Plasmonics boosts performance in polymer LEDs, solar cells
Using carbon-dot-supported silver nanoparticles to produce a surface plasmon resonance effect can boost the performance of both polymer LEDs (PLEDs) and polymer solar cells (PSCs) while keeping their structure simple.
Most semiconducting optoelectronic devices – including solar cells, LEDs, photodiodes and semiconductor lasers – are based on inorganic materials. But these raw materials have limited availability and require complex processing, so these devices can be expensive to fabricate. Organic semiconductor devices are cheaper to make than inorganic ones, but further improvements in efficiency are needed before widespread commercialization can be achieved.
Plasmonic nanoparticles can boost efficiency, but 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 new material, prepared at Ulsan National Institute of Science and Technology, 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.
The synthesis of the carbon-dot-supported silver nanoparticles (CD-Ag NPs) and structures with CD-Ag NPs. (a) Photographs and schematic illustration of AgNO3 and CD+AgNO3 blend solutions before (left) and after (right) UV irradiation. (b) Transmission electron microscope image of CD-Ag NPs; the white and red circles indicate the presence of CDs and silver NPs, respectively. (c) Comparison of UV-VIS absorption spectra of CD-Ag NPs in solution and in a film, and CDs and AgNO3 solutions after UV irradiation. (d) Polymer LED structure. (e) Polymer solar cell structure. Photo courtesy of UNIST
“The material allows significant radiative emission and additional light absorption, leading to remarkably enhanced current efficiency,” said professor Byeong-Su Kim.
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 values are among the highest reported to date in fluorescent PLEDs and PSCs, respectively.
“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 as well as Gwangju Institute of Science and Technology also contributed to the research, which appeared in Nature Photonics (doi: 10.1038/nphoton.2013.181).
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