Colloidal PbS quantum dot sensitized NIR-to-visible photon upconversion via triplet-triplet annihilation

摘要

Photon upconversion (UC) has recently been received growing attention due to potential application in various fields such as photocatalysis, photovoltaic and bio-imaging.1,2 More specifically, an upconversion system which absorbs NIR wavelengths (> 750 nm, 1.65 eV) is rather meaningful to utilize 46% of untended solar flux in this region. Triplet-triplet annihilation (TTA)-UC with inorganic quantum dot (QD) as sensitizer has recently shown an attractive possibility to utilize the NIR photons. The band gap tunability of QD of the narrow gap semiconductors such as PbS and PbSe makes it prime candidate for NIR sensitizer of TTA-UC by combining with the polyaromatic hydrocarbons that have low-lying triplet energy level (such as rubrene, ET=1.14 eV) as annihilator. Actually, as for TTA-UC system with NIR-QD, PbSe-rubrene3 and PbS-(TES-ADT)4 in dispersion solution and PbS-rubrene in solid film form5,6 have been investigated so far and the UC quantum yields (QY’s) were reported. However, report on the dispersion solution of PbS-rubrene is seldom and limited for the relative comparison of UC-QY.