Polymer Solar Cell Efficiency Hits 8.9 Percent

The highly purified silicon crystal used in today's commercial solar cells could be replaced with more economical, disposable, polymer-based materials if their efficiency and stability could be improved. A team at Ulsan National Institute of Science and Technology (UNIST) believes it has done just that, reporting the highest device efficiencies to date for plasmonic polymer solar cells using metal nanoparticles.

(a) Device structures, (b) J-V characteristics, and (c) EQE of PTB7:PC70BM-based PSCs with type I and type II architectures. Courtesy of UNIST.

Compared with silicon-based devices, polymer solar cells (PSCs) are lightweight (important for small autonomous sensors), potentially disposable, inexpensive to fabricate, flexible, and customizable on the molecular level. But they lack a high enough efficiency for large-scale applications and have stability problems. Still, their promise of extremely cheap production and high efficiency has led to polymer cells becoming one of the most popular fields in solar cell research.

The UNIST team used the surface plasmon resonance effect via multipositional silica-coated silver nanoparticles (NPs) to increase light absorption. The device incorporating nanoparticles between the hole transport layer and the active layer achieved a power conversion efficiency of 8.9 percent, with an external quantum efficiency of 81.5 percent, the researchers reported, adding, "We should break the efficiency barrier of 10 percent for commercialization of PSCs."

The work was led by Jin Young Kim and Soojin Park, both associate professors at Ulsan's Interdisciplinary School of Green Energy.

"This is the first report introducing metal NPs between the hole transport layer and active layer for enhancing device performance," Kim said. "The multipositional and solutions-processable properties of our surface plasmon resonance materials offer the possibility to use multiple plasmonic effects by introducing various metal nanoparticles into different spatial location for high-performance optoelectronic devices via mass production techniques."

"If we continuously focus on optimizing this work, commercialization of PSCs will be a realization ... not a dream," Park added.

The work appears in Nano Letters doi: 10.1021/nl400730z.

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