Modulating Luminescence of Double Perovskites by Intrinsic Strain Effect and Applications in White Light Emitting Devices

Double perovskite (DP) is considered as a promising candidate for single-component white-light emitters. However, the photoluminescence (PL) efficiency of the small sized DP, such as microcrystals and nanocrystals, is generally unsatisfactory. In this work, by comparing the Sb/Bi co-doped Cs2NaInCl6 microcrystals prepared at different conditions, it is revealed that the PL spectral profile and efficiency are highly dependent on intrinsic strain effect. All the Sb/Bi co-doped Cs2NaInCl6 DPs exhibit blue PL at approximate to 445 nm and yellow PL at approximate to 560 nm. When the crystal size decreases, the release of local strain results in a significant quenching in the emission intensity. Accordingly, by optimizing the reaction conditions to introduce sufficient lattice mismatch, high PL quantum yields (QYs) of 76.38% and 86.44% are obtained for blue and yellow PL, respectively. Moreover, a white light-emitting convertor with a high colour rendering index (CRI) of 90.0 is fabricated, which shows a luminous efficiency of 40.4 lm W-1. Increasing intrinsic strain results in enhanced luminescence intensity and increased quantum yield, highlighting the feasibility to regulate the luminescent properties of double perovskites (DPs) through adjusting the intrinsic strain. By optimizing the reaction conditions to introduce sufficient lattice mismatch, both blue and yellow photoluminescence of Sb/Bi co-doped Cs2NaInCl6 DPs are improved, which can be applied for single-component white light emitters with high efficiency and high color rendering index.image