Organic Semiconducting Ligands Passivated CsPbBr<sub>3</sub> Nanoplatelets for Blue Light-Emitting Diodes
He Liu, Tunde Blessed Shonde, Oluwadara Joshua Olasupo, Md. Sazedul Islam, Tarannuma Ferdous Manny, Maxim Woodhouse, Xinsong Lin, J. S. Raaj Vellore Winfred, Keyou Mao, Eric Lochner, Iqra Fatima, Kenneth Hanson, Biwu Ma
Abstract
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 ).