Benzyl Alcohol-Treated CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> Nanocrystals Exhibiting High Luminescence, Stability, and Ultralow Amplified Spontaneous Emission Thresholds.

Veldhuis, Sjoerd A; Tay, Yong Kang Eugene; Bruno, Annalisa; Dintakurti, Sai S H; Bhaumik, Saikat; Muduli, Subas Kumar; Li, Mingjie; Mathews, Nripan et al. · Nano Lett · 2017

basic_science · Level V

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Abstract

We report the high yield synthesis of about 11 nm sized CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> nanocrystals with near-unity photoluminescence quantum yield. The nanocrystals are formed in the presence of surface-binding ligands through their direct precipitation in a benzyl alcohol/toluene phase. The benzyl alcohol plays a pivotal role in steering the surface ligands binding motifs on the NC surface, resulting in enhanced surface-trap passivation and near-unity PLQY values. We further demonstrate that thin films from purified CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> nanocrystals are stable >4 months in air, exhibit high optical gain (about 520 cm<sup>-1</sup>), and display stable, ultralow amplified spontaneous emission thresholds of 13.9 ± 1.3 and 569.7 ± 6 μJ cm<sup>-2</sup> at one-photon (400 nm) and two-photon (800 nm) absorption, respectively. To the best of our knowledge, the latter signifies a 5-fold reduction of the lowest reported threshold value for halide perovskite nanocrystals to date, which makes them ideal candidates for light-emitting and low-threshold lasing applications.