Surface ligation stage revealed through polarity-dependent fluorescence during perovskite nanocrystal growth

Abstract

Selective, polarity-based filtration of a reaction mixture during growth was used to track surface ligation during nanocrystal growth.

Evolving Stark Effect During Growth of Perovskite Nanocrystals Measured Using Transient Absorption

“…Likewise, the fluorescence spectrum began to lose intensity at shorter wavelengths while the peak at 635 nm continued to grow and redshift until the final measured timepoint. The evolution of these spectra are in agreement with previously reported experiments performed under similar conditions (Sadighian et al, 2019(Sadighian et al, , 2020.…”

“…Using differential measurement, the probe then reports the effect of an ensemble of these electric fields on the absorption of the NC sample. These findings agree with previous reports of the growth mechanism of CdSe (Teunis et al, 2017) and MAPbI 3 (Sadighian et al, 2020) NCs, and open up a new avenue for studying the surface of these materials during growth.…”

“…measurements indicate that poorly-capped NCs are dominant during the growth of perovskite NCs, becoming progressively better capped as the growth process continues, similar to the case shown in Figure 1B. Future studies using different polarities of filter media to separate well-and poorly-capped NCs (Sadighian et al, 2020) will seek to test this assumption and further isolate the evolving lineshapes of these sub-populations within the reaction mixture. As demonstrated here by the intriguing trends in the weights of the two derivative features, the ability of SSTA to measure lineshapes during a NC synthesis provides a new avenue to deeper insights into how NCs grow.…”

“…Recently, use of a solvationmediated synthesis (Wang et al, 2017), coupled to a rapid sampling technique (Sadighian et al, 2019), permitted the measurement of linear absorbance and fluorescence during growth. This study revealed that NCs initially grow in size while their surfaces remain poorly-capped by passivating ligands, and do not become well-capped until they are almost fully grown (Figure 1) (Sadighian et al, 2020). Visible absorbance and fluorescence measurements report on transitions from the ground and emissive band-edge states, respectively.…”

“…MAPbI 3 NCs were synthesized using a previously reported solvation-limited synthesis (Sadighian et al, 2019(Sadighian et al, , 2020. 460 mg of PbI 2 and 127 mg of MAI were combined with 40 mL of hexane in a glass test tube and suspended in an ultrasonication bath (VWR, 97043-992) to provide constant mixing.…”