. In this study, we present a comprehensive first-principles investigation of oxygen-functionalized MXene-based heterostructures (M2CO2/blue phosphorene (blueP), M = Sc, Zr, Hf), emphasizing their structural, electronic, and thermoelectric properties under the application of various types of strain. Our results indicate a reduction in band gap under strain and metallic transition for in-plane strain (uni- and biaxial strain). Transition from type-I to type-II could be obtained for Hf2CO2/blueP and Zr2CO2/blueP heterostructures by applying strain, providing a method for their potential application in photocatalytic devices that require type-II band alignment for photogenerated charge separation. We observe a positive correlation between strain and thermoelectric efficiency under most conditions with a significant enhancement in the thermoelectric power factor (PF) and electronic figure of merit (ZTe) achievable in all heterostructures through strain engineering. Among the three heterostructures, Sc2CO2/blueP showed the maximum PF and ZTe of 11.2 × 1011 W/m K2 s and 43.2 for 2% normal compressive strain and 4% biaxial compressive strain, respectively. These findings suggest that MXene/blueP heterostructures hold significant promise for applications in optoelectronics and high-temperature thermoelectric devices.