Fast Charge Extraction in Perovskite-Based Core-Shell Nanowires

Realizing nanostructured interfaces with precise architectural control enables one to access properties unattainable using bulk materials. In particular, a nanostructured interface (e.g., a core shell nanowire) between two semiconductors leads to a short charge separation distance, such that photoexcited charge carriers can be more quickly and efficiently collected. While vapor-phase growth methods are used to synthesize uniform core-shell nanowire arrays of semiconductors such as Si and InP, more general strategies are required to produce related structures composed of a broader range of materials. Herein, we employ anodic aluminum oxide templates to synthesize CH3NH3PbI3 perovskite core copper thiocyanate shell nanowire arrays employing a combination of electrodeposition and solution casting methods. Using scanning electron microscopy, powder X-ray diffraction, and time-resolved photoluminescence spectroscopy, we confirm the target structure and show that adopting a core shell nanowire architecture accelerates the rate of charge quenching by nearly 3 orders of magnitude compared to samples with only an axial junction. Subsequently, we fit decay curves to a triexponential function to attribute fast quenching in core-shell nanowires to charge extraction by the copper thiocyanate nanotubes, as opposed to recombination within the perovskite nanowires. Dramatic improvements to charge extraction speed and efficiency result from the substantially reduced charge separation distance and increased interfacial area achieved via the core shell nanowire array architecture.