High photoluminescence quantum yield near-infrared emission from a lead-free ytterbium-doped double perovskite.

When excited by photons with energies greater than 2.2 eV, the bandgap energy, Yb-doped CsAgBiBr thin films synthesized physical vapor deposition emit strong near-infrared luminescence centered at ∼1.24 eV the YbF → F electronic transition. Robust, reproducible, and stable photoluminescence quantum yields (PLQY) as high as 82.5% are achieved with CsAgBiBr films doped with 8% Yb. This high PLQY indicates facile and efficient energy transfer from the perovskite host, CsAgBiBr, to Yb, making CsAgBiBr the most promising lead-free down-conversion material.