CdSe nanocrystal sensitized photon upconverting film

Area of Science:

• Materials Science
• Nanotechnology
• Photochemistry

Background:

• Photon upconversion (PUC) is crucial for applications like solar energy and bioimaging.
• Solution-based PUC systems face challenges including solvent volatility and emitter crystallization.
• Developing stable, efficient solid-state PUC systems is highly desirable.

Purpose of the Study:

• To create stable, solid-state photon upconversion films.
• To investigate the efficiency limitations of PUC in solid matrices.
• To enhance the practical applicability of photon upconversion.

Main Methods:

• Assembly of films using cadmium selenide (CdSe) nanocrystal (NC) triplet photosensitizers and diphenylanthracene (DPA) emitters.
• Utilizing poly(9-vinylcarbazole) as a phosphorescent host material.
• Employing transient absorption spectroscopy for time-resolved measurements.

Main Results:

• Achieved a photon upconversion quantum yield of approximately 1.5%.
• Demonstrated significantly retarded spontaneous crystallization of the emitter.
• Observed an exceptionally long triplet lifetime of 3.4 ± 0.3 ms.
• Identified incomplete triplet-triplet annihilation as the primary efficiency limitation.

Conclusions:

• Solid-state films using CdSe NCs and DPA emitters offer a promising alternative to solution-based systems.
• Poly(9-vinylcarbazole) host effectively suppresses solvent use and emitter crystallization.
• Long triplet lifetimes contribute to PUC efficiency, but triplet-triplet annihilation rates limit overall performance.