Large Enhancement of Photoluminescence Obtained in Thin Polyfluorene Films of Optimized Microstructure.

There is a clearly demonstrated relationship between the microstructure, processing and resulting optoelectronic properties of conjugated polymers. Here, we exploited this relationship by exposing polyfluorene thin films to various solvent vapors via confined-solvent vapor annealing to optimize their microstructure, with the final goal being to enhance their emission properties. Our results have demonstrated enlargements in photoluminescence intensity of up to 270%, 258% and 240% when thin films of polyfluorenes of average molecular weights of 105,491 g/mol, 63,114 g/mol and 14,000 g/mol, respectively, experienced increases in their -phase fractions upon processing.

Processing of Thin Films Based on Cellulose Nanocrystals and Biodegradable Polymers by Space-Confined Solvent Vapor Annealing and Morphological Characteristics.

L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate--hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers with cellulose nanocrystal fillers and further processing the resulting materials via space-confined solvent vapor annealing. Cellulose was previously obtained from renewable biomass and further converted to cellulose nanocrystals by hydrolysis with the lactic acid.

Self-Assembly of Block Copolymers in Thin Films Swollen-Rich in Solvent Vapors.

In this study we have employed a polymer processing method based on solvent vapor annealing in order to condense relatively large amounts of solvent vapors onto thin films of block copolymers and thus to promote their self-assembly into ordered nanostructures. As revealed by the atomic force microscopy, a periodic lamellar morphology of poly(2-vinylpyridine)--polybutadiene and an ordered morphology comprised of hexagonally-packed structures made of poly(2-vinylpyridine)--poly(cyclohexyl methacrylate) were both successfully generated on solid substrates for the first time.

Growth of Hybrid Perovskite Crystals from CHNHPbICl Solutions Subjected to Constant Solvent Evaporation Rates.

In this work, we subjected hybrid lead-mixed halide perovskite (CHNHPbICl) precursor inks to different solvent evaporation rates in order to facilitate the nucleation and growth of perovskite crystals. By controlling the temperature of perovskite solutions placed within open-air rings in precise volumes, we established control over the rate of solvent evaporation and, thus, over both the growth rate and the shape of perovskite crystals. Direct utilization of diluted lead-mixed halide perovskites solutions allowed us to control the nucleation and to favor the growth of only a low number of perovskite crystals.

Enhancing Photoluminescence Quenching in Donor-Acceptor PCE11:PPCBMB Films through the Optimization of Film Microstructure.

We show that a precise control of deposition speed during the fabrication of polyfullerenes and donor polymer films by convective self-assembly leads to an optimized film microstructure comprised of interconnected crystalline polymer domains comparable to molecular dimensions intercalated with similar polyfullerene domains. Moreover, in blended films, we have found a correlation between deposition speed, the resulting microstructure, and photoluminescence quenching. The latter appeared more intense for lower deposition speeds due to a more favorable structuring at the nanoscale of the two donor and acceptor systems in the resulting blend films.