EAGER: Plasmonic Transparent Electrodes for Organic Photovoltaics

Lehigh University, Bethlehem PA

Investigators

Abstract

Abstract: Nontechnical: Photovoltaic devices have the potential to provide an unlimited source of energy by converting solar light into electricity. Photovoltaic devices made with organic materials offer significant advantages compared to ones made with inorganic materials. These advantages include low-cost, light-weight, flexibility, and compatibility with reel-to-reel high-volume processing. However, widespread adoption of organic photovoltaic devices is limited by their relatively low power conversion efficiency, and the poor mechanical properties of the currently used indium-tin-oxide transparent electrode, especially for flexible devices. The brittleness of indium-tin-oxide thin films may render them incompatible with low cost, reel-to-reel, high volume processing and manufacturing of flexible organic solar cells. This EAGER project will investigate novel plasmonic nanostructured transparent electrodes as replacement for the currently used indium-tin-oxide transparent electrodes in organic solar cells. The new plasmonic transparent electrodes will significantly enhance the photon absorption in the organic light-harvesting layer(s) and thus improve the power conversion efficiency of the organic-based solar cells. The concept of taking advantage of the dual nature of the proposed plasmonic nanostructures is novel and transformative as it will enable the replacement of indium-tin-oxide with a material not only more superior as a transparent electrode but with an additional crucial function, which will boost the device power conversion efficiency and lead to large-scale manufacturing of low cost photovoltaic devices. This project will contribute to building US competitiveness in the field of renewable energy sources. Technical: This project will investigate novel metallic nanostructures in which the decay length of surface plasmon resonances is of the same order of magnitude as the thickness of the organic light-harvesting layer(s). These novel transparent electrodes have been shown via simulations to yield the highest reported enhancement in total photon absorption of the organic active light-harvesting layer(s) in an organic photovoltaic device. Two different types (single- and double-sided) of plasmonic nanostructures will be investigated and, various geometries from each type will be studied and compared to prior simulation results. An integrated experimental set-up will be used to prevent any air/moisture exposure of the silver electrode and of the organic materials during device processing and characterization. Two different lithographic techniques imprint and stencil will be pursued in order to realize the plasmonic nanostructured electrodes in organic photovoltaic devices. This project will seek to measure experimentally the enhanced photon absorption and demonstrate that it can be translated into an increased short-circuit current density resulting in a significantly enhanced power conversion efficiency. Unravelling the physics and the mechanism(s) that result in such an enhancement, and identifying any bottlenecks that may interfere with them, will advance our knowledge and understanding of the interactions between plasmonic and organic nanostructures. This will enable the proposed plasmonic transparent electrodes to be implemented in other thin film optoelectronic devices, such as organic biosensors, thus opening the door for many other applications and enabling technologies. The PI at Lehigh University has the track record in recruiting minorities and will continue to provide opportunities for underrepresented groups in the summer programs. The PI also plans to pursue NSF-REU (Research Experience for Undergraduates) to foster undergraduate participation with an emphasis on minority student recruitment.