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.
Nanoparticle-based photothermal heating degrades polymer from the inside-out, creating pockets of depolymerized material around each nanoscale heating site.
Atomic layer deposition (ALD) is a key technique in processing new materials compatible with complex architectures. While the processing space for Li-containing ALD thin films has been relatively well explored recently, the space for other alkali metal thin films (e.g., Na) is more limited. Thermal ALD and plasma-enhanced ALD (PEALD) lithium phosphorus oxynitride [Kozen et al., Chem. Mater. 27, 5324 (2015); Pearse et al., Chem. Mater. 29, 3740 (2017)] processes as well as analogous thermal sodium phosphorus oxynitride (NaPON) (Ref. 13) have been previously developed as conformal ALD solid state electrolytes. The main difference between the Na and Li processes is the alkali tert-butoxide precursor (AOtBu, A = Li, Na). One would expect such an isoelectronic substitution with precursors that have similar structure and properties to correlate with a similarly behaved ALD process. However, this work demonstrates that the PEALD NaPON process unexpectedly behaves quite differently from its Li counterpart, introducing some insight into the development of Na-containing thin films. In this work, we demonstrate process development and characterization of an analogous low temperature (250 °C) PEALD of NaPON. This process demonstrates significant tunability of N coordination states by varying plasma nitrogen exposure time. Electrochemical characterization showed an ionic conductivity of 8.2 × 10−9 S/cm at 80 °C and activation energy of 1.03 eV. This first instance of low temperature NaPON deposition by PEALD shows promise for further development and understanding of more versatile processing of Na thin film materials.
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