In Situ Colloidal Growth of Cs3Sb2I9/CsI Heteronanocrystals with Interfacial Charge Regulation for Broadband Photodetection and Virtual Imaging

Abstract We develop a single-injection in situ colloidal growth strategy for constructing Cs3Sb2I9/CsI heteronanocrystals, in which CsI nanocrystals directly nucleate on Cs3Sb2I9 domains within a single reaction process. Systematic regulation of the growth conditions enables control over the CsI loading and heteronanocrystal morphology, demonstrating the kinetically tunable evolution of the coupled nanostructure. The shared Cs–I-based ionic structural motifs may facilitate intimate interfacial contact between the two components. Ultraviolet photoelectron spectroscopy (UPS) measurements and density functional theory (DFT) calculations reveal a Type-II band alignment, interfacial charge redistribution, and a built-in electric field at the Cs3Sb2I9/CsI interface, while the calculated negative binding energy confirms the thermodynamic favorability of the coupled interface. These interfacial electronic features promote directional carrier separation and transport, enabling the Cs3Sb2I9/CsI heteronanocrystal-based photodetector (PD) to achieve broadband photoresponse from 405 to 1060 nm, an enhanced Ilight/Idark ratio, and stable operation over 10,000 s. Furthermore, spatially resolved photocurrent mapping enables virtual imaging, highlighting the potential of in situ interface engineering in lead-free halide heteronanocrystals for optoelectronic applications.