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

Abstract 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 Cs 2 NaInCl 6 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 Cs 2 NaInCl 6 DPs exhibit blue PL at ≈445 nm and yellow PL at ≈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 .