Organic Semiconducting Ligands Passivated CsPbBr₃ Nanoplatelets for Blue Light-Emitting Diodes

Metal halide perovskite nanocrystals have shown tremendous potential for application in light-emitting diodes (LEDs) due to their unique and remarkable optoelectronic properties. Here, we report the development of CsPbBr 3 nanoplatelets (NPLs) with surface passivation by organic semiconducting ligands for blue LEDs. The use of two organic salts, triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium sulfate (TPPcarz 2 SO 4 ) and triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium bromide (TPPcarzBr), as surface treatment agents allows for the preparation of 300 nm size CsPbBr 3 NPLs with a blue emission peaked at 455 nm and a photoluminescence quantum efficiency (PLQE) of 82%. Moreover, the charge-transporting TPPcarz + units improve the conductivity of thin films based on CsPbBr 3 NPLs and the band edge alignments for blue LEDs. As a result, blue LEDs based on these CsPbBr 3 NPLs exhibit high external quantum efficiencies (EQEs) of up to 4.15%, a maximum luminance of 1511 cd m –2, and a half-lifetime of 50 min (at 100 cd/cm 2 ).