Synthesis and temperature-dependent photoluminescence of CsPbX 3 @SiO 2 (X = Cl, Br, I and their mixtures) nanocrystal films

In this work, we synthesized CsPbX 3 @SiO 2 (X = Cl, Br, I and their mixtures) nanocrystal (NC) films on glass substrates by a centrifugally casting process combining with a surface passivation technique using 3-aminopropyl triethoxysilane (APTES) ligand. The obtained CsPbX 3 @SiO 2 (X = Cl, Br, I and their mixtures) NC films exhibited a cubic structure and stronger PL properties, particularly CsPbBr 3 @SiO 2 NC films with PLQY of 94.1%. Temperature-dependent steady-state and transient PL measurements were performed to systematically investigate the lattice and exciton decay dynamics process from 80K to 300K. It is found that the lattice thermal expansion and the electron-phonon interaction determine the variation of the photon energy and the full width at half maximum (FWHM) of PL bands, and higher exciton activation energies are obtained from the dependence of the spectral intensities with temperature. By analyzing the transient PL emission of CsPbX 3 @SiO 2 (X = Cl, Br, I and their mixtures) NC films, the increasing fluorescence decay lifetime with temperature could be attributed to the relaxation and recombination process of excitons trapped by surface states, while the extension of the average lifetime after passivation could stem from the effect of surface ligands by suppressing the non-radiative recombination and prolonging the survival time of charge carriers, which results in the PLQY enhancement of perovskite NC films. Finally, after evaluating the stability of CsPbX 3 @SiO 2 (X = Cl, Br, I and their mixtures) NC films, they were applied in white LED devices with excellent optical and color performances comparable to the white LED device on the market.