Additional file 1 of Ink-lithographic fabrication of silver-nanocrystal-based multiaxial strain gauge sensors through the coffee-ring effect for voice recognition applications

Additional file 1: Figure S1. HRTEM images of a as-synthesized (left) and NH4Br-treated (right) Ag NCs. b UV–vis absorbance spectra, c FT-IR absorption profiles, and d XRD patterns of the as-synthesized (black) and NH4Br-treated Ag NCs with continuously (blue) and alternately printed patterns (red). Figure S2. Profile of waveform employed for inkjet printing the ligand ink. Figure S3. Plot of the AFM data corresponding to the Fig. 1c results. Figure S4. Optical image for investigating contact angle of the ligand ink on the Ag NC thin films. Figure S5. Optical images of ligand-ink-treated Ag NC line patterns. a Continuously (left) and alternately printed (right) Ag NC line patterns. b Changes in line width of the Ag NC line patterns with different micro-spacings of the jetting droplets (scale bar = 50 μm). Figure S6. a Front- and b top view optical images of the multiaxial strain gauge sensors attached to the 0.6%-strain-curved structure. Figure S7. a Schematic of films with alternately printed Ag NC patterns subjected to bending at different rotations. b Detailed schematic of alternately printed Ag NC patterns. Detailed top-view schematics of changes in the c alternately and d continuously printed Ag NC patterns with bending. Figure S8. a Gauge factor of alternately- (black dots) and continuously printed Ag NC patterns upon high bending strain. b Cycle test of alternately printed Ag NC patterns (upper = 1% strain; lower = 5% strain). Figure S9. Hysteresis plot of both Ag NC patterns with 1.0 % strain applied (filled circles or triangles) and released (vacant circles or triangles)

Colloidal-annealing of ZnO nanoparticles to passivate traps and improve charge extraction in colloidal quantum dot solar cells

The popularity of colloidal quantum dot (CQD) solar cells has increased owing to their tunable bandgap, multiple exciton generation, and low-cost solution processes. ZnO nanoparticle (NP) layers are generally employed as electron transport layers in CQD solar cells to efficiently extract the electrons. However, trap sites and the unfavorable band structure of the as-synthesized ZnO NPs have hindered their potential performance. Herein, we introduce a facile method of ZnO NP annealing in the colloidal state. Electrical, structural, and optical analyses demonstrated that the colloidal-annealing of ZnO NPs effectively passivated the defects and simultaneously shifted their band diagram; therefore, colloidal-annealing is a more favorable method as compared to conventional film-annealing. These CQD solar cells based on colloidal-annealed ZnO NPs exhibited efficient charge extraction, reduced recombination and achieved an enhanced power conversion efficiency (PCE) of 9.29%, whereas the CQD solar cells based on ZnO NPs without annealing had a PCE of 8.05%. Moreover, the CQD solar cells using colloidal-annealed ZnO NPs exhibited an improved air stability with 98% retention after 120 days, as compared to that of CQD solar cells using non-annealed ZnO NPs with 84% retention. © The Royal Society of Chemistry.1

Stretchable and Directly Patternable Double-Layer Structure Electrodes with Complete Coverage

Stretchable electrodes are widely used in next generation wearable electronics. Recent studies incorporated designs that help rigid electrodes attain stretchability. However, these structures exhibited unsatisfactory charge/signal extraction efficiency because of their low areal fill factor. Additionally, they cannot be photolithographically patterned on polymer substrates because of their low adhesion, requiring additional complicated fabrication steps. We developed photolithographically patternable stretchable electrodes with complete coverage and enhanced charge-extraction efficiency. The electrodes, comprising double layers, included a chemically treated Ag nanowire mesh and Au thin film. The interfacial linker role of polyvinylpyrrolidone chemically strengthened the interfacial bonds, and the reinforced concrete structure of nanowire-embedded metal thin films enhanced the mechanical properties. Therefore, the electrodes provided superior efficiency and stability in capturing physical, electromagnetic, and electrophysiological signals while exceeding the existing stretchable electrode limits. A broad range of applications are foreseen, such as electrocardiogram sensing electrodes, strain sensors, temperature sensors, and antennas.FALS