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Self-trapped excitons (STEs) have garnered significant attention due to their broadband emission and large Stokes shift. However, achieving multiband, particularly near-infrared (NIR) STE emissions remains a challenge, restricting their optoelectronic applications. Herein, we realize efficient dual-band STE emissions encompassing blue and NIR regions based on Cs 2 NaScCl 6 double perovskites (DPs) via minor Li + -doping structural engineering. The dual-band emissions in the blue and NIR regions originated from the STE states associated with ScCl 6 3– and NaCl 6 5– octahedra, respectively. Li + doping markedly enhanced the photoluminescence (PL) quantum yields of dual-band STE emissions from 3.2% and 2.7% to 98.2% and 45.4%, respectively. Steady-state/transient PL spectroscopies and density functional theory calculations revealed that Li + doping intensified sublattice distortion and enhanced charge carrier localization within Cs 2 NaScCl 6 DPs, thus boosting the dual-band STE emissions. These findings gain deep insights into STE manipulation in DPs through local structural engineering, thus stimulating the exploitation of DPs toward versatile applications.
Liu et al. (Fri,) studied this question.