Copper Nanoparticles Enhancing Organic Light-Emitting Diodes of All Colors

Abstract

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.