Copper Nanoparticles Enhancing Organic Light-Emitting Diodes of All Colors

Nanoparticle incorporation is a promising strategy forenhancingthe performance of optoelectronic devices, such as solar cells andlight-emitting diodes (LEDs). Gold- or silver-based nanoparticleswere found effective in enabling high-efficiency organic LEDs (OLEDs)in the blue or green but not red region, due to their intrinsic limitedabsorption bandwidth at around 520 nm. Multiple components of theseprecious metals were hence employed, but with limited improvement.Here, we demonstrate that a single nanoparticle based on nonpreciouscopper can be used to markedly enhance the efficiency of OLEDs ofall colors. This nanocopper particle (NCP) exhibited an unprecedentlywide absorption band, spanning from the ultraviolet (UV; similar to 300nm) to near-infrared (NIR; similar to 1000 nm) region, leading to enhancementbeyond the entire visible region. As a 30 nm NCP was incorporated,the maximum power efficacy (PEmax)/current efficacy (CEmax)/external quantum efficiency (EQE(max)) were increasedby 125/122/26% for a deep-blue, 6/23/20% for a blue, 15/15/16% fora 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 canbe achieved with the use of a single nanoparticle-based nonpreciousmetal, which had been found highly effective in enhancing devicesin the deep-blue and deep-red regions, extending those applicationsin forensic and medical fields. It is believed that similar enhancementscan be achieved in LEDs and solar cells etc. by using the same.