Synergistic plasmonic effects of metal nanoparticle-decorated PEGylated graphene oxides in polymer solar cells

Enhancing the Performance of Wide-Bandgap Polymer-Based Organic Solar Cells through Silver Nanorod Integration

Light trapping induced by the introduction of metallic nanoparticles has been shown to improve photo absorption in organic solar cells (OSCs). Researchers in the fields of plasmonics and organic photovoltaics work together to boost sunlight absorption and photon-electron interactions in order to improve device performance. In this contribution, an inverted OSC was fabricated by using indacenodithieno[3,2-b]thiophene-alt-2,2'-bithiazole (PIDTT-BTz) as a wide-band gap donor copolymer and (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor. Silver nanorods (Ag-NRs), synthesized by precipitation method, were embedded in the active layer of the solar cell. The device fabricated with 1 wt % Ag-NRs in the active layer showed a 26% improvement in power conversion efficiency (PCE) when exposed to 100 mW/cm2 simulated solar illumination. The role of Ag-NRs in the performance improvement of the OSCs was analyzed systematically using morphological, electrical, and optical characterization methods. The light trapping and exciton generation were improved due to the localized surface plasmon resonance (LSPR) activated in Ag-NRs in the form of longitudinal and transverse modes. The photoactive layers (PIDTT-BTz:PC71BM) with the incorporation of 0.5 and 1 wt % Ag-NR showed increased absorption, while the absorption with 1.5 wt % Ag-NRs appeared to be reduced in the wavelength range from 400 to 580 nm. Ag-NRs play a favorable role in exciton photogeneration and dissociation due to the two LSPR modes generated by the Ag-NRs. In the optimized device, the short-circuit current density (JSC) increased from 11.92 to 14.25 mA/cm2, resulting in an increase in the PCE from 3.94 to 4.93%, which is attributed to the improved light-trapping by LSPR using Ag-NRs.

Enhancing photoluminescence performance of perovskite quantum dots with plasmonic nanoparticles: insights into mechanisms and light-emitting applications

Perovskite quantum dots (QDs) are considered as promising materials for numerous optoelectronic applications due to their narrow emission spectra, high color purity, high photoluminescence quantum yields (PLQYs), and cost-effectiveness. Herein, we synthesized various types of perovskite QDs and incorporated Au nanoparticles (NPs) to systematically investigate the impact of plasmonic effects on the photoluminescence performance of perovskite QDs. The PLQYs of the QDs are enhanced effectively upon the inclusion of Au NPs in the solutions, with an impressive PLQY approaching 99% achieved. The PL measurements reveal that the primary mechanism behind the PL improvement is the accelerated rate of radiative recombination. Furthermore, we integrate perovskite QDs and Au NPs, which function as color conversion layers, with blue light-emitting diodes (LEDs), achieving a remarkable efficiency of 140.6 lm W-1. Additionally, we prepare photopatternable thin films of perovskite QDs using photocrosslinkable polymers as the matrix. Microscale patterning of the thin films is accomplished, indicating that the addition of plasmonic NPs does not adversely affect their photopatternable properties. Overall, our research not only elucidates the underlying mechanisms of plasmonic effects on perovskite QDs but presents a practical method for enhancing their optical performance, paving the way for next-generation optoelectronic applications, including high-definition micro-LED panels.

Application of Graphene-Related Materials in Organic Solar Cells

Graphene-related materials (GRMs) such as graphene quantum dots (GQDs), graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoribbons (GNRs), and so forth have recently emerged as photovoltaic (PV) materials due to their nanodimensional structure and outstanding properties such as high electrical and thermal conductivity, large specific surface, and unique combination of mechanical strength and flexibility. They can be a crucial part of transparent electrodes, hole/electron transport materials, and active layers in organic solar cells (OSCs). Besides their role in charge extraction and transport, GRMs act as device protectors against environmental degradation through their compact bidimensional structure and offer good durability. This review briefly presents the synthesis methods of GRMs and describes the current progress in GRM-based OSCs. PV parameters (short circuit current, open circuit voltage, power conversion efficiency, and fill factor) are summarized and comparatively discussed for the different structures. The efficiency recently surpassed 15% for an OSC incorporating polymer-modified graphene as a transparent electrode. The long-term stability of OSCs incorporating GRMs is also discussed. Finally, conclusions and the outlook for future investigation into GRM-based devices for PVs are presented.

Position Effects of Metal Nanoparticles on the Performance of Perovskite Light-Emitting Diodes

Metal nanoparticles have been widely used for improving the efficiencies of many optoelectronic devices. Herein, position effects of gold nanoparticles (Au NPs) on the performance of perovskite light-emitting diodes (PeLEDs) are investigated. Amphiphilic Au NPs are synthesized so that they can be incorporated into different layers of the PeLEDs to enhance device efficiencies. The photoluminescent (PL) studies indicate apparent position effects; the strongest PL intensity occurs when the NPs are directly blended with the light-emitting perovskite layer. In contrast, the PeLEDs exhibit the highest luminance efficiency while the Au NPs are placed in the hole-transporting layer. The direct blending of the NPs in the perovskite layer might affect the electrical properties, resulting in inferior device performance. The results reported herein can help to understand the enhancing mechanism of the PeLEDs and may also lead to even better efficiencies in the near future.

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.

Investigation of a gold quantum dot/plasmonic gold nanoparticle system for improvement of organic solar cells

Light management allows enhancement of light harvesting in organic solar cells (OSCs). In this paper, we describe the investigation of OSCs enhanced by the synergistic effect of gold quantum dots (AuQDs) and localized surface plasmons, obtained by blending a AuQD layer and plasmonic gold nanoparticles (AuNPs) in a hole-transport layer (HTL). Different AuQDs emitting blue, green, and red fluorescence were examined in this study. The OSCs were demonstrated to comprise an ITO-coated glass substrate/AuQDs/PEDOT:PSS:AuNPs/P3HT:PCBM/Al structure. The UV-visible spectra, current density versus voltage characteristics, impedance spectra, and incident photon-to-current efficiency of the fabricated devices were evaluated. The results showed an enhancement of photovoltaic efficiency achieved as a result of the increase in short-circuit current density (J _sc) and power conversion efficiency (PCE) in comparison with those of the reference OSCs. The best synergistic effect was found with OSCs consisting of a green-emitting AuQD layer and a HTL containing AuNPs, resulting in the highest improvement in PCE of 13.0%. This indicated that the increase in light harvesting in the developed devices was induced by extended light absorption in the UV region resulting from absorption by the AuQD layer and emission of visible fluorescence from the AuQD layer to the photoactive layers. Moreover, the localized surface plasmon effect of AuNPs, which also contributed to an increase in light trapping in the proposed OSCs, was enhanced by the effect of the AuQDs.

Recent Developments in Graphene/Polymer Nanocomposites for Application in Polymer Solar Cells

Graphene (G) and its derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) have enormous potential for energy applications owing to their 2D structure, large specific surface area, high electrical and thermal conductivity, optical transparency, and huge mechanical strength combined with inherent flexibility. The combination of G-based materials with polymers leads to new nanocomposites with enhanced structural and functional properties due to synergistic effects. This review briefly summarizes recent progress in the development of G/polymer nanocomposites for use in polymer solar cells (PSCs). These nanocomposites have been explored as transparent conducting electrodes (TCEs), active layers (ALs) and interfacial layers (IFLs) of PSCs. Photovoltaic parameters, such as the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF) and power-conversion efficiency (PCE) are compared for different device structures. Finally, future perspectives are discussed.

Exploring the Optical and Morphological Properties of Ag and Ag/TiO₂ Nanocomposites Grown by Supersonic Cluster Beam Deposition

Nanocomposite systems and nanoparticle (NP) films are crucial for many applications and research fields. The structure-properties correlation raises complex questions due to the collective structure of these systems, often granular and porous, a crucial factor impacting their effectiveness and performance. In this framework, we investigate the optical and morphological properties of Ag nanoparticles (NPs) films and of Ag NPs/TiO₂ porous matrix films, one-step grown by supersonic cluster beam deposition. Morphology and structure of the Ag NPs film and of the Ag/TiO₂ (Ag/Ti 50-50) nanocomposite are related to the optical properties of the film employing spectroscopic ellipsometry (SE). We employ a simple Bruggeman effective medium approximation model, corrected by finite size effects of the nano-objects in the film structure to gather information on the structure and morphology of the nanocomposites, in particular porosity and average NPs size for the Ag/TiO₂ NP film. Our results suggest that SE is a simple, quick and effective method to measure porosity of nanoscale films and systems, where standard methods for measuring pore sizes might not be applicable.

A Chiral-Nanoassemblies-Enabled Strategy for Simultaneously Profiling Surface Glycoprotein and MicroRNA in Living Cells

Assemblies of nanomaterials for biological applications in living cells have attracted much attention. Herein, graphene oxide (GO)-gold nanoparticle (Au NP) assemblies are driven by a splint DNA strand, which is designed with two regions at both ends that are complementary with the DNA sequence anchored on the surface of the GO and the Au NPs. In the presence of microRNA (miR)-21 and epithelial cell-adhesion molecule (EpCAM), the hybridization of miR-21 with a molecular probe leads to the separation of 6-fluorescein-phosphoramidite-modified Au NPs from GO, resulting in a decrease in the Raman signal, while EpCAM recognition reduces circular dichroism (CD) signals. The CD signals reverse from negative in original assemblies into positive when reacted with cells, which correlates with two enantiomer geometries. The EpCAM detection has a good linear range of 8.47-74.78 pg mL^-1 and a limit of detection (LOD) of 3.63 pg mL^-1 , whereas miR-21 detection displays an outstanding linear range of 0.07-13.68 amol ng^-1_RNA and LOD of 0.03 amol ng^-1_RNA . All the results are in good agreement with those of the Raman and confocal bioimaging. The strategy opens up an avenue to allow the highly accurate and reliable diagnosis (dual targets) of clinic diseases.

Design and development of plasmonic nanostructured electrodes for ITO-free organic photovoltaic cells on rigid and highly flexible substrates

Indium tin oxide (ITO) is the most common transparent electrode used in organic photovoltaics (OPVs), yet limited indium reserves and poor mechanical properties make it non-ideal for large-scale OPV production. To replace ITO, we designed, fabricated, and deployed plasmonic nanostructured electrodes in inverted OPV devices. We found that active layer absorption is significantly impacted by ZnO thickness which affects the optical field distribution inside the resonant cavity formed between the plasmonic nanostructured electrode and top electrode. High quality Cr/Au nanostructured electrodes were fabricated by nanoimprint lithography and deployed in ITO-free inverted devices on glass. Devices with thinner ZnO showed a PCE as high as 5.70% and higher J _SC's than devices on thicker ZnO, in agreement with finite-difference time-domain simulations. In addition, as the active layer was made optically thin, ITO-based devices showed diminished J _SC while the resonant cavity effect from plasmonic nanostructured electrodes retained J _SC. Preliminary ITO-free, flexible devices on PET showed a PCE of 1.82% and those fabricated on ultrathin and conformable Parylene substrates yielded an initial PCE over 1%. The plasmonic electrodes and device designs in this work show promise for developing highly functioning conformable devices that can be applied to numerous needs for lightweight, ubiquitous power generation.

Photoexfoliation of two-dimensional materials through continuous UV irradiation

This paper describes the preparation of fluorinated graphene nanosheets (FGNs) through photoexfoliation of fluorinated graphite (FG) in the liquid phase. We discovered that UV irradiation of FG dispersions in N-methyl-2-pyrolidone facilitated exfoliation to give FGNs. Transmission electron microscopy and atomic force microscopy revealed that the average thickness of the FGNs was approximately 3 nm; they were considerably thinner than the nanosheets prepared using a conventional sonication approach. Furthermore, when the FGNs were deposited uniformly onto substrates (through spin coating), they formed effective cathode interlayers for polymer solar cells (PSCs), the efficiency of which was 60% greater than that of PSCs containing FGNs prepared through ultrasonication.

Graphene and its derivatives as versatile templates for materials synthesis and functional applications

The obvious incongruity between the increasing depletion of fossil fuel and the finite amount of resources has motivated us to seek means to maintain sustainability in our society. Developing renewable and highly efficient energy conversion and storage systems represents one of the most promising and viable methods. Although the efficiency of energy conversion and storage devices depends on various factors, their overall performances strongly rely on the structure and functional properties of materials. Graphene and its derivatives as versatile templates for materials synthesis have garnered widespread interest because of their flexible capability to tune the morphology and structure of functional materials. Herein, we have demonstrated recent progress on graphene and its derivatives as versatile templates for materials synthesis, particularly highlighting the basic fundamental roles of graphene in the materials preparation process. Then, a concise overview of the functional applications of materials obtained from graphene-templated approaches has been presented with a few selected examples to show the wide scope of potential in energy storage and conversion. Finally, a brief perspective and potential future challenges in this burgeoning research area have been discussed.

Plasmonic Solar Cells: From Rational Design to Mechanism Overview

Plasmonic effects have been proposed as a solution to overcome the limited light absorption in thin-film photovoltaic devices, and various types of plasmonic solar cells have been developed. This review provides a comprehensive overview of the state-of-the-art progress on the design and fabrication of plasmonic solar cells and their enhancement mechanism. The working principle is first addressed in terms of the combined effects of plasmon decay, scattering, near-field enhancement, and plasmonic energy transfer, including direct hot electron transfer and resonant energy transfer. Then, we summarize recent developments for various types of plasmonic solar cells based on silicon, dye-sensitized, organic photovoltaic, and other types of solar cells, including quantum dot and perovskite variants. We also address several issues regarding the limitations of plasmonic nanostructures, including their electrical, chemical, and physical stability, charge recombination, narrowband absorption, and high cost. Next, we propose a few potentially useful approaches that can improve the performance of plasmonic cells, such as the inclusion of graphene plasmonics, plasmon-upconversion coupling, and coupling between fluorescence resonance energy transfer and plasmon resonance energy transfer. This review is concluded with remarks on future prospects for plasmonic solar cell use.

Cross-Linkable Hole-Transport Materials Improve the Device Performance of Perovskite Light-Emitting Diodes

Hybrid organic/inorganic perovskites are promising candidate materials for use in photovoltaic applications. More recently, they have also become highly attractive as active materials for other optoelectronic devices, including lasers, light-emitting diodes, and photodetectors. Nevertheless, difficulties in forming continuous and uniform films and the existence of a charge-injection barrier between the perovskite layer and the electrodes have hindered the development of high-performance perovskite light-emitting diodes (PeLEDs). In this study, a cross-linked hole-transport layer (HTL) is introduced to improve the hole-injection efficiency of PeLEDs. Furthermore, this layer simultaneously facilitates the formation of smooth perovskite layers, presumably because of the different surface energies. More interestingly, the HTL also exhibits strong solvent effects on the device performance. When the processing solvent for fabricating the HTLs is changed from chlorobenzene to N,N-dimethylformamide (DMF), the perovskite layer becomes more uniform and continuous, leading to better surface coverage and higher device efficiency, presumably because DMF has strong affinity toward the perovskite precursors. The approach presented herein could become a general method for decreasing the hole-injection barrier of PeLEDs and, eventually, lead to higher device performance.

Surface plasmon resonance of silver and gold nanoparticles in the proximity of graphene studied using the discrete dipole approximation method

The integration of silver and gold nanoparticles with graphene is frequently sought for the realization of hybrid materials with superior optical, photoelectric and photocatalytic performances. A crucial aspect for these applications is how the surface plasmon resonance of metal nanoparticles is modified after assembly with graphene. Here, we used the discrete dipole approximation method to study the surface plasmon resonance of silver and gold nanoparticles in the proximity of a graphene flake or embedded in graphene structures. Surface plasmon resonance modifications were investigated for various shapes of metal nanoparticles and for different morphologies of the nanoparticle-graphene nanohybrids, in a step-by-step approach. Calculations show that the surface plasmon resonance of Ag nanoparticles is quenched in nanohybrids, whereas either surface plasmon quenching or enhancement can be obtained with Au nanoparticles, depending on the configuration adopted. However, graphene effects on the surface plasmon resonance are rapidly lost already at a distance of the order of 5 nm. These results provide useful indications for characterization and monitoring the synthesis of hybrid nanostructures, as well as for the development of hybrid metal nanoparticle/graphene nanomaterials with desired optical properties.

Improved Device Performance of Polymer Solar Cells by Using a Thin Light-harvesting-Complex Modified ZnO Film as the Cathode Interlayer

In this study, a high-performance inverted polymer solar cell (PSC) has been fabricated by incorporating a zinc oxide (ZnO)/light-harvesting complex II (LHCII) stacked structure as the cathode interlayer. The LHCII not only smoothens the film surface of ZnO, improves the contact between ZnO and the photoactive layer, but also suppresses the charge carrier recombination at the interface, hence all the device parameters of PTB7-based solar cells are simultaneously improved, yielding higher power conversion efficiency (PCE) up to 9.01% compared with the control one (PCE 8.01%). And the thin LHCII modification layer also presents similar positive effects in the PTB7-Th:PC71BM system (PCE from 8.31% to 9.60%). These results put forward a facile approach to the interfacial modification in high-performance PSCs and provide new insight into developing and utilizing inexpensive and environmentally friendly materials from the fields of biological photosynthesis.

Surface Plasmon Resonance Enhanced Polymer Solar Cells by Thermally Evaporating Au into Buffer Layer

Generally, the surface plasmon resonance (SPR) effect of metal nanoparticles is widely applied on polymer solar cells (PSCs) to improve device performance by doping method into solution. Herein, a diameter-controlled thermally evaporation method was used to realize Au nanoparticles (Au NPs) doping into WO3 anode buffer layer in inverted PSCs. The surface energy differences between Au and WO3 inevitably lead to Au growing up through the process from nucleation, isolated island, aggregation of metal islands to continuous films along with the process of evaporation. The atom force microscopy (AFM) images indicate that critical thickness of Au film formation is 8 nm, which is in accordance with current density-voltage (J-V) and incident photon-to-electron conversion efficiency (IPCE) measurement results of optimal device performance. The power conversion efficiency (PCE) with 8 nm Au is dramatically improved from 4.67 ± 0.13% to 6.63 ± 0.17% compared to the one without Au. Moreover, the optical absorption enhancement is demonstrated by steady state photoluminescence (PL), which agrees well with transmission spectrum. The optical and electrical improvement all suggest that thermal evaporation is the appropriate method to further enhance device performance.

Metal Nanoparticle-Decorated Two-Dimensional Molybdenum Sulfide for Plasmonic-Enhanced Polymer Photovoltaic Devices

Atomically thin two-dimensional (2D) transition metal dichalcogenides have also attracted immense interest because they exhibit appealing electronic, optical and mechanical properties. In this work, we prepared gold nanoparticle-decorated molybdenum sulfide (AuNP@MoS₂) through a simple spontaneous redox reaction. Transmission electron microscopy, UV-Vis spectroscopy, and Raman spectroscopy were used to characterize the properties of the AuNP@MoS₂ nanomaterials. Then we employed such nanocomposites as the cathode buffer layers of organic photovoltaic devices (OPVs) to trigger surface plasmonic resonance, leading to noticeable enhancements in overall device efficiencies. We attribute the primary origin of the improvement in device performance to local field enhancement induced by the effects of localized surface plasmonic resonance. Our results suggest that the metal nanoparticle-decorated two-dimensional materials appear to have great potential for use in high-performance OPVs.