Encapsulation of CsPbBr₃ Nanocrystals by a Tripodal Amine Markedly Improves Photoluminescence and Stability Concomitantly via Anion Defect Elimination

Abstract

Photoluminescence of halide perovskite nanocrystals (NCs) quenches rapidly due to ambient instability, inherent trap states, and imperfect ligand–NC passivation. We report a novel synthetic strategy to enhance the stability and eliminate trap states of CsPbBr3 NCs simultaneously by in situ introduction of a tripodal tertiary ammonium bromide ion pair ligand [tris­(2-aminoethyl)­ammonium bromide (TREN·4HBr)]. Tetrabromide ions saturate the PbBr6 octahedra of CsPbBr3 NCs to eliminate the anion vacancies, while TREN with three NH3 + branches enhances efficient encapsulation. TREN·4HBr binds strongly to prevent proton transfer that leads to a facile ligand loss from the NCs surfaces. Ultrafast femtosecond transient absorption kinetics reveals the removal of shallow trap states in the CsPbBr3 NCs leading to a faster carrier recombination to enhance the photoluminescence quantum yield (PLQY). We validate the enhancement in the PLQY by designing light-emitting diodes with an external quantum efficiency of 3.4%. Our work unveils a mechanism for rational improvements of stability and PLQY of CsPbBr3 NCs simultaneously.

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

“…[139] Finally, 1,8-octyldiamine bromide, with two terminal amine functionalities, and tripodal tris(2-aminoethyl) ammonium bromide, with three functional amine groups, have been used to passivate CsPbBr 3 NCs, resulting in an improvement in defect passivation, charge transport, and stability. [199,200] Apart from sterically hindered alkylamines, chiral amines have been utilized in the synthesis of LHP NCs to achieve high circularly polarized luminescence (applications in information storage, asymmetric catalysis, agriculture, and photoelectric devices), where differential emission is achieved upon illumination with left-or right-circularly polarized light. [201,202] Specifically, circularly polarized luminescence can be achieved by inducing chirality in emitters, in this case, through the use of chiral ligands.…”

“…[ 139 ] Finally, 1,8‐octyldiamine bromide, with two terminal amine functionalities, and tripodal tris(2‐aminoethyl) ammonium bromide, with three functional amine groups, have been used to passivate CsPbBr 3 NCs, resulting in an improvement in defect passivation, charge transport, and stability. [ 199,200 ]…”

Residue analysis of thermally depolymerized phthalaldehyde‐based polymer thin films

“…The investigations began by comparing the XPS analysis of the substrate surface to determine the atmospheric impurities and adventitious carbon content 12‐14 . Silicon and SiGe wafers have native oxides in addition to adventitious carbon on the surface and polymer depolymerization may contribute hydrocarbon residue 15,16 .…”

Size-tunable and stable cesium lead-bromide perovskite nanocubes with near-unity photoluminescence quantum yield

“…These results suggest that the strong bromide excess in these peculiar reaction conditions is the sine qua non requirement for preventing the defects formation in our perovskite NCs. 33,34 On these bases, we explored the possibility of adjusting the synthetic parameters for modulating the size of the perovskite nanoparticles without precluding the achievement of near-unity PLQY NCs.…”