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 similar to 1.5% photon upconversion quantum yield (out of a maximum of 50%) is obtained. Transient absorption spectroscopy on nanosecond-to-microsecond time scales reveals this efficiency is enabled by an exceptionally long triplet lifetime of 3.4 +/- 0.3 ms. Ultimately, we find the upconversion efficiency is limited by incomplete triplet-triplet annihilation, which occurs with a rate 3-4 orders of magnitude slower than in solution-phase upconversion systems.

Automated summary

Films using CdSe nanocrystal triplet photosensitizers with DPA emitters were assembled to address challenges in solution-based photon upconversion applications. The use of poly(9-vinylcarbazole) as a phosphorescent host eliminated volatile organic solvents and achieved a 1.5% photon upconversion quantum yield. The efficiency was limited by incomplete triplet-triplet annihilation due to a slower rate compared to solution-phase systems.