Enhanced upconversion luminescence of UCNPs@CsPbI₃ nanocomposites via constructing multiple energy transfer channels

The application of upconversion nanomaterials relies heavily on the ability to produce bright upconversion luminescence (UCL) or high upconversion quantum yields (UCQYs) at low power density excitation. Herein, we synthesized silica-coated NaYF₄:Yb³⁺@NaGdF₄:Tm³⁺@NaYF₄:Tb³⁺ upconversion nanoparticles (UCNPs) and CsPbI₃ perovskites quantum dots (PeQDs) nanocomposites by the slow hydrolysis of (3-aminopropyl)triethoxysilane. The energy transfer (ET) of Gd³⁺→Tb³⁺ accelerates the five-photon upconversion process of Yb³⁺-Tm³⁺ and the design of the core@shell@shell layer effectively mitigates the energy jumps between Gd³⁺ ions. Importantly, the involvement of multiple ET channels in the UCNPs@CsPbI₃ PeQDs nanocomposites increased the intensity of the UCL on the CsPbI₃ PeQDs by about six times. In addition, the stability of PeQDs encapsulated in a silica matrix under air and water conditions was greatly improved.