W-Doped Cs₂SnCl₆ for Near-Infrared Emission

0D perovskite derivatives such as Cs₂WCl₆ and Cs₂WO_<i>x</i>Cl_6-<i>x</i> have been recently shown to emit near-infrared (NIR) radiation. The <i>d</i>-<i>d</i> electronic transition of W⁴⁺/W⁵⁺ yields an NIR emission. However, the close proximity of those ions can quench the photoluminescence via concentration quenching. To address this issue, here we dilute the emission centers by doping a small amount of W into the Cs₂SnCl₆ 0D perovskite. The results suggest that the dopant centers are [WOCl₅]^2- replacing [SnCl₆]^2- octahedra in the host lattice. The optimal 3.3% W-doped Cs₂SnCl₆ exhibits NIR (965 nm) emission with over 52 times higher intensity compared to that of Cs₂WO_<i>x</i>Cl_6-<i>x</i>. The suppression of concentration quenching in W-doped Cs₂SnCl₆ also significantly alters its temperature-dependent (7-300 K) photoluminescence compared to that of Cs₂WO_<i>x</i>Cl_6-<i>x</i>. Finally, we demonstrated NIR phosphor-converted light-emitting diodes of W-doped Cs₂SnCl₆ showing an output power of 10.3 mW at 400 mA. This is the first report of W doping in 0D perovskites showing its potential as an NIR phosphor.