All Organic Nanofibers As Ultralight Versatile Support for Triplet–Triplet Annihilation Upconversion

Abstract

We present a method for the fabrication of ultralight upconverting mats consisting of rigid polymer nanofibers. The mats are prepared by simultaneously electrospinning an aqueous solution of a polymer with pronounced oxygen-barrier properties and functional nanocapsules containing a sensitizer/emitter couple optimized for triplet–triplet annihilation photon upconversion. The optical functionality of the nanocapsules is preserved during the electrospinning process. The nanofibers demonstrate efficient upconversion fluorescence centered at λmax = 550 nm under low intensity excitation with a continuous wave laser (λ = 635 nm, power = 5 mW). The pronounced oxygen-barrier property of the polymer matrix may efficiently prevent the oxygen penetration so upconversion fluorescence is registered in ambient atmosphere. The demonstrated method can be used for the production of upconverting ultralight porous coatings for sensors or upconverting membranes with freely variable thickness for solar cells.

Photochemical upconversion: present status and prospects for its application to solar energy conversion

“…150 Self-organized micellar carriers based on non-ionic surfactants have been presented and likewise allow transference of the system into water. 151 There are also several alternatives to the highly volatile solvents: Ionic liquids have been presented as a completely nonvolatile host matrix, 123 while hexadecane/polyisobutylene was found to be a less volatile host, also providing some degree of oxygen protection.…”

Transition-Metal Complexes for Triplet–Triplet Annihilation-Based Energy Upconversion

“…Recently, TTA-based upconversion with the sensitizer (Pd-3)/acceptor (A-12) couple was reported [37]. And a new Pd(II) complex (Pd-9) was synthesized and can be used as the sensitizer [38].…”

Improving triplet-triplet-annihilation based upconversion systems by tuning their topological structure

“…In experimental situations, the triplet hopping rate J depends on the distance and the orientation between the molecules. Furthermore, a very high viscosity of the host material is detrimental for the upconversion process, 10,11,15,17 i.e., rubbery host materials work better than stiff hosts, since the flexibility most likely increases the triplet diffusion length. Hence, performing simulations with an averaged, constant hopping rate should result in reasonable estimates for rubbery low viscosity materials, where sensitizers and emitters have some freedom to move.…”

“…While reasonably efficient upconverters exist now in solids, [10][11][12][13][14][15][16][17][18] their efficiency stays below that of solution based upconverters. 9,[19][20][21][22][23][24][25][26][27] Hence, the main challenge in this field is the design of solid upconverters with comparable, or even better efficiency than solution based materials.…”