Facet-Engineered Rubidium Lead Halide Nanocrystals for Pyro-Phototronic Broadband Photodetection

Cesium lead halide has been extensively studied as efficient materials for optoelectronic device applications. Beyond Cs(I), the exploration of other inorganic A-site monovalent cations remains limited, though Rb(I) stands out as a potential alternative whose role in colloidal nanocrystals is largely unexplored. Here, Rb (I) is employed as an effective A-site cation in forming monoclinic-phase RbPb₂Cl₅, where Pb (II) heptahedrally coordinated. A template-mediated cation exchange strategy is employed where 0D Rb₄CdCl₆ used as host nanocrystals. Upon introduction of Pb (II), fast Cd to Pb ion exchange triggers and 2D RbPb₂Cl₅ in rhombic prism, hexagonal prism or hexagonal platelet-shaped nanocrystals are formed depending on the reaction conditions. Further to explore the optoelectronic properties, photo response measurements are carried out which exhibit significant pyro-photocurrent response from these nanocrystals even under ultra-low-intensity light illumination (7 nW cm^-2) across ultraviolet (UV) to near-infrared (NIR) spectral range. Despite its centrosymmetric structure, RbPb₂Cl₅ generates pyro-photocurrent due to surface halide deficiencies, supported by DFT which shows surface polarization of |𝝙P| = 0.173 C m^-2. These findings highlight the pivotal role of Rb (I) in stabilizing these nanostructures and open a new avenue for their application in advanced optoelectronic devices.