Fabrication and Characterization of Three-Dimensional Plasmonic Devices Utilizing Aerosol-Derived Nanoparticles

Abstract

In this study I applied bottom-up type dry aerosol technology to fabricate plasmonic devices such as organic solar cells and surface-enhance Raman scattering (SERS) by constructing nanoparticle-assembled three-dimensional nanoarchitecture platform.

Firstly, I have demonstrated a considerable enhancement both in JSC and PCE of the plasmonic PCDTBT : PC70BM solar cells employing the NBA composed of MoO3 layer and Ag NPs under the active layer, compared to the reference devices including MoO3 hole extraction layer(HEL) without nanoparticles (NPs). Here, the NPs with different diameters (Ag 20, 40, and 60 nm) have been generated by the evaporation and condensation method using the aerosol process in dry environment without aggregation, impurity, and contamination issues that can usually happen in the wet synthesis. Finite-difference time domain (FDTD) calculation results on scattering cross-sections and near field profiles inside the active materials show higher intensities with a strong forward scattering effect in the devices with the nanobump assembly (NBA) than those with the flat PEDOT:PSS. J-V characteristics show that JSC increases continuously as the size of NPs increases and the best performance is achieved at the device embedding NBA-40. The improved performance depending on the size of NPs is explained by the strong forward light scattering effect coming from near-field enhancement in the vicinity of Ag NP in the visible region, as well as the multi-reflection between the cathode and the nanobump anode in the near IR region. Therefore, this approach can be a promising platform for efficient light harnessing in a broad spectral range for use in diverse OPV devices.

Secondly, I studied 3D mesoscopic multipetal flowers assembled by metallic nanoparticles as a SERS substrate. Seven orders of SERS enhancement, sufficiency for single molecule detection, and multiresonance features in whole visible frequency range were achieved by plasmonic hot-spot engineering through increasing the number of petals from four to eight. By performing DF imaging, spectrum measurements, and FEM analysis I addressed that hot-spots and multipole resonance modes are responsible for peculiar optical properties of multipetal flower structures. Because the nanofabrication technique based on atmospheric spark discharge and electrostatic parallel focusing has capability to construct well-defined, uniform, and reproducible 3D nanostructures in wafer scales, it can not only open the way for manufacturing a reliable 3D SERS substrate sufficient for single molecule detection, but apply to a broad range of novel plasmonic devices. To conclude, novel 3D plasmonic devices utilizing aerosol-derived metal nanoparticles were demonstrated, which would pave the way for the future development of diverse nanoscale optoelectric devices with maneuvering their surface plasmon traits in a broad spectral range.