Biexciton Quantum Yield of Single Semiconductor Nanocrystals from Photon Statistics

Abstract

Biexciton properties strongly affect the usability of a light emitter in quantum photon sources and lasers but are difficult to measure for single fluorophores at room temperature due to luminescence intermittency and bleaching at the high excitation fluences usually required. Here, we observe the biexciton (BX) to exciton (X) to ground photoluminescence cascade of single colloidal semiconductor nanocrystals (NCs) under weak excitation in a g(2) photon correlation measurement and show that the normalized amplitude of the cascade feature is equal to the ratio of the BX to X fluorescence quantum yields. This imposes a limit on the attainable depth of photon antibunching and provides a robust means to study single emitter biexciton physics. In NC samples, we show that the BX quantum yield is considerably inhomogeneous, consistent with the defect sensitivity expected of the Auger nonradiative recombination mechanism. The method can be extended to study X,BX spectral and polarization correlations.

Magneto-optical properties of trions in non-blinking charged nanocrystals reveal an acoustic phonon bottleneck

“…Photon-correlation measurements under pulsed excitation (Fig. 1f) show that the charged biexciton is highly efficient (B80%) indicating that the emission from both trion charge species is efficient 31 . This suggests that the main NC ionization pathway is not Auger assisted 28 , but most likely a tunnelling process and hence dependent on the shell and surface properties.…”

Cryogenic single nanocrystal spectroscopy: reading the spectral fingerprint of individual CdSe quantum dots

“…If the bi-exciton emission is efficient, the temporal signature of a biexciton-exciton radiative cascade will show up in the zero delay peak. For single NCs with unity quantum yield for exciton emission 53 the biexciton quantum yield can be directly determined from the ratio of of the central peak to the lateral one 49 . In Fig.…”

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

“…In Fig. 6d we show a second order photon correlation measurement conducted at 140 K and in the weak pump regime, where the signal is directly proportional to the biexciton efficiency 49 . In these conditions, the ratio of the central peak to a lateral one directly yields a biexciton quantum efficiency of ~80% for this NC.…”