Mixed Ligand Passivation as the Origin of Near-Unity Emission Quantum Yields in CsPbBr₃ Nanocrystals

Abstract

Key features of syntheses, involving the quaternary ammonium passivation of CsPbBr3 nanocrystals (NCs), include stable, reproducible, and large (often near-unity) emission quantum yields (QYs). The archetypical example involves didodecyl dimethyl ammonium (DDDMA+)-passivated CsPbBr3 NCs where robust QYs stem from interactions between DDDMA+ and NC surfaces. Despite widespread adoption of this synthesis, specific ligand–NC surface interactions responsible for large DDDMA+-passivated NC QYs have not been fully established. Multidimensional nuclear magnetic resonance experiments now reveal a new DDDMA+-NC surface interaction, beyond established “tightly bound” DDDMA+ interactions, which strongly affects observed emission QYs. Depending upon the existence of this new DDDMA+ coordination, NC QYs vary broadly between 60 and 85%. More importantly, these measurements reveal surface passivation through unexpected didodecyl ammonium (DDA+) that works in concert with DDDMA+ to produce near-unity (i.e., >90%) QYs.

Resonant Multiple-Phonon Absorption Causes Efficient Anti-Stokes Photoluminescence in CsPbBr3 Nanocrystals

“…Quaternary ammonium passivated CsPbBr 3 NCs were synthesized via literature procedures. , Benzoyl bromide was introduced to premade Cs–Pb-oleate to trigger NC growth. Particles were subsequently passivated with didodecyl dimethylammonium bromide (DDDMABr), washed with ethyl acetate, and redispersed in toluene.…”

Investigations on the Strong Light-Changed Photoluminescence Performance and the Crystalline Structure of MAPbBr1Cl2 Mixed Halide Perovskites

“…TlPbI 3 also exhibits a sensitive photoresponse with a photocurrent/dark current ratio of approximately 80:1 . Moreover, CsPbBr 3 and (NH 4 ) 3 Bi 2 I 9 perovskites demonstrate impressive sensitivity as X-ray detectors. − Peng et al synthesized colloidal CsPbBr 3 nanocrystals with a high photoluminescence quantum yield (PLQY) of 93.8 ± 1.3%. ,, Sun et al found that doping 2.8% Ni into the CsPbCl 2.4 Br 0.6 lattice can significantly increase the PLQY from 1.2 to 92.0%. , Additionally, the field of perovskite lasing has underwent rapid development since the discovery of ultralow-threshold room-temperature amplified spontaneous emission (ASE) and lasing from CH 3 NH 3 PbX 3 . − …”

“…26−28 Peng et al synthesized colloidal CsPbBr 3 nanocrystals with a high photoluminescence quantum yield (PLQY) of 93.8 ± 1.3%. 10,16,29 Sun et al found that doping 2.8% Ni into the CsPbCl 2.4 Br 0.6 lattice can significantly increase the PLQY from 1.2 to 92.0%. 30,31 Additionally, the field of perovskite lasing has underwent rapid development since the discovery of ultralow-threshold room-temperature amplified s p o n t a n e o u s e m i s s i o n ( A S E ) a n d l a s i n g f r o m CH 3 NH 3 PbX 3 .…”

Synergistic Surface Modification for High‐Efficiency Perovskite Nanocrystal Light‐Emitting Diodes: Divalent Metal Ion Doping and Halide‐Based Ligand Passivation

“…[4,[22][23][24] Of these, didodecyldimethylammonium halide (DDAX, X = F, Cl, Br, I) ligands have been successfully demonstrated to increase the efficiency of LEDs by passivating the PNC surface. [25][26][27] On the other hand, a B-site engineering strategy with divalent metal dopant cations has successfully been used to control B-site vacancies stabilize surface, and reduce the defect density of PNCs, where the divalent metal ions are known to strengthen the bonding with surface ligands and prevent the desorption of organic ligands. [28,29] In particular, the incorporation of small B-site cations such as Cd 2+ has been shown as a strategy to better accommodate the relatively large quaternary ammonium ligands by partially distorting the near-surface [MX 6 ] [4]− octahedra to render large-sized A-site vacancies, providing us with an interesting example of how the A-and B-site species can effectively influence each other during passivation.…”

“…[ 4,22–24 ] Of these, didodecyldimethylammonium halide (DDAX, X = F, Cl, Br, I) ligands have been successfully demonstrated to increase the efficiency of LEDs by passivating the PNC surface. [ 25–27 ]…”