We report four supermolecular chromophores based on (porphinato)zinc(II) (PZn) and (polypyridyl)metal units bridged via ethyne connectivity (Pyr(1)RuPZn(2), Pyr(1)RuPZnRuPyr(1), Pyr(1)RuPZn(2)RuPyr(1), and OsPZn2Os) that fulfill critical sensitizer requirements for NIR-to-vis triplet-triplet annihilation upconversion (TTA-UC) photochemistry. These NIR sensitizers feature: (i) broad, high oscillator strength NIR absorptivity (700 nm < lambda(max(NIR)) < 770 nm; 6 x 10(4) M-1 cm(-1) < extinction coefficient (lambda(max(NIR))) < 1.6 x 10(5) M-1 cm(-1)); 820 cm(-1) < fwhm < 1700 cm(-1)); (ii) substantial intersystem crossing quantum yields; (iii) long, microsecond time scale T-1 state lifetimes; and (iv) triplet states that are energetically poised for exergonic energy transfer to the molecular annihilator (rubrene). Using low-power noncoherent illumination at power densities (1-10 mW cm(-2)) similar to that of terrestrial solar photon illumination conditions, we demonstrate that Pyr(1)RuPZn(2), Pyr(1)RuPZn(2)RuPyr(1), and Pyr(1)RuPZnRuPyr(1) sensitizers can be used in combination with the rubrene acceptor/annihilator to achieve TTA-UC: these studies represent the first examples whereby a low-power noncoherent NIR light source drives NIR-to-visible upconverted fluorescence centered in a spectral window within the bandgap of amorphous silicon.