Understanding and controlling the emission efficiency and recombination dynamics of bi-excitonic states (i.e. Q<sub>BX</sub> and τ<sub>BX</sub>) in semiconductor nanocrystal quantum dots (NQDs) holds the key to many novel technological applications including optical amplification, entangled photon-pair generation and carrier multiplication. Here we present novel single particle spectroscopy approaches capable of measuring these parameter directly. Our approaches are based on second order photon correlation spectroscopy (<i>g</i><sup>(2)</sup> (τ)) and can also be applied to small clusters of NQDs to determine the number of NQDs in a cluster together with average value of Q<sub>BX</sub> and τ<sub>BX</sub>. Specifically, first we demonstrate that the ratio of the areas of center and side peaks of the <i>g</i><sup>(2)</sup> (τ) function of the spectrally integrated PL of a single NQD provide a precise measure of the ratio of the quantum yield of single and bi-exciton states. Next, we present a time gated photon correlation spectroscopy approach that allows separation of the effects of multi-exciton emission and NQD clustering in g(2) measurements. Finally, we present how the emission of bi-excitons can be separated in <i>g</i><sup>(2)</sup> (τ) measurements and extract decay dynamics of bi-excitons without any ambiguity.