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.

Nanoscale molecular characterization plays a crucial role in enhancing our insights into fundamental and materials processes occurring at the nanoscale. However, for many traditional techniques, measurements on different ensembles are mixed and the analytical result reflects the average surface composition or arrangement. Advances in nanometrologies that allow for measurements to be differentiated based on the chemical environment examined are critical for accurate analysis. Here, we present a variant of secondary ion mass spectrometry, SIMS, termed nanoprojectile SIMS, NP-SIMS, capable of nanoscale molecular analysis. The technique examines the sample with a suite, 106–107, of individual gold nanoprojectiles (e.g., Au400 4+) which stochastically probe the surface. Analysis of coemitted ions from each impact allows for the inspection of colocalized moieties within the ejected volume of a single projectile impact (10–15 nm in diameter). If some of these 106–107 measurements arise from nanodomains of similar composition, data can be grouped based on the detected secondary ions. We applied the method to examine a mixture of three different-sized nanoparticles with identical metal cores (3–5 nm in diameter), differing in the length of the attached ligand (decanetiol, tetradecanethiol, and hexadecanethiol). Using NP-SIMS, we determined the relative abundance of the three particles on the surface and isolated measurements based on the impact parameter between the impacting nanoprojectile and the surface particle, demonstrating that measurements occurring near the center of the particle can be differentiated from those at the particle–particle and particle–substrate interfaces. The results suggest that the described methodology is well-suited for molecular analysis of nanoassemblies and may be applied for tracking defects. Here we demonstrate that, using NP-SIMS, ensemble averaging can be avoided and molecular analysis can be undertaken at a scale below 5 nm, allowing for nanoscale molecular analysis of nano-objects and their interfaces.