Efficient Near-Infrared Phosphors Discovered by Parametrizing the Eu(II) 5d-to-4f Energy Gap

Summary Inorganic materials with rare-earth activators (e.g., Ce, Eu) exhibit broad 5d-to-4f emission spectra characterized by a strong host material dependency. Despite extensive research, the development of an efficient and near-infrared (NIR) 5d-to-4f emission remains elusive. Herein, we introduce key descriptors of the Eu(II)-host interactions and predict the in-crystal 5d-to-4f energy gap with a root-mean-square error of ca. 0.03 eV (7.0 nm). By incorporating this luminescence predictor into a high-throughput screening of 223 nitride materials in the Inorganic Crystal Structure Database, we identify and experimentally validate (Sr,Ba)3Li4Si2N6:Eu(II) with NIR emissions of {$\lambda$}em = 800 {$\sim$} 830 nm and high quantum efficiencies (QEs) of 30\% {$\sim$} 40\%, leading to an NIR light power {$\sim$}3\texttimes{} superior to prevailing NIR emitters. The ultralong {$\lambda$}em and high QE stem from a coordinated energy transfer and an optimized electronic delocalization around Eu(II). This work provides a cost-efficient computational approach for discovering phosphors with desired emissions.