Advances in flexible optoelectronic devices have led to an increasing need for developing highly efficient, low-cost, flexible transparent conducting electrodes. Copper-based electrodes have been unattainable due to the relatively low optical transmission and poor oxidation resistance of copper. Here, we report the synthesis of a completely continuous, smooth copper ultra-thin film via limited copper oxidation with a trace amount of oxygen. The weakly oxidized copper thin film sandwiched between zinc oxide films exhibits good optoelectrical performance (an average transmittance of 83% over the visible spectral range of 400–800 nm and a sheet resistance of 9 Ω sq−1) and strong oxidation resistance. These values surpass those previously reported for copper-based electrodes; further, the record power conversion efficiency of 7.5% makes it clear that the use of an oxidized copper-based transparent electrode on a polymer substrate can provide an effective solution for the fabrication of flexible organic solar cells.
Copper has attracted significant interests as an abundant and low‐cost alternative material for flexible transparent conducting electrodes (FTCEs). However, Cu‐based FTCEs still present unsolved technical issues, such as their inferior light transmittance and oxidation durability compared to conventional indium tin oxide (ITO) and silver metal electrodes. This study reports a novel technique for fabricating highly efficient FTCEs composed of a copper ultrathin film sandwiched between zinc oxides, with enhanced transparency and antioxidation performances. A completely continuous and smooth copper ultrathin film is fabricated by a simple room‐temperature reactive sputtering process involving controlled nitrogen doping (<1%) due to a dramatic improvement in the wettability of copper on zinc oxide surfaces. The electrode based on the nitrogen‐doped copper film exhibits an optimized average transmittance of 84% over a spectral range of 380 −1000 nm and a sheet resistance lower than 20 Ω sq−1, with no electrical degradation after exposure to strong oxidation conditions for 760 h. Remarkably, a flexible organic solar cell based on the present Cu‐based FTCE achieves a power conversion efficiency of 7.1%, clearly exceeding that (6.6%) of solar cells utilizing the conventional ITO film, and this excellent performance is maintained even in almost completely bent configurations.
Epoxy
polymer-based dielectric materials play a crucial role in
advanced electronic devices and power equipment. However, high voltage-stress
applications impose stringent requirements, such as a high dielectric
strength, on epoxy polymers. Previously reported studies have shown
promising material architectures in the form of epoxy polymer–nanoparticle
dielectrics, which can restrict the movement of high-energy electrons
by the interface charge traps associated with the various interfacial
regions. However, these high-energy electrons inevitably traverse
the epoxy polymer matrix and destroy the molecular structure, thereby
creating a weak link for dielectric breakdown. In this study, a general
strategy is developed to improve the dielectric strength by constructing
interface charge traps in the molecular structure of the epoxy polymer
matrix, using the −CF3 group in partial replacement
of the −CH3 group. The proposed strategy increases
the dielectric strength (39.5 kV mm–1) and surface
breakdown voltage (26.9 kV) of the epoxy polymer matrix by 22.08%
and 13.3%, respectively, because the interface charge trap hinders
the movement of high-energy electrons. At the same time, the strategy
does not degrade the mechanical and thermal properties. The results
hold potential for wide application in the manufacturing of advanced
future electrical and electronic equipment requiring resilience to
high-voltage stress.
Chronic ethanol consumption affects adipokine levels in VAT and sera in a dose-dependent manner, with the exception of serum cartonectin. The altered levels of adipokines in VAT and sera are positively correlated.
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