Highly efficiency blue emissive from Bi3+ ions in zero-dimensional organic bismuth halide for white LED applications

Zero-dimensional organic-inorganic metal halides (OMHs) attract increasing interest in the fabrication of light-emitting diodes because of their broad emission band and high photoluminescence quantum yield. Thus, almost all OMHs showed green and yellow emissions, while blue was rarely reported. The luminescence mechanism of OMHs was attributed to the self-trapped excitons (STEs), no matter the similar performances between STEs and translations from energy levels of ns ² ions (Sb ³⁺, Bi ³⁺, and Te ⁴⁺ ions). In this work, zero-dimensional organic tetraphenylphosphonium bismuth chloride TPP ₂BiCl ₅ (C ₄₈H ₄₀P ₂BiCl _5, abbreviated as TBC, TPP=tetraphenylphosphonium.) was synthesized via the antisolvent method The obtained TBC showed the highest efficiency (58%) in blue light emission at 480 nm. While most of the OMHs function according to the STE mechanism, the emission of TBC was confirmed to originate from the ³P ₁- ¹S ₀ transition of Bi ³⁺ ions. The white light-emitting diodes (WLEDs) with a color rendering index of 81 were fabricated by using a near-ultraviolet (NUV) chip, blue emitting single crystal TBC, green-emitting single crystal TPP ₂MnCl ₄ (C ₄₈H ₄₀P ₂MnCl ₄, abbreviated as TMC), and red-emitting single crystal TPP ₂SbCl ₅ (C ₄₈H ₄₀P ₂SbCl ₅, abbreviated as TSC). Moreover, the single-component white emission was achieved by doping Mn ²⁺ and Sb ³⁺ ions into the lattice of TBC. This work demonstrates the different emission mechanism of ns ² ions based OMHs, and the great potential of bismuth-based OMHs in the applications of WLEDs.