Triplet fusion upconversion using sterically protected 9,10-diphenylanthracene as the emitter

Area of Science:

• Materials Science
• Photochemistry
• Organic Electronics

Background:

• Triplet fusion upconversion (TF-UC) is a promising photophysical process for converting lower-energy photons to higher-energy ones.
• Solid-state TF-UC is hindered by chromophore aggregation and phase separation, limiting efficiency.
• Developing stable and efficient solid-state TF-UC materials is crucial for applications like organic photovoltaics and lighting.

Purpose of the Study:

• To investigate the impact of bulky substituents on 9,10-diphenylanthracene (DPA) derivatives on TF-UC performance in various media.
• To explore the role of emitter-sensitizer dispersion in solid-state TF-UC efficiency.
• To assess the photostability of modified DPA emitters under UV irradiation and oxygen exposure.

Main Methods:

• Synthesis of two bulky DPA derivatives (bDPA-1 and bDPA-2) with isopropyl groups.
• Fabrication of TF-UC systems using bDPA derivatives as emitters and platinum octaethylporphyrin (PtOEP) as sensitizer in toluene solution, polyurethane films, and polyvinyl alcohol matrices.
• Comprehensive investigation of TF-UC performance, including quantum yield (ΦUC) and excitation intensity threshold, in different matrices.
• Evaluation of photostability under UV irradiation in the presence of oxygen.

Main Results:

• Bulky DPAs showed minimal efficiency difference compared to DPA in solution and thin films.
• Significant enhancement in TF-UC quantum yield (ΦUC = (0.92 ± 0.05)%) and a lower excitation threshold (52 mW cm-2) were achieved in bDPA-2/PtOEP nano/micro-crystals.
• Improved dispersibility of PtOEP sensitizer within bDPA-2 emitter crystals was identified as the key factor for enhanced TF-UC performance.
• Bulky DPAs exhibited superior photostability under UV irradiation and oxygen exposure compared to the unmodified DPA.

Conclusions:

• Incorporating bulky substituents into DPA emitters is an effective strategy to improve solid-state TF-UC efficiency by enhancing chromophore dispersion.
• Nano/micro-crystalline systems offer a viable platform for achieving high TF-UC performance and stability.
• The developed bDPA derivatives and nano/micro-crystal approach provide a pathway for designing advanced solid-state TF-UC materials for various optoelectronic applications.