Sensitized Low-Power Photon Upconversion in Molecular Glasses

New molecular organic glasses capable of performing low-power photon upconversion and investigation of the factors governing efficiency and nature of the emitted light.

Low-power photon upconversion (UC) via triplet-triplet annihilation (TTA) is a nonlinear process converting incident radiation into higher energy light using relatively low power densities (< 100 mW cm-2). TTA-UC systems usually consist of a two organic dyes: a sensitizer, harvesting incoming light and an emitter. In the last years, several solid-state polymer and non-polymer-based UC materials and material concepts have been reported making it important to understand the factors governing solid-state TTA-UC. Also, TTA-UC materials have been reported to be suitable for applications ranging from biological microscopy to photochemical water splitting.
Emitter-based molecular glasses (MGs) represent a new strategy for solid-state upconverting materials. Our research efforts aim to investigate the effects of morphology, sensitizer type and concentration on UC. Green to blue upconverting 9,10-diphenylanthracene emitter glasses doped with palladium- or platinum porphyrin-based sensitizers (Pd or PtOEP) were found to exhibit a stronger UC compared to their crystalline counterparts. Porphyrin aggregation was directly observed spectroscopically for PtOEP-doped crystalline samples resulting in a decrease of UC efficiency. UC-MG constitute a unique model systems for the study of the  photophysical implications of molecular disorder, chromophore aggregation and morphology on TTA-UC.

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254