A new polymer solar cells designed by researchers at the Ulsan National Institute of Science and Technology has achieved a record for the highest efficiency of any plasmonic PSCs that utilize metal nanoparticles. The new record is not far off of the 10% conversion efficiency level that the researchers think will allow the technology to break through into the commercial market.
For some background: Polymer solar cells (PSCs) are a type of thin-film solar cell that are manufactured out of polymers that create electricity via the photovoltaic effect. As of right now, the solar energy market is dominated by silicon solar cells. But there are other types of solar cells, and some have significant advantages over the silicon type, such as PSCs. PSCs are lightweight, relatively inexpensive to fabricate, flexible, customizable on the molecular level, and it’s been argued that they would have a lower negative environmental impact than silicon solar cells do (which already have a minimal environmental impact compared to electricity generation competitors).
But there are obviously still barriers to their commercialization, the primary of which is that their power conversion efficiency is still too low. The upsides to the technology are significant enough, though, that a lot of time and research has gone into addressing the relatively low efficiencies, hence the new record.
The press release from the Ulsan National Institute of Science and Technology (UNIST) gets into the specifics of the new solar cell design:
To maximize PCE, light absorption in the active layer has to be increased using thick bulk heterojunction (BHJ) films. However, the thickness of the active layer is limited by the low carrier mobilities of BHJ materials. Therefore, it is necessary to find the ways to minimize the thickness of BHJ films while maximizing the light absorption capability in the active layer.
The research team employed the surface plasmon resonance (SPR) effect via multi-positional silica-coated silver NPs (Ag@SiO2) to increase light absorption. The silica shell in Ag@SiO2 preserves the SPR effect of the Ag NPs by preventing oxidation of the Ag core under ambient conditions and also eliminates the concern about exciton quenching by avoiding direct contact between Ag cores and the active layer. The multi-positional property refers to the ability of Ag@SiO2 NPs to be introduced at both ITO/PEDOT:PSS (type I) and PEDOT:PSS/active layer (type II) interfaces in polymer: fullerene-based BHJ PSCs due to the silica shells.
Jin Young Kim and Soojin Park, both Associate Professors of the Interdisciplinary School of Green Energy at the Ulsan National Institute of Science and Technology (UNIST) in Ulsan, South Korea, led this work.
Professor Jin Young Kim, an associate professor of the Interdisciplinary School of Green Energy at UNIST, said: “This is the first report introducing metal NPs between the hole transport layer and active layer for enhancing device performance. The multipositional and solutions-processable properties of our surface plasmon resonance (SPR) materials offer the possibility to use multiple plasmonic effects by introducing various metal nanoparticles into different spatial location for high-performance optoelectronic device via mass production techniques.”
Professor Soojin Park, added: “Our work is meaningful to develop novel metal nanoparticles and almost reach 10% efficiency by using these materials. If we continuously focus on optimizing this work, commercialization of PSCs will be a realization but not dream.”