Highly Luminescent and Phase-Stable Red/NIR-Emitting All-Inorganic and Hybrid Perovskite Nanocrystals

Because of their low band gap, iodide-based lead halide perovskite nanocrystals (NCs) with generic formula APbI3 [A = Cs+, methylammonium (MA+), and formamidinium (FA+)] are most suitable for solar photovoltaic applications. However, because of their poor phase stability, obtaining these NCs with stable red/NIR emission is a challenging task and is termed the "red wall". We report here a generic protocol for direct synthesis of all three NCs with extraordinary characteristics employing 1,3-diiodo-5,5-dimethylhydantoin (DIDMH) as iodide precursor. The as-synthesized NCs are phase-pure and monodispersed, and they exhibit phase stability for several months in ambient conditions and photoluminescence quantum yield (PLQY) of near-unity for the red-emitting CsPbI3 NCs and ∼74 ± 2% and 67 ± 2% for NIR-emitting (MA)PbI3 and (FA)PbI3 NCs, respectively. The results highlight the greater efficacy of DIDMH over other iodide precursors, with which the present task could not be achieved earlier. The high-quality NCs for the red–NIR region may be useful for developing efficient perovskite-based solar photovoltaic devices.