Interface-driven modulation of structure and electronic properties in CNT-encapsulated CsPbI <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si16.svg" display="inline" id="d1e473"> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mn>3</mml:mn>

Interfacial engineering is pivotal for tailoring the electronic and optoelectronic properties of low-dimensional materials. In this study, we utilize first-principles density functional theory (DFT) calculations to explore the interface-driven modulation of structural and electronic properties in one-dimensional (1D) halide perovskites, CsPbI 3 and Cs 4 PbI 5 , encapsulated within zigzag carbon nanotubes (CNTs). CsPbI 3 nanowires exhibit semiconducting behavior, with uniaxial strain inducing Fermi level shifts that oppositely modulate the bandgap and carrier mobilities for electrons and holes. In contrast, Cs 4 PbI 5 nanowires display robust metallic behavior, where significant charge transfer to the CNT induces n-type doping. Encapsulation within CNTs fundamentally alters the interfacial physics: for CsPbI 3 , minimal charge transfer occurs, with the CNT serving as a mechanical scaffold that preserves the semiconducting character, while for Cs 4 PbI 5 , strong electronic coupling and substantial charge transfer result in active heterojunction formation. To further tailor these interactions, we investigate boron and nitrogen doping of the CNTs, which modulates the Fermi level, enabling precise control over charge transfer and interfacial band alignment, allowing tunable carrier dynamics at the perovskite-CNT interface. These findings provide critical insights for designing perovskite-based nanoelectronic and optoelectronic devices with engineered interfacial functionalities.