Enhancement of organic solar cell performance by incorporating gold quantum dots (AuQDs) on a plasmonic grating.

The incorporation of metallic nanoobjects into devices allows to increase light harvesting, which increases the device performance. In this study, we used a combination of gold quantum dots and grating-coupled surface plasmon resonance (GCSPR) to improve the performance of organic solar cells (OSCs) with a poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM) photoactive layer. Gold quantum dots with a green fluorescent color (green-AuQD) were loaded into a hole transport layer (HTL) aiming to harvest photons in the UV region and emit visible light into the neighboring photoactive layer. Meanwhile, plasmonic grating structures, which were created on the photoactive layer surfaces via the nanoimprinting technique, provided an enhancement effect through light scattering and GCSPR. Thus, an excellent enhancement of OSC efficiency with a significant increase in short circuit photocurrent (J SC) and power conversion efficiency (PCE) in comparison to that of the reference cell was achieved. The fabricated device provides a J SC value as high as 8.41 mA cm-2 (a 14.11% enhancement) and a PCE value of 3.91% (a 19.57% enhancement). The systematic study clearly reveals that the remarkable enhancement of OSC efficiency is achieved by incorporating both AuQD and plasmonic grating.

Fabrication of Miniature Surface Plasmon Resonance Sensor Chips by Using Confined Sessile Drop Technique.

In this study, we demonstrate a simple and efficient method to fabricate miniature surface plasmon resonance (SPR) sensor chips by using confined sessile drop technique. A liquid optical adhesive (NOA 61) was dropped on the circular flat surface of cylindrical substrates made of poly(dimethylsiloxane) (PDMS). The formation of hemispherical optical prisms was accomplished by taking advantage of the sharp edges of cylindrical PDMS substrates that prevented the overflow of liquid NOA 61 at the edge of substrates. The size of the hemispherical optical prisms can be controlled by changing the diameter of the cylindrical PDMS substrates. After UV curing, the SPR sensor chips were obtained by the deposition of 3 nm thick chromium and 47 nm thick gold on the flat side of the prisms. The fabricated miniature SPR sensor chips were then mounted on a three-dimensional-printed flow cell to complete the microfluidic SPR sensor module. The miniature SPR sensor chips provided a comparable sensitivity to the conventional high-refractive-index glass SPR chips. To demonstrate the detection capability of nanometer-sized materials, we applied the miniature microfluidic SPR system for monitoring the deposition of layer-by-layer ultrathin films of poly(diallyldimethylammonium chloride)/poly(sodium 4-styrenesulfonate) and for detecting human immunoglobulin G.

Plasmonic-Enhanced Photocurrent Generation of Organic Photovoltaics Induced by 1D Grating and 2D Crossed Grating Structures.

In this work, plasmonic-enhanced photocurrent generation in organic photovoltaic (OPV) devices is demonstrated. One-dimensional (1D) and two-dimensional (2D) crossed grating structures are created on the active-layer surface composed of a blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) via a nanoimprinting technique using a template of a Blu-ray disc recordable (BD-R) grating structure. After formation of aluminum back electrodes, the grating-coupled surface plasmon (GCSPR) and light scattering observed in the devices with grating structures provide a 12.3% and 11.0% enhancement of the photocurrent for the devices with 1D grating and 2D crossed grating structures, respectively. The OPV devices with the 2D crossed grating show a plasmonic-enhanced photocurrent under irradiation with light with all polarization directions, whereas those with the 1D grating provide plasmonic enhancement only under illumination with p-polarized light.

Grating-coupled surface plasmon resonance enhanced organic photovoltaic devices induced by Blu-ray disc recordable and Blu-ray disc grating structures.

In this work, we studied the performance enhancement of organic thin-film solar cells (OSCs) originating from the presence of diffraction gratings on the surface of the active layer. Two types of diffraction gratings, periodic gratings (Blu-ray disc recordable: BD-R) and quasi-random gratings (Blu-ray disc: BD), were employed as master templates for grating structures. The grating structures were introduced to the surfaces of poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) films, which were the active layers of the solar cells. The addition of the grating structures led to an increase of light absorption in the absorption region of P3HT:PCBM induced by light scattering. Furthermore, the grating-coupled surface plasmon resonance generated additional light absorption peaks. With illumination of non-polarized light at a normal incident angle, the short-circuit current densities of the BD-R and BD solar cells improved by 11.05% and 10.6%, respectively. Efficiency improvements of 19.28% and 3.21% were also observed for the BD-R and BD devices, respectively. Finally, the finite-difference time-domain simulation results revealed an enhanced electric field in the P3HT:PCBM layer, especially in the BD-R OSC devices.

Effect of urchin-like gold nanoparticles in organic thin-film solar cells.

In this study, urchin-like gold nanoparticles (UL-AuNPs) are used in the fabrication of organic thin-film solar cells (OSCs). UL-AuNPs, which have gold nanothorns on their surface, enhance light accumulation by acting as light-trapping materials. This is due to the enhanced electric field and light scattering attributed to the nanothorns on the surface of the nanoparticles. UL-AuNPs were incorporated into a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT: PSS) thin-film layer of organic thin-film solar cells (OSCs). UV-vis spectra, atomic force microscopy (AFM) images, current density versus voltage properties, and the impedance spectra of the fabricated devices were recorded at various concentrations of UL-AuNPs. We found that the efficiency of the OSCs with UL-AuNPs was not only higher than that of a reference cell without nanoparticles but also higher than that of OSCs with spherical AuNPs. Finite-difference time-domain (FDTD) simulation indicated that the electric field around the UL-AuNPs increased due to the presence of nanothorns.

Investigation of localized surface plasmon/grating-coupled surface plasmon enhanced photocurrent in TiO2 thin films.

We fabricated plasmonic gold nanoparticle (AuNP)-TiO2 nanocomposite films and measured the photocurrent that originates from the water-splitting reaction catalyzed by the AuNP-TiO2 nanocomposite photoelectrocatalytic (PEC) electrode. The localized surface plasmon resonance (LSPR) of the gold nanoparticles affected the generation of photocurrent by TiO2 upon illumination with visible light. Electrochemical impedance spectroscopy (EIS) revealed that the improvement in the photocurrent generation originates from an enhancement in electron-hole pair generation induced by the SPR of the plasmonic gold nanoparticles rather than the extension of the electron lifetime. Moreover, we introduced a novel method to enhance the photocurrent of TiO2 by a multiple plasmonic effect, i.e., LSPR of plasmonic gold nanoparticles and the grating-coupled propagating SP on a gold grating. We fabricated the AuNP-TiO2 nanocomposites on a gold-coated Blu-ray disc recordable (BD-R). The enhancement of the photocurrent due to the combination of LSPR and the grating-coupled SP was investigated.