Sensitized triplet-triplet-annihilation-based photon upconversion (TTA-UC) permits the conversion of light into radiation of higher energy and involves a sequence of photophysical processes between two dyes. In contrast to other upconversion schemes, TTA-UC allows the frequency shifting of low-intensity light, which makes it particularly suitable for solar-energy harvesting technologies. High upconversion yields can be observed for low viscosity solutions of dyes; but, in solid materials, which are better suited for integration in devices, the process is usually less efficient. Here, it is shown that this problem can be solved by using transparent nanodroplet-containing polymers that consist of a continuous polymer matrix and a dispersed liquid phase containing the upconverting dyes. These materials can be accessed by a simple one-step procedure that involves the free-radical polymerization of a microemulsion of hydrophilic monomers, a lipophilic solvent, the upconverting dyes, and a surfactant. Several glassy and rubbery materials are explored and a range of dyes that enable TTA-UC in different spectral regions are utilized. The materials display upconversion efficiencies of up to ≈15%, approaching the performance of optimized oxygen-free reference solutions. The data suggest that the matrix not only serves as mechanically coherent carrier for the upconverting liquid phase, but also provides good protection from atmospheric oxygen.

Photon upconversion based on sensitized triplet–triplet annihilation (sTTA‐UC) is a wavelength‐shifting technique with potential use in actuators, sensing, and solar technologies. In sTTA‐UC, the upconverted photons are the result of radiative recombination of high‐energy singlets, which are created through the fusion of metastable triplets of two annihilator/emitter molecules. The emitter triplets are populated via energy transfer (ET) from a low‐energy absorbing light‐harvester/sensitizer. The process is highly efficient at low powers in solution but becomes relatively ineffective in solid matrices since the limited molecular mobility precludes bimolecular interactions. The realization of efficient solid‐state upconverters that exhibit long‐term stability and are compatible with industrial fabrication processes is an open challenge. Here, nanophase‐separated polymer systems synthesized under ambient conditions that contain the upconverting dyes in liquid nanodomains is reported. The nanostructured polymers show an excellent optical quality, an outstanding upconversion efficiency of up to ≈23%, and excellent stability in air, with only negligible performance losses over a period of three months. Moreover, the dyes’ confinement in nanosized domains <50 nm results in an increased effective local density of chromophores that enables hopping‐assisted ET and TTA and confers to the upconversion process peculiar kinetics that enhances the material performance at low powers.

Thienoacenes and furoacenes are among the most frequent molecular units found in organic materials. The efficient synthesis of morphologically different heteroacenes and the rapid determination of their solid-statea nd electronic properties are still challenging tasks, which slow down progress in the development of new materials. Here, we report af lexible and efficient synthesis of unprecedented heterotetracenes based on ap latinum-and gold-catalyzed cyclization-alkynylation domino process using EthynylBenziodoXole (EBX) hypervalent iodine reagents in the key step. The proof-of-principlei ns ilico estimation of the synthesized tetracenes'c harget ransport properties reveals their strong dependence on both the positionand nature of the heteroatoms in the ring system.Abroad range of mobility is predicted, with some compounds displaying performance potentiallyc omparable to that of state-of-the-art electronic organic materials.