Organic light-emitting diodes (OLEDs) have become the mainstream display technology and show potential in lighting. With a constant demand of higher efficiency and longer lifetime, the design and synthesis of...
Aluminum has been extensively used as a conductor material in numerous electronic devices, including solar cells, light-emitting diodes (LEDs), organic LEDs (OLEDs), and thin-film transistors. However, its spiking surface and easy electromigration have limited its performance. To overcome this, a trace amount of nonprecious copper dopant has been proven effective in enhancing device reliability. Nevertheless, a comprehensive investigation regarding the effect of copper doping on the morphology at the aluminum conductor−organic interface is yet to be done. We had hence fabricated a series of green OLED devices to probe how copper doping affected the aluminum conductor, morphologically and electrically, and the corresponding device's efficiency and lifetime performance. We found 4 wt % copper doping to be highly effective in enabling a spike-less and smoother aluminum interface, which in turn enabled the fabrication of devices with much higher efficiency and lifetime. Specifically, the corresponding power efficacy at 1000 cd/m 2 was increased from 32 to 42 lm/W and the lifetime increased from 75 to 263 h, an increment of 250%. Atomic force microscopy confirmed that the copper doping did help smooth out the conductor interface as deposited and reduce electromigration upon operation.
Nanoparticle incorporation is a promising strategy for enhancing the performance of optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). Gold-or silver-based nanoparticles were found effective in enabling high-efficiency organic LEDs (OLEDs) in the blue or green but not red region, due to their intrinsic limited absorption bandwidth at around 520 nm. Multiple components of these precious metals were hence employed, but with limited improvement. Here, we demonstrate that a single nanoparticle based on nonprecious copper can be used to markedly enhance the efficiency of OLEDs of all colors. This nanocopper particle (NCP) exhibited an unprecedently wide absorption band, spanning from the ultraviolet (UV; ∼300 nm) to near-infrared (NIR; ∼1000 nm) region, leading to enhancement beyond the entire visible region. As a 30 nm NCP was incorporated, the maximum power efficacy (PE max )/current efficacy (CE max )/external quantum efficiency (EQE max ) were increased by 125/122/26% for a deep-blue, 6/ 23/20% for a blue, 15/15/16% for a green, 21/23/23% for a red, and 22/21/24% for a deep-red device. Our results demonstrated that an extremely wide absorption band can be achieved with the use of a single nanoparticle-based nonprecious metal, which had been found highly effective in enhancing devices in the deep-blue and deep-red regions, extending those applications in forensic and medical fields. It is believed that similar enhancements can be achieved in LEDs and solar cells etc. by using the same.
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