CdSe nanocrystal sensitized photon upconverting film.

Here, films using CdSe nanocrystal (NC) triplet photosensitizers in conjunction with diphenylanthracene (DPA) emitters were assembled to address several challenges to practical applications for solution-based photon upconversion. By using poly(9-vinylcarbazole) as a phosphorescent host in this film, volatile organic solvents are eliminated, the spontaneous crystallization of the emitter is significantly retarded, and ∼1.5% photon upconversion quantum yield (out of a maximum of 50%) is obtained.

On the size-dependence of CdSe nanocrystals for photon upconversion with anthracene.

In triplet-triplet annihilation based photon upconversion, controlling triplet energy transfer (TET) through the system is key to unlocking higher efficiencies. In this work, we vary the size of colloidally synthesized CdSe nanocrystals (NCs) to examine the effects on TET during photon upconversion, using steady-state measurements and transient absorption spectroscopy. As the CdSe NC size increases, the photon upconversion quantum yield (QY) decreases due to the decrease in the rate of TET from CdSe to the surface bound anthracene transmitter ligand, as expected for the Marcus description of energy transfer from the transmitter to the NC.

Primary amines enhance triplet energy transfer from both the band edge and trap state from CdSe nanocrystals.

In this study, the role that primary amines play during triplet energy transfer from photoexcited CdSe nanocrystals (NCs) was examined. Colloidally synthesized CdSe NCs were placed in varying concentrations of 1-propyl- or 1-octylamine, with and without 2-anthracenecarboxylic acid transmitter ligands attached. This primary amine increases upconversion quantum yield approximately 5-fold.