a, In the conventional photoluminescence (PL) blinking model, ON and OFF periods correspond to a neutral nanocrystal (X⁰) and a charged nanocrystal (X⁻), respectively. b, Schematic photoluminescence decay of the ON and the OFF states on a logarithmic scale. The dynamics of the ON state is dominated by the radiative rate γ_r. In the charged state, the increase in the number of recombination pathways leads to a higher radiative rate, 2γ_r, responsible for the higher emission intensity at short delays. Simultaneously, the onset of three-particle Auger recombination with the rate γ_A  γ_r opens a new, non-radiative, channel, leading to faster photoluminescence decay and reduced photoluminescence quantum yield. c, When the timescale of charging and discharging is longer than the experimental binning time, binary blinking is observed. d, For fluctuations much faster than the bin size, a continuous distribution of intensities and lifetimes is obtained, often referred to as flickering. The insets in c and d show corresponding schematic fluorescence lifetime–intensity distributions (FLIDs).

a, Set-up of a single-nanocrystal spectroelectrochemical experiment. APD, avalanche photodiode; BS, 50/50 beam splitter; ITO, indium tin oxide; TCSPC, time-correlated single-photon counting. b, Series of photoluminescence decays for a single nanocrystal for increasingly negative applied potentials. The thin grey lines show the best global triple-exponential fits with the shared time constants, yielding the lifetimes τ^d = 2 ns, τ^s = 5 ns and τⁿ = 24 ns. Top inset: the second-order photoluminescence intensity correlation function measured for this nanocrystal indicates that g₂(0) = 0.08. Bottom inset: residuals of the global fit indicate very high fidelity of the fitting procedure, with deviations within the noise level and below 1% of the maximum photoluminescence signal.

a, Photoluminescence intensities (black lines) and average lifetimes (red lines), and corresponding FLIDs, for the nanocrystal shown in Fig. 2 at three different potentials. Binary blinking seen at V = 0 V is largely suppressed at V = +0.6 V, whereas electron injection is achieved at V = −0.6 V. In the FLID colour scale, red corresponds to the most frequently occurring lifetime–intensity pair, and probabilities less than 1% of this maximum are indicated by dark blue. A linear scaling from blue to red is used between these extremes. b, Data from the same nanocrystal, acquired on a different day, display continuous photoluminescence intensity and lifetime fluctuations, typical of flickering. At V = −1.1 V, we observe emission from a doubly charged exciton, X²⁻. All data were analysed with a bin size of 50 ms. Full time trajectories for a and b are shown in Supplementary Fig. 1.

a, Photoluminescence intensities (black lines) and average lifetimes (red lines), and corresponding FLIDs, for a nanocrystal showing the B-type OFF state; analysis done with a 10-ms bin. Full time trajectories are shown in Supplementary Fig. 6. b, The model of B-type blinking. The B-type OFF state is due to the activation of recombination centres (R) that capture hot electrons at a rate, γ_D, that is higher than the intraband relaxation rate, γ_B (the ground and the excited electron states are shown as 1S_e and 1P_e, respectively; 1S_h is the band-edge hole state). The position of the Fermi level, E_F, relative to the trap energy, E_R, is determined by the electrochemical potential and controls the occupancy of the surface trap R. This, in turn, allows for electrochemical control of B-type blinking.

a, FLIDs indicating a nanocrystal switching from B-type blinking at −0.8 V (left) to A-type blinking at −1 V (right). Details of the analysis are given in Supplementary Fig. 9. b, Statistics for ON (red circles) and OFF (black squares) times for the FLIDs in a, in the log–log representation. At −0.8 V (B-type blinking), the data can be fitted to a power-law distribution, ∝t^−α, with α = 1.17 for the ON times (red line) and α = 1.00 for the OFF times (black line). At −1 V (A-type blinking), this description is no longer valid; however, the data can be closely fitted by introducing an exponential cut-off such that the distribution is ∝t^−αexp(−t/t_c), where α = 0.54 and t_c = 73.4 ms for the ON times (red line) and α = 0.37 and t_c = 70.8 ms for the OFF times (black line).