Consolidation and performance gains in plasma-sintered printed nanoelectrodes

• Published in: Nanoscale advances 2023-08, Vol.5 (16), p.4124-4132
• Main Authors: Engel, Lukas F, González-García, Lola, Kraus, Tobias
• Format: Article
• Language: English
• Subjects: Chemistry
• ISSN: 2516-0230; 2516-0230
• DOI: 10.1039/d3na00293d

We report on the unusual, advantageous ageing of flexible transparent electrodes (FTEs) that were self-assembled from oleylamine-capped gold nanospheres (AuNPs) by direct nanoimprinting of inks with different particle concentrations ( c Au = 3 mg mL −1 to 30 mg mL −1 ). The resulting lines were less than 2.5 μm wide and consisted of disordered particle assemblies. Small-Angle X-ray Scattering confirmed that particle packing did not change with ink concentration. Plasma sintering converted the printed structures into lines with a thin, electrically conductive metal shell and a less conductive hybrid core. We studied the opto-electronic performance directly after plasma sintering and after fourteen days of storage at 22 °C and 55% rH in the dark. The mean optical transmittance T&cmb.macr; 400-800 in the range from 400 nm to 800 nm increased by up to 3%, while the sheet resistance R sh strongly decreased by up to 82% at all concentrations. We correlated the changes with morphological changes visible in scanning and transmission electron microscopy and identified two sequential ageing stages: (I) post-plasma relaxation effects in and consolidation of the shell, and (II) particle re-organization, de-mixing, coarsening, and densification of the core with plating of Au from the core onto the shell, followed by solid-state de-wetting (ink concentrations c Au < 15 mg mL −1 ) or stability ( c Au ≥ 15 mg mL −1 ). The plating of Au from the hybrid core improved the FTEs' Figure of Merit FOM = T&cmb.macr; 400-800 · R sh −1 by up to 5.8 times and explains the stable value of 3.3%· Ω sq −1 reached after 7 days of ageing at c Au = 30 mg mL −1 . Oleylamine-capped Au nanoparticles were imprinted and plasma-sintered, forming flexible transparent electrodes with a closed Au shell and hybrid core. They consolidate with time, increasing the electrode figure of merit up to 5.8 times, decreasing sheet resistance.