Creating chromaticity palettes and identifying white light emitters through nanocrystal megalibraries

Halide perovskites are used to fabricate energy-efficient optoelectronic devices. Determining which compositions yield desired chromatic responses is challenging, especially when doping strategies are used. Here, we report a way of mapping the compositional space of halide perovskites to generate a light emission or "chromaticity" palette. Megalibraries consisting of millions of Mn²⁺-doped PEA₂PbX₄ (PEA: phenethylammonium, X: halide anions) perovskite nanocrystals were synthesized to screen the compositions that led to specific emission profiles. The chromaticity palette allows one to identify single-composition white light emitters [PEA₂Pb_1-Mn(Br_1-I)₄ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1)], eliminating the need for trilayer structures in conventional white light-emitting diodes, which are prone to instability and complex device designs. Optical studies reveal that the dual-wavelength photoluminescence emission originates from exciton recombination and energy transfer processes. This study shows how emerging megalibrary capabilities can rapidly advance our understanding of the complex composition-structure-function relationships and be used to accelerate the discovery of next-generation optoelectronic materials.