Plasmonics Gives Performance Boost to Polymer LEDs, Solar Cells

A new plasmonic material based on carbon dot-supported silver (CD-Ag) nanoparticles, which produce a surface plasmon resonance effect, has boosted the performance of polymer LEDs (PLEDs) and polymer solar cells (PSCs) while keeping their structure simple.

Most semiconducting optoelectronic devices (OEDs), including solar cells, LEDs, photodiodes and semiconductor lasers, are based on inorganic materials, but because of the limited availability of raw materials and the complex processing required to manufacture such OEDs, the cost of device fabrication has increased.

Organic semiconductor devices are cheaper to make than inorganic ones, but further improvements in efficiency are needed before there can be widespread commercialization of these technologies. Plasmonic nanoparticles can boost efficiency; however, the contrary demands of PLEDs and PSCs mean that there are few metal nanoparticles that can enhance the performance in PLEDs and PSCs at the same time.

The research group of professors Jin Young Kim (front left) and Byeong-Su Kim (front right). Courtesy of ©UNIST.

The material prepared at Ulsan National Institute of Science and Technology (UNIST) is easy to synthesize with basic equipment and has low-temperature solution processability, enabling roll-to-roll mass-production techniques suitable for printed electronic devices.

“Our work is significant also because it anticipates the realization of electrically driven laser devices by utilizing carbon dot-supported silver nanoparticles as plasmonic materials,” said professor Byeong-Su Kim. “The material allows significant radiative emission and additional light absorption, leading to remarkably enhanced current efficiency.”

The team demonstrated PLEDs that achieved high current efficiency from 11.65 to 27.16 cd/A⁻¹ and luminous efficiency (LE) from 6.33 to 18.54 lm/W⁻¹. PSCs produced in this way showed enhanced power-conversion efficiency from 7.53 to 8.31 percent and internal quantum efficiency (IQE) from 91 to 99 percent at 460 nm. The LE and IQE are among the highest values reported to date in fluorescent PLEDs and PSCs, respectively, the investigators say.

The synthesis of the carbon dot-supported silver nanoparticles (CD-Ag NPs) and structures of plasmonic PLED/PSC with CD-Ag NPs. Courtesy of UNIST.

“These significant improvements in device efficiency demonstrate that surface plasmon resonance materials constitute a versatile and effective route for achieving high- performance polymer LEDs and polymer solar cells,” said professor Jin Young Kim. “This approach shows promise as a route for the realization of electrically driven polymer lasers.”

Scientists from Chungnam and Pusan national universities, and Gwangju Institute of Science and Technology also contributed to the research, which appeared in Nature Photonics (doi: 10.1038/nphoton.2013.181).

For more information, visit: www.unist.ac.kr