Organic Polymer Hosts for Triplet–Triplet Annihilation Upconversion Systems

Abstract

Triplet–triplet annihilation upconversion (TTA-UC) is a process by which a lower energy photon can be upconverted to a higher energy state. The incorporation of TTA-UC materials into solid-state hosts has enabled advances in solar energy and many other applications. The choice of host system is, however, far from trivial and often calls for a careful compromise between characteristics such as high molecular mobility, low oxygen diffusion, and high material stability, factors that often contradict one another. Here, we evaluate these challenges in the context of the state-of-the-art of primarily polymer hosts and the advantages they hold in terms of material selection and tunability of their diffusion or mechanical or thermal properties. We encourage more collaborative research between polymer scientists and photophysicists in order to further optimize the current systems and outline our thoughts for the future direction of the field.

Challenges, progress and prospects in solid state triplet fusion upconversion

“…TET and TTA in the liquid phase and in some polymer matrices (those that allow migration of molecules) is mediated by molecular diffusion. 68,69 Excited annihilators with triplet character diffuse through the matrices and annihilate before the triplet lifetime elapses. However, if the sensitizers and annihilators are immobile, as in the solid state, triplet energy diffusion then depends on the mobility of excitons through molecular sites rather than molecular diffusion (Fig.…”

Versatile, stable, and air-tolerant triplet–triplet annihilation upconversion block copolymer micelles

“…Considering the high T g value of the PDPAMA block, the mobility of donors and acceptors inside the micellar core was significantly limited, and thus the TTA process occured more likely through the triplet energy migration (TEM) mechanism. 45 The quantum efficiency of TTA-UC is an important characteristic and depends on many factors according to the mechanism of TTA-UC. 23 For example, the molar ratio of the triplet donor to the acceptor is crucial for the luminous intensity of TTA-UC.…”

Recent Advances in the Photoreactions Triggered by Porphyrin-Based Triplet–Triplet Annihilation Upconversion Systems: Molecular Innovations and Nanoarchitectonics

“…As a new upconversion technology, TTA-UC developed rapidly in recent years. Many related issues have been widely investigated, such as how to improve upconversion efficiency [ 50 , 51 ], how to overcome oxygen quenching [ 52 , 53 ], and how to achieve solid-state applications [ 54 , 55 , 56 , 57 , 58 ]. Furthermore, a great many TTA-UC-based examples for practical applications have also emerged, including solar cells [ 59 , 60 ], bioimaging [ 61 , 62 ], circularly polarized luminescence [ 63 , 64 , 65 ], sensing [ 66 , 67 ], and photoreactions [ 31 ].…”