On April 29, KAIST announced that Professor Jung-Yong Lee from the Graduate School of Energy, Environment, Water and Sustainability developed a technology that can increase the power conversion efficiency (PCE) of the organic photovoltaic (OPV) cells up to 20 percent. Furthermore, the research team identified for the first time the plasmonic scattering effect as the origin of efficiency enhancement.
The silicon solar cells currently in use are economically infeasible. The OPV cells are considered as the next-generation solar cells for they are lightweight, flexible, and cheap. To commercialize these cells, however, the relatively low PCE needs to be enhanced. Many research groups around the world have been trying to develop new polymer materials that can achieve high PCE, but the ultrathin film thickness has made it difficult to overcome low light absorption and hence poor efficiency.
Professor Lee’s research team incorporated size-controlled silver nanoparticles with diameters of 10 to 100 nm into the OPV cells. The optical properties of the nanoparticles considerably improved the performance levels - PCE increased from 6.4% to 7.6% in one type and from 7.9% to 8.6% in another type. Through visualization with the near-field optical microscopy and analytic optical simulations, the research team also proved that the size-dependent plasmonic forwarding scattering effect of the silver nanoparticles is the cause of the increase in efficiency; the exact mechanism of the improvement was not well understood up until now.
Professor Lee commented that the study demonstrates the possibility of manipulating the plasmonic optical properties as a powerful engineering tool. The newly developed technology is easily applicable to large-scale solar cell production because the silver nanoparticles are synthesized through low-cost methods. He added that this practical technology would make huge contributions to the commercialization of OPV cells.
On April 25, the results of the study were published on online issue of Scientific Reports, a primary research publication from the publishers of Nature. The research team led by Professor Lee included doctoral candidate Se-Woong Baek.