Abstract:
Triplet-triplet annihilation upconversion (TTA-UC) is a process which converts two low energy photons into one higher-energy excited state. TTA-UC has recently received attention for its potential application to many light driven processes, such as improving efficiency in photovoltaic devices and allowing use of low energy light sources for in vivo applications, including bioimaging, optogenetics, and photochemotherapy. Each of these applications has a different set of energetic requirements, which has created a need for a diverse library of upconverting materials. Additionally, these applications benefit from improved upconversion efficiency in solid-state, a task that has proven challenging for the traditionally solution-phase process. Macromolecular scaffolds are a promising avenue to tune the electronic communication between chromophores and control intermolecular packing in solid-state organization. In this presentation, I will be reporting the investigation of dendrimers with annihilator-functionalized termini and linear annihilator polymers as methods to control local annihilator concentration and communication. Multi-annihilator dendrimers exhibit higher upconversion yields at low concentrations compared to monomer analogs; however, decreased upconversion yields are observed in the largest dendrimer generations due to parasitic excimer formation. Linear annihilator co-polymer scaffolds with alternating anthracene and benzene or naphthalene bridges had predictable ground state optical properties based on bridge connectivity, interchromophore distance, and planarity. Naphthalene-containing, non-conjugated polymers were found to be the most efficient at intramolecular TTA-UC.
