Gold nanostructures/quantum dots for the enhanced efficiency of organic solar cells

Incorporating gold nanoparticles (AuNPs) into organic solar cell (OSC) structures provides an effective means to manipulate light-matter interactions. AuNPs have been used as plasmonic-enhancement and light-trapping materials in OSCs and exhibit diverse single and mixed morphologies. Substantial near-field enhancement from metal periodic structures has consistently demonstrated high enhancement in solar cell efficiency. Additionally, coupling with atomic gold clusters in the form of gold quantum dots holds promise for light harvesting through fluorescence phenomena. The configured devices optimize light utilization in OSCs by considering factors such as the morphology, position, and hybridization of localized surface plasmon resonance, propagating surface plasmon resonance, and fluorescence phenomena. This optimization enhances light absorption, scattering, and efficient trapping facilitated by gold nanostructures/quantum dots. The configured setup exhibits multiple effects, concurrently improving plasmonic and fluorescence responses under solar irradiation, thereby enhancing energy conversion performance. Integrating plasmonic nanostructures with OSCs can address fundamental issues, providing opportunities to enhance the light-absorption intensity and charge transfer efficiency at intra and intermolecular levels. This comprehensive review demonstrates that the greatest improvement in solar cell efficiency exceeded 30% compared with the reference cells.

Characteristics of Dye-Sensitized Solar Cells with TiO2 Stripes

A TiO₂ strip array with a thickness of 90 nm was fabricated by photolithography and physical vapor deposition. This work utilized the chemical and physical methods to fabricate the TiO₂ strip array. A porous semiconductor layer made of TiO₂ nanoparticles was coated on the TiO₂ strip array. The TiO₂ strip array has a one-dimensional protrusive structure. The energy conversion efficiency (4.38%) of a dye-sensitized solar cell (DSSC) with the TiO₂ strip array exceeded that (3.20%) of a DSSC without a TiO₂ strip array by 37%. In addition, this result was verified by the electrochemical impedance spectra of the two DSSCs. Therefore, the TiO₂ strip array can be used to increase the energy conversion efficiencies of DSSCs. The large energy conversion efficiency of the DSSC with the TiO₂ strip array arises from the large surface area of the one-dimensional protrusive structure and its specific electron transport paths. The DSSC with the TiO₂ strip array has advantages of economical production cost, easy fabrication, and boosting energy conversion efficiency.

Dual-mode surface plasmon resonance sensor chip using a grating 3D-printed prism

The method for fabricating a grating prism surface plasmon resonance (SPR) sensor chip was developed. The grating prism was 3D-printed by a stereolithography 3D printer and subsequently created a grating pattern by soft lithography. A gold film was thermally evaporated on the grating prism. Moreover, a liquid cell was 3D-printed and assembled into a gold-coated grating prism. To make the sensor chip compact and practical, a compatible prism holder was 3D-printed by a fused deposition model 3D printer. The SPR sensor chip was mounted on the rotation stage and the SPR spectrum was recorded by spectrometer. The SPR excitation of the sensor chip can be extended to the near-infrared region by creating a grating pattern on the prism surface. A gold-coated grating prism exhibited dual modes of SPR excitations, namely, prism-coupling SPR (PC-SPR) and grating-coupling SPR (GC-SPR). The dual-mode SPR excitation was observed at the incident angles of 45°-80°. When the incident angle increased, the SPR excitation of the PC-SPR mode exhibited a blue shift in the wavelength region of 480-690 nm, whereas the GC-SPR mode exhibited a red shift in the wavelength region of 670-770 nm. The surface plasmon (SP) dispersion obtained from the dual-mode SPR configuration confirmed observable PC-SPR (which corresponded to + SP⁰ of the gold-resin interface) and GC-SPR (which corresponded to -SP⁺¹ of the gold-air interface), which could be excited from the developed substrate. The refractive index sensitivities of the PC-SPR and GC-SPR modes were 2924.4 and 414.9 nm RIU^-1, respectively. The SPR excitations of the sensor chip exhibited a simultaneous shift when the local refractive index of the materials adjacent to the gold-coated grating prism surface was changed, especially the material that had overlapping light absorption at the SPR excitation wavelength. Using this fabrication process, the prism is designed and then printed; moreover, the grating pattern on the prism surface can be employed to tune the SPR excitation wavelength of the sensor chip for the versatility and broad perspective of the optical sensing-based SPR.

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.

Extreme Enhancement of Single-Molecule Fluorescence from Porphyrins Induced by Gold Nanodimer Antennas

Porphyrins are typically weak emitters, which presents challenges to their optical detection by single-molecule fluorescence microscopy. In this contribution, we explore the enhancement effect of gold nanodimer antennas on the fluorescence of porphyrins in order to enable their single-molecule optical detection. Four meso-substituted free-base porphyrins were evaluated: two cationic, one neutral, and one anionic porphyrin. The gold nanodimer antennas are able to enhance the emission from these porphyrins by a factor of 10⁵-10⁶ increase in the maximum detected photon rates. This extreme enhancement is due to the combination of an antenna effect on the excitation rate that is estimated to be above 10⁴-fold and an emission efficiency that corresponds to an increase of 2-10 times in the porphyrin's fluorescence quantum yield.

Inverted organic solar cells enhanced by grating-coupled surface plasmons and waveguide modes

In this study, we demonstrate improved photovoltaic properties in inverted organic thin-film solar cells by simultaneous excitation of grating-coupled surface plasmons and grating-coupled waveguide modes on gold grating surfaces. The cell consists of a glass-ITO substrate/titanium dioxide/poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/gold structure. The grating structures were fabricated on P3HT:PCBM layers using a nanoimprinting technique with a PDMS stamp. The grating-structured PDMS stamps were fabricated using a DVD-R grating template with a grating pitch, Λ, of 740 nm. Reflectivity measurements made using p-polarized light clearly indicate 2 types of excitation modes, i.e., surface plasmons and waveguide modes, while s-polarized light produces only waveguide modes. Incident photon-to-current efficiency measurements exhibited increased photocurrent wavelengths corresponding to the wavelengths of surface plasmon excitations and waveguide mode excitations. Through the simultaneous excitation of surface plasmons and waveguide modes, short-circuit photocurrents in the grating-structured cells exhibited an improvement of up to 11% in the solar cells, leading to an efficiency increase of 16%.

Multi-Shaped Ag Nanoparticles in the Plasmonic Layer of Dye-Sensitized Solar Cells for Increased Power Conversion Efficiency

The use of dye-sensitized solar cells (DSSCs) is widespread owing to their high power conversion efficiency (PCE) and low cost of manufacturing. We prepared multi-shaped Ag nanoparticles (NPs) and introduced them into DSSCs to further enhance their PCE. The maximum absorption wavelength of the multi-shaped Ag NPs is 420 nm, including the shoulder with a full width at half maximum (FWHM) of 121 nm. This is a broad absorption wavelength compared to spherical Ag NPs, which have a maximum absorption wavelength of 400 nm without the shoulder of 61 nm FWHM. Therefore, when multi-shaped Ag NPs with a broader plasmon-enhanced absorption were coated on a mesoporous TiO₂ layer on a layer-by-layer structure in DSSCs, the PCE increased from 8.44% to 10.22%, equivalent to an improvement of 21.09% compared to DSSCs without a plasmonic layer. To confirm the plasmon-enhanced effect on the composite film structure in DSSCs, the PCE of DSSCs based on the composite film structure with multi-shaped Ag NPs increased from 8.58% to 10.34%, equivalent to an improvement of 20.51% compared to DSSCs without a plasmonic layer. This concept can be applied to perovskite solar cells, hybrid solar cells, and other solar cells devices.

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.

Ammonia Gas Detection under Various Humidity Conditions Using Waveguide Surface Plasmon Resonance Spectroscopy

Analysis of NH₃ gas under various humidity conditions was conducted using a waveguide surface plasmon resonance (SPR) sensor with dual sensing parts. Two pairs of Ag films/sensing polymer films were prepared separately on a waveguide core of BK-7 slide glass. Poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) were used as sensing materials. A white light was guided through the core by illuminating the substrate edge, and the SPR property was investigated by observing the output light spectrum. The thicknesses of PAA and PVA films were adjusted to induce SPR at different wavelengths. PAA exhibited remarkable response against NH₃ gas, but it also exhibited a strong dependence on humidity. In contrast, PVA responded to humidity but hardly responded to NH₃ gas below 20 ppm. The dual sensing would allow us to conduct precise NH₃ measurements under various humidity conditions.

Surface plasmon-enhanced dye-sensitized solar cells based on double-layered composite films consisting of TiO2/Ag and TiO2/Au nanoparticles

Double-layered composite films consisting of TiO₂/Ag and TiO₂/Au nanoparticles.

Panchromatic quasi-monolayer of Ag nanoparticles for high-efficiency dye-sensitized solar cells

We developed a panchromatic quasi-monolayer of Ag NPs and applied this technique to fabricate DSSCs.

Plasmonic cooperation effect of metal nanomaterials at Au–TiO2–Ag interface to enhance photovoltaic performance for dye-sensitized solar cells

Au and Ag nanoparticles enhance electric energy conversion by a strong plasmonic cooperation effect and complementary light absorption.

In situ electrochemical-transmission surface plasmon resonance spectroscopy for poly(pyrrole-3-carboxylic acid) thin-film-based biosensor applications

In this study, we describe the combination of transmission surface plasmon resonance (TSPR) and electrochemical techniques for the application to biosensors with conducting polymers. Electropolymerization was employed to construct poly(pyrrole-3-carboxylic acid) (PP3C) film on a gold-coated grating substrate using pyrrole-3-carboxylic acid (P3C) monomer solution in 0.5 M H(2)SO(4). In situ electrochemical-transmission surface plasmon resonance (EC-TSPR) measurements were carried out to study the kinetic and electroactivity properties of PP3C film. Immobilization of antihuman IgG on the activated surface and the binding process of human IgG and antihuman IgG in neutral solution could be detected in situ by EC-TSPR measurement. The surface modification steps on the PP3C layer led to an increase in intensity of the transmission peak. The performance, sensitivity, and utility of EC-TSPR spectroscopy showed obvious advantages for the detection of binding process with the simple experimental setup, and could be applied to the study of biomolecular interactions in various systems.