A flexible luminescence film with temperature and infrared response based on Eu2+/Dy3+ co-doped Sr2Si5N8 phosphors for optical information storage applications

Abstract

Deep-trap luminescent materials have attracted great attention for optical information storage applications. However, the flexible luminescence films based on red luminescence materials with temperature and infrared response are scarce. In this study, we have successfully developed various novel flexible red emitting films based on Eu²⁺/Dy³⁺ co-doped Sr₂Si₅N₈ phosphors through screen-printing and spin-coating technologies, respectively. Interestingly, the fabricated flexible luminescence films exhibit unique temperature and infrared responsive properties for optical information storage by releasing photons in response to thermal or infrared stimulation. Notably, deep-trap red emitting Eu²⁺/Dy³⁺ co-doped Sr₂Si₅N₈ phosphors are crucial for the optical information storage properties of the films. Two emission peaks of Sr₂Si₅N₈:Dy³⁺ phosphors at 476 nm and 577 nm are observed under excitation at 345 nm, corresponding to the radiative transition occurs from the ⁴F_9/2 level to the ⁶H_13/2 and ⁶H_15/2 levels of Dy³⁺. When Dy³⁺ and Eu²⁺ ions are co-doped in Sr₂Si₅N₈, the energy transfer from Dy³⁺ to Eu²⁺ in Sr₂Si₅N₈ matrix is found and the decay time confirms that Dy³⁺ ions can be acted as deep trap centers to storage photons. For Sr₂Si₅N₈:Eu²⁺,Dy³⁺ phosphors and the corresponding flexible luminescence films, the specific patterns (for example apple and note patterns) are firstly recorded under NUV or blue light excitation and then reappear through thermal stimulation or near-infrared photo-stimulation (980 nm laser). This work not only validates the feasibility of Sr₂Si₅N₈:Eu²⁺,Dy³⁺ phosphors as deep-trap red emitting luminescence materials, but also suggests the applications of flexible luminescence films for optical information storage.

Keywords: Advanced optical materials; Optical information storage; Sr2Si5N8; Trap engineering.