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–Bi₂O₃/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 ∼15nm, assembled into a three-dimensional sponge-like morphology composed of interconnected nanoparticles with an overall diameter of ∼220nm. This hierarchical structure enables efficient light trapping and charge transport pathways. Optical characterization demonstrates strong and continuous absorption across the ultraviolet–visible region (250–700nm), with an optimized optical bandgap of 1.84eV, 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 0.07×10⁸ Jones at 3.6eV, accompanied by stable and reproducible operation. The combination of heterophase band alignment, conjugated polymer coupling and sponge-like nanoarchitecture endows the BiOCl–Bi₂O₃/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.