ABSTRACT
Percolation networks of one-dimensional (1D) building blocks (e.g., metallic nanowires or carbon nanotubes) represent the mainstream strategy to fabricate stretchable conductors. One of the inherent limitations is the control over junction resistance between 1D building blocks in natural and strained states of conductors. Herein, we report highly stretchable transparent strain-insensitive conductors using fractal gold (F-Au) nanoframework based on a one-pot templateless wet chemistry synthesis method. The monolayered F-Au nanoframework (â¼20 nm in thickness) can be obtained from the one-pot synthesis without any purification steps involved and can be transferred directly to arbitrary substrates like polyethylene terephthalate, food-wrap, polydimethylsiloxane (PDMS), and ecoflex. The F-Au thin film with no capping agents leads to a highly conductive thin film without any post-treatment and can be stretched up to 110% strain without significantly losing conductivity yet with the optical transparency of 70% at 550 nm. Remarkably, the F-Au thin film shows the strain-insensitive behavior up to 20% stretching strain. This originates from the unique fractal nanomesh-like structure which can absorb external mechanical forces, thus maintaining electron pathways throughout the nanoframework. In addition, a semitransparent bilayered F-Au film on 100% prestrained PDMS could achieve to a high stretchability of 420% strain with negligible resistance changes under low-level strains.
ABSTRACT
About 30 nm quantum-dot thin films are formed by electrospray deposition (ESD) process and quantum-dot-light-emitting-diodes (QD-LEDs) are demonstrated. Maximum brightness of 23 000 cd m(-2) and current efficiency of 5.9 cd A(-1) are achieved with the ESD process. The ESD process can be a potential solution for large area quantum dot layers with simple and flexible control.
ABSTRACT
The performance of quantum dot light-emitting diodes (QD-LEDs) was investigated for different hole transport layers with small molecules and polymers: poly(4-butyl-phenyl-diphenyl-amine), poly-N-vinylcarbazole (PVK), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine, 4,4',4â³-tris(N-carbazolyl)-triphenyl-amine (TCTA), and 4,4'-bis(carbazole-9-yl)biphenyl (CBP). The electroluminescence performance of QD-LEDs was considerably improved by adding small molecules (TCTA or CBP) having high hole mobilily to the polymer hole transport material (PVK). The maximal current efficiency of QD-LED-based PVK was improved by 27% upon addition of 20 wt % TCTA due to the hole injection improvement. The lower turn-on voltage, the higher current density, and the higher luminance were achieved by addition of TCTA. The maximal luminance of 40900 cd/m(2) and the highest current efficiency of 14.0 cd/A with the narrow full width at half-maximum (<35 nm) were achieved by the best hole transport layer.
