Fluoropolymer-diluted small molecule organic semiconductors with extreme thermal stability

Abstract

Thermal stability is important for many thin film organic semiconductor devices but is challenging due to their weakly Van der Waals-bonded nature. Here, we show that diluting common small molecule hole transport materials through co-evaporation with the amorphous fluoropolymer Teflon AF leads to a dramatic improvement in their thermal and morphological stability without sacrificing electrical performance. Blend films with 25 vol. % Teflon decrease the drive voltage of single layer hole-only devices by more than 30% and dramatically increase their operating temperature limit to over 250 °C. The stability improvement appears to result from a nanoscale network of Teflon chains that repolymerize throughout the blend film following evaporation and inhibit gross movement of the organic semiconductor molecules. These results open up a pathway to stabilize the morphology of small molecule organic semiconductors and point to a more general opportunity to exploit semiconductor dilution to systematically vary thermal, optical, and other material properties without compromising electrical transport.

Nanoprojectile Secondary Ion Mass Spectrometry for Nanometrology of Nanoparticles and Their Interfaces

“…We have previously applied NP-SIMS to characterize other types of nanoassemblies, e.g., characterizing the directed self-assembly of macromolecules and organic semiconductors. 43,44 Such analysis could be refined using the data analysis methods described above of grouping like nanovolumes and may allow for defects in these types of assemblies to be tracked and molecularly characterized.…”

“…The results show that despite the relatively large sampling volume of nanoprojectile impacts (10–15 nm in diameter) we can differentiate measurements on 3–5 nm nanoparticles based on the impact parameter, allowing for measurements which occur on the particle core to be differentiated from those occurring near the particle edge based on the detected SIs and demonstrating that molecular analysis can be undertaken at a scale below 5 nm. We have previously applied NP-SIMS to characterize other types of nanoassemblies, e.g., characterizing the directed self-assembly of macromolecules and organic semiconductors. , Such analysis could be refined using the data analysis methods described above of grouping like nanovolumes and may allow for defects in these types of assemblies to be tracked and molecularly characterized.…”

Nanoprojectile Secondary Ion Mass Spectrometry for Analysis of Extracellular Vesicles

“…The data from the collection of impacts will contain information of like-sites. They can be grouped for the accurate identification of analytes and evaluating correlations among co-emitted species. , Over the past decade, we employed NP-SIMS to answer many nanoscale questions; evaluating the vertical alignment of macromolecular bottle brush polymers produced by self-assembly, measuring the molecular homogeneity of organic semiconductors used for extreme thermal applications, investigating the chemical environment around nanoparticles, and evaluating ligand loading on nanoparticles . Given the fact that NP-SIMS probes the surface with a sub-EV resolution (20 nm probe area vs 30 to 200 nm single EV dimensions) and generates detectable SI ejecta from each impact, we hypothesized that our technique may be used for chemical analysis of EVs with single particle resolution.…”

Active refractive index control using a stably evaporable perfluororesin for high-outcoupling-efficiency organic light-emitting diodes

“…By co-depositing the perfluororesin and a hole transport material with a volume ratio of 50 : 50, the refractive index of the layer can be effectively lowered to 1.56 at 550 nm while keeping a smooth surface and without deteriorating the electrical properties. Although the use of a perfluororesin was proposed in a previous study, 21 the material easily decomposed in the vacuum deposition process, 22 which led to unforeseen chemical reactions, and the outcoupling efficiency of the corresponding OLED was not improved. In contrast, the perfluororesin used in the present study can be stably evaporated without chemical decomposition.…”