Probing linewidths and biexciton quantum yields of single lead halide perovskite nanocrystals in solution

Cesium lead halide perovskite nanocrystals (PNCs, e.g. CsPbX₃ X=Cl, Br, I) have become one of the most promising nano-material for a plethora of optoelectronic applications such as LEDs, light down-conversion, and low-threshold lasing.[1] Despite their tremendous success, our understanding of the fundamental excited state dynamics in single PNCs is still very limited. Their poor photo-stability has hampered single nanocrystal spectroscopic interrogation, and only a handful of studies - all on the least unstable PNCs in the weak confinement regime - have reported biexciton quantum yields and single PNC emission spectra. [2,3] As a result, the linewidth broadening mechanism, and Auger recombination dynamics - in particular for confined PNCs - remain elusive.

Here we report the first comprehensive spectroscopic survey of single PNCs, including highly confined and blue emitting PNCs previously inaccessible to single NC spectroscopy. Using solution-phase photon-correlation-Fourier spectroscopy (s-PCFS), we gauge the effect of inhomogeneous broadening and identify the single PNC emission linewidths. With anti-bunching measurements in solution (solution-g⁽²⁾) we investigate the biexciton quantum yield in the absence of particle photo-degradation, and under low-flux excitation conditions.[5] For the first time, we identify clear trends in the single NC linewidth and underlying Auger rates with size and halide composition. These results highlight the power of advanced photon-correlation spectroscopy to study nanomaterial photo-physics.

1) L. Protesescu et al. Nano Lett. 2015,15,6.

2) G. Raino et al., ACS Nano, 2016, 10,2485-2490.

3) Y. Park et al., J. Am. Chem. Soc., 2015, 10, 10386-10393.

4) F. Hu et al., ACS Nano., 2015, 9,12, 12410-12416.

5) H.Utzat et al. Nano Lett., 2017, 17, pp 6838–6846.