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Proton conduction in the current polymer electrolyte membrane depends on water molecules, which necessitates high-humidity environments. On the contrary, proton conduction in low-humidity environments has been required for expanding operation conditions of polymer electrolyte fuel cells. Recently, ionic liquids (ILs) have been focused on novel proton conductive materials, however, the ILs were hard to fabricate the self-standing membrane owing to their fluidity. In this paper, we have developed composite materials composed of ILs and inorganic nanoparticles by coating ILs as polymer states (PILs) on the surface of nanoparticles. Notably, this material has obtained a powder form, and we have succeeded in suppressing the fluidity of ILs. The PILs-coated nanoparticles have achieved good proton conductivity over 10−2 S cm−1 at 95% RH, also indicated over 10−4 S cm−1 under 60% RH. In addition, we have clarified the relationship between the thickness of PILs and proton conductivities.

Polymer electrolyte membrane (PEM) fuel cells have challenges in operation under low-humidity conditions caused by a proton conduction mechanism dependent on water. We focused on polymeric ionic liquids (PILs), which are promising for high proton conductivity under a wide range of environments because they have the characteristics of polymer electrolyte liquids. However, it is difficult to fabricate self-standing membranes of PILs due to their high hygroscopicity and fluidity. In this paper, to inhibit the fluidity of the PIL in developing a self-standing PEM, the hydrophobic chain segment of styrene is inserted between the PILs of poly(vinylphosphonic acid/1-propylimidazole) (P(VPA/1PIm)) by RAFT polymerization. The synthesized sample of P(VPA/1PIm)-block-polystyrene is potentially applicable to PEM materials because it was obtained in powder state, having a high heat resistance of up to 300 °C, and exhibiting a proton-conducting property under a wide range of environments.

Organic–inorganic hybrid lead halide perovskite nanocrystals (PeNCs) have received great attention as a light source for perovskite LEDs (PeLEDs) owing to the superior optical properties. However, PeNCs typically use octylamine (OAm) as capping ligands which have insulating properties. Exploring a desirable short alkylamine instead of OAm is required for the improvement of PeLEDs. Here, as one of the strategies to solve this issue, the effects of alkylamine chain length for optical properties of PeNCs and PeLED characteristics are investigated. Pentylamine is an optimal short alkylamine and precipitate luminescent PeNCs with high PLQY values of 90%. Importantly, pentylamine maintains a relatively high PLQY of 48% after spin-coating, due to the durability pentylamine has to ethyl acetate as a washing solvent. PeNCs capped with pentylamine also demonstrate an external quantum efficiency of over 1% with luminance of over 2000 cd cm−2, indicating that pentylamine has the potential to overcome the insulator properties of PeNC thin film.