Properties of the PbS/Ligand systems studied herein.

Ligand	λ #Ligand/QDa	τ TET b (ns)	k 0 c (s−1)	τ Ligend d(μs)	Relative UC Intensitye	ϕ TET−A f (%)
Tc-CA	16.6	73.3 ± 3.6	9.7 ± 0.4 × 105	60.1 ± 1.5	0.26	98.0
Tc-AA	10.2	114 ± 10	6.8 ± 0.5 × 105	29.5 ± 1.6	0.05	95.7
Tc-SH	24.6	116 ± 9	3.3 ± 0.3 × 105	2.9 ± 0.1	0.02	76.2
BAT	40.7	567 ± 102	3.7 ± 0.5 × 104	148 ± 25	1	99.3

^aAverage number of ligands attached per QD, determined from UV-vis absorption measurements.

^bTime constant for the rise of the triplet signal from single-exponential fits to ns-TA data.

^cIntrinsic rate constant for triplet transfer to one ligand obtained assuming a Poisson distribution of bound ligands.

^dLifetime of the ligand triplet state, from fits to ns-TA data.

^eRelative upconversion intensity for PbS/ligand sensitizers with 10 mM rubrene upon 785 nm excitation.

^fEstimated triplet transfer efficiency for triplet transfer from ligands to rubrene in toluene, assuming k_TET = 1 × 10⁸ M⁻¹ s⁻¹.