MWCNT-Bridged Interface Engineering of Stable Lead-Free Hybrid Perovskites with Enhanced Charge Transport as Promising Next-Generation Photovoltaic Absorbers

Developing nontoxic, stable, high-performance photovoltaic materials remains a key challenge for solar technology. Here, we report a composition-engineered 1D–2D hybrid heterojunction of Multi-Walled Carbon Nanotubes (MWCNTs) integrated with Lead-free Copper-based perovskites. This report investigates a significant reduction in bandgap values up to 1.56 eV and an Urbach energy of 121 meV for the MWCNT-NCuP composite, which is evidenced by dielectric properties, AC conductivity, and electric modulus studies conducted in the temperature and frequency ranges of 303–423 K and 102 Hz–106 Hz providing valuable insights into its suitability for photovoltaic applications. The observed high dielectric constant (∼108) facilitates efficient exciton dissociation by diminishing Coulombic interactions. AC conductivity increases from ∼10–2 to ∼101 S/cm when compared to pristine perovskite in our previous report. One of the composites, MWCNT-NCuP, shows a significant enhancement of 11.6-fold in AC conductivity from 6.615 × 10–1 to 7.6825 S/cm at 104.6 Hz. With temperature, conductivity increases significantly, indicating thermally activated transport. The incorporation of MWCNTs enhances both the dielectric constant and conductivity due to improved interfacial charge transfer and mobility, all of which are supported by Powder-XRD, UV–Vis–NIR, PL, FE-SEM, and HR-TEM results. Electrochemical behavior shows a significant enhancement of current response. Stability analysis done in the time period of 90 days revealed superior environmental stability evidenced by P-XRD, FE-SEM, and TGA analysis. Even though our previously reported visible thermochromism of perovskites is suppressed, the underlying thermally induced processes within the material remain active; the suppression of thermochromism, rather than being a drawback, provides a controllable pathway to design multifunctional coatings where thermal, optical, and electrical properties can be balanced for advanced sensing and energy applications. Altogether, the MWCNT-perovskite heterojunction possesses superior structural, optical, electrical, and stability features, directly explaining its enhanced photovoltaic performance. MWCNT inclusion has been extensively researched in Lead-free perovskites, whereas MWCNT-Copper-based Nickel-doped perovskite has not yet reported.