Possible Charge-Transfer-Induced Conductivity Enhancement in TiO₂ Microtubes Decorated with Perovskite CsPbBr₃ Nanocrystals

Halide perovskite CsPbBr₃ quantum dots (QDs) were synthesized via supersaturated recrystallization process and deposited on the surface of TiO₂ microtubes forming local nano-heterostructures. Structural, morphological, and optical characterizations confirm the formation of heterostructures comprised of TiO₂ microtube decorated with green-emitting CsPbBr₃ nanocrystals. Optical characterizations reveal the presence of two band gap energies corresponding to CsPbBr₃ (2.34 eV) and rutile-TiO₂ (2.97 eV). Time-resolved photoluminescence decays indicate different charge dynamics when comparing both samples, revealing the interaction of CsPbBr₃ QDs with the microtube surface and thus confirming the formation of local nano-heterostructures. The voltage-current measurements in the dark show an abrupt decrease in the electrical resistivity of the CsPbBr₃/TiO₂ heterostructure reaching almost 95% when compared with the pristine TiO₂ microtube. This significant increase in the electrical conductivity is associated with charge transfer from perovskite nanocrystals into the semiconductor microtube, which can be used to fine tune its electronic properties. Besides controlling the electrical conductivity, decoration with semiconducting nanocrystals makes the hollow heterostructure photoluminescent, which can be classified as a multifunctionalization in a single device.