Sponge-like-shape bismuth oxychloride–bismuth oxide/poly-o-chloroaniline nanocomposite for solar cell-like photon sensing and capture

Efficient photon-sensing materials that combine broad optical absorption with stable charge transport remain central to the development of next-generation optoelectronic devices. Here, we report a core–shell BiOCl–Bi 2 O 3 /poly-o-chloroaniline (POCA) nanocomposite thin film engineered to exhibit solar-cell-like photon sensing and capture behavior. The nanocomposite is fabricated via a facile one-pot strategy, assisted by an ultrathin polypyrrole interlayer that promotes uniform film formation and intimate interfacial contact. Structural analyses reveal a highly crystalline heterophase architecture with an average crystallite size of [Formula: see text]15[Formula: see text]nm, assembled into a three-dimensional sponge-like morphology composed of interconnected nanoparticles with an overall diameter of [Formula: see text]220[Formula: see text]nm. This hierarchical structure enables efficient light trapping and charge transport pathways. Optical characterization demonstrates strong and continuous absorption across the ultraviolet–visible region (250–700[Formula: see text]nm), with an optimized optical bandgap of 1.84[Formula: see text]eV, enabling effective photon harvesting. The resulting optoelectronic device exhibits a pronounced photoresponse at room temperature, with the photocurrent density exceeding the dark current by a factor of two under illumination. Notably, the photoresponse is strongly dependent on photon energy, with enhanced photocurrent, photoresponsivity and detectivity observed at higher excitation energies. The maximum detectivity reaches [Formula: see text] Jones at 3.6[Formula: see text]eV, accompanied by stable and reproducible operation. The combination of heterophase band alignment, conjugated polymer coupling and sponge-like nanoarchitecture endows the BiOCl–Bi 2 O 3 /POCA system with efficient photon capture and sensitive electrical readout. Owing to its low-cost fabrication, structural stability and scalable processing, this nanocomposite represents a promising platform for practical photon sensing and light-harvesting applications.