All thermal-evaporated surface plasmon enhanced organic solar cells by Au nanoparticles

Au nanoparticles (NPs) are fabricated on indium-tin-oxide substrates by a thermal evaporation method and incorporated to an efficient small molecule organic solar cell (OSC). This renders an all thermal evaporated surface plasmon enhanced OSC. The optimized device shows a power conversion efficiency of 3.40%, which is 14% higher than that of the reference device without Au NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au NPs and the increased conductivity of the device.     

Cooperative plasmon enhanced organic solar cells with thermal coevaporated Au and Ag nanoparticles

Cooperative plasmon enhanced small molecule organic solar cells are demonstrated based on thermal coevaporated Au and Ag nanoparticles (NPs). The optimized device with an appropriate molar ratio of Au:Ag NPs shows a power conversion efficiency of 3.32%, which is 22.5% higher than that of the reference device without any NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au:Ag NPs and the increased conductivity of the device. Besides, factors that determining the performance of the Au:Ag NPs cooperative plasmon enhance organic solar cells are investigated, and it finds that the thickness of MoO₃ buffer layer plays a crucial role. Owing to the different diameter of the thermal evaporated Au and Ag NPs, a suitable MoO₃ buffer layer is required to afford a large electromagnetic enhancement and to avoid significant exciton quenching by the NPs.     

The dual localized surface plasmonic effects of gold nanodots and gold nanoparticles enhance the performance of bulk heterojunction polymer solar cells

In this study, we investigated the effects of plasmonic resonances induced by gold nanodots (Au NDs), thermally deposited on the active layer, and octahedral gold nanoparticles (Au NPs), incorporated within the hole transport layer, on the performance of bulk heterojunction polymer solar cells (PSCs) based on poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C₆₁butyric acid methyl ester (PC₆₁BM). Thermal deposition of 5.3-nm Au NDs between the active layer and the cathode in a P3HT:PC₆₁BM device resulted in the power conversion efficiency (PCE) of 4.6%—that is 15% greater than that (4.0%) for the P3HT:PC₆₁BM device without Au NDs. The Au NDs provided near-field enhancement through excitation of the localized surface plasmon resonance (LSPR), thereby enhancing the degree of light absorption.     

金属表面等离激元增强聚合物太阳电池

研究了Au纳米颗粒表面等离激元增强聚噻吩(P3HT)与富勒烯衍生物(PCBM)共混体系聚合物太阳电池的光电转换效率。Au纳米颗粒表面由双十烷基二甲基溴化铵(DDAB)修饰,能够均匀分散在活性层中。研究了Au纳米颗粒的质量分数对电池性能的影响,发现质量分数为1.2%时,电池性能最佳,转换效率高达3.76%,较未掺杂的参比电池相对提高约20%。掺入Au纳米颗粒后P3HT和PCBM共混膜光吸收显著增强,从而使电池外量子效率大大增加。电池效率的提升主要归结于Au纳米颗粒表面等离激元激发所引起的近场增强。     

Plasmonic Au nanoparticles for enhanced broadband light absorption in inverted organic photovoltaic devices by plasma assisted physical vapour deposition

We use a low vacuum plasma assisted physical vapour deposition (PAPVD) method to deposit a Au nanoparticles (NPs) thin film onto the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer in inverted poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM) organic photovoltaic (OPV) devices. The Au NPs that incorporated into the PEDOT:PSS layer and reached to the active P3HT:PCBM layer can provide significant plasmonic broadband light absorption enhancement to the active layer. An approximately 50–90% improvement in short-circuit current density and in power convention efficiency has been achieved compared with those OPV devices without the plasmonic light absorption enhancement. This technique can be adopted and easily fit into most OPV device fabrication processes without changing other layers’ processing methods, morphologies, and properties.     

Thermo-optical Responses of Nanoparticles: Melting of Ice and Nanocalorimetry Approach

The thermo-optical properties of gold nanoparticles (NPs) embedded in an ice matrix were investigated using photoluminescence and Raman spectroscopy. An intense laser beam alone will not melt ice, but the addition of embedded Au NPs allows for melting with resonant laser light of relatively weak intensity. This is due to the strong absorption of Au NPs in the plasmon resonance regimen. We can determine the threshold melting power, P _melting(T), where T is the background temperature by recording time-resolved Raman scattering signals of the system. A resultant loss of ice signal indicates melting and an absence of conversion to water implicates an irreversible loss of water molecules to the gas phase due to the location of the Au NP agglomerate at or near the ice/vapor surface. For fully embedded NP agglomerates, the ice/water phase transition can be monitored through Raman spectroscopy and the number of NPs in an agglomerate and their interactions can have a greater effect on localized heat generation. The local temperature inside and around the NP agglomerate depends strongly on its geometry and leads to a large scatter in the measured P _melting as a function of the reduced temperature for different agglomerates. Immobilized Au NP agglomerates can also be characterized using single-particle spectroscopy, and results show that the plasmon emission of Au NPs scales with the number of NPs in an agglomerate.     

Broad-band plasmonic Cu-Au bimetallic nanoparticles for organic bulk heterojunction solar cells

In this work, a facile preparation of Cu-Au bimetallic nanoparticles (NPs) with core-shell nanostructures is reported. Importantly, as-prepared Cu-Au NPs are highly stable, solution-processable and exhibit a broad localized surface plasmon resonance (LSPR) band at long wavelengths of 550–850 nm. Highly efficient plasmonic organic solar cells (OSCs) were fabricated by embedding Cu-Au NPs in an anodic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. The average power conversion efficiency (PCE) was enhanced from 3.21% to 3.63% for poly(3-hexylthiophene) (P3HT):phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) based devices, from 6.51% to 7.13% for poly[(ethylhexyl-thiophenyl)-benzodithiophene -(ethylhexyl)-thienothiophene](PTB7-th):PC₆₁BM based devices and from 7.53% to 8.48% for PTB7-th:PC₇₁BM based devices, corresponding to 9.5–13.4% PCE improvement. Such an improvement is very comparable to that (12.5%) obtained in those with plasmonic Au NPs but achieved at lower cost. This study thus demonstrates a novel and cost-effective approach to enhance the photovoltaic performance of OSCs, in combination with the broad-band plasmonic Cu-Au bimetallic nanostructures.     

Supported Faceted Gold Nanoparticles with Tunable Surface Plasmon Resonance for NIR‐SERS

A novel dry plasma methodology for fabricating directly stabilized substrate‐supported gold nanoparticle (NP) ensembles for near infrared surface enhanced Raman scattering (NIR SERS) is presented. This maskless stepwise growth exploits Au‐sulfide seeds by plasma sulfidization of gold nuclei to produce highly faceted Au NPs with a multiple plasmon resonance that can be tuned from the visible to the near infrared, down to 1400 nm. The role of Au sulfidization in modifying the dynamics of Au NPs and of the corresponding plasmon resonance is discussed. The tunability of the plasmon resonance in a broad range is shown and the effectiveness as substrates for NIR SERS is demonstrated. The SERS response is investigated by using different laser sources operating both in the visible and in the NIR. SERS mapping of the SERS enhancement factor is carried out in order to evaluate their effectiveness, stability, and reproducibility as NIR SERS substrates, also in comparison with gold NPs fabricated by conventional sputtering and with the state‐of‐the‐art in the current literature.     

Incorporation of silver and gold nanostructures for performance improvement in P3HT: PCBM inverted solar cell with rGO/ZnO nanocomposite as an electron transport layer

Inefficient light absorption and inefficient charge separation are considered as two major impediments for the efficiency improvement in bulk heterojunction organic solar cells (BHJ OSCs). In this work, we report the simultaneous role of modified electron transport layer (ETL) and photoactive layers on the performance of poly (3-hexylthiophene), [6, 6]-phenyl C61-butyric acid methyl ester (P3HT: PCBM) BHJ OSCs. To modify the ETL, composite of reduced graphene oxide (rGO) (0.4 wt %) and ZnO nanoparticles (NPs) was used, which resulted in efficiency enhancement from 3.13 to 3.81%, as compared to a value of 3.13% when only ZnO was used. Thereafter, to improve upon the optical absorption properties, the photoactive layer is modified by embedding nanoparticles and nanorods of Ag and Au into it. The size of Ag and Au nanoparticles were chosen to be 50 nm while the dimensions of Ag and Au nanorods were so controlled to obtain length of approx. 50 nm and width of ∼10 nm. All the devices were fabricated in inverted geometry and 20 wt% nanostructures embedded devices showed the best results. For Ag and Au NPs embedded devices, the maximum power conversion efficiency was found to be 4.21% and 4.44%, respectively. On the other hand, for Ag and Au NRs embedded devices, the maximum efficiency was 4.37% and 4.85%, respectively. For comparison, the control devices where no nanostructures were embedded, which shows efficiency of 3.81%. Therefore, an overall enhancement in efficiency was nearly 1.21 and 1.1, 1.16, 1.14, 1.27 fold after modifying ETL as well as the active layer. The reasons for performance improvement were ascribed to better charge extraction properties of ETL, enhanced light absorption due to localized surface plasmon resonance (LSPR) and efficient light scattering by the nanostructures and improved global mobilities.     

Surface plasmon spectroscopy of thin composite films of Au nanoparticles and PEDOT:PSS conjugated polymer

We studied the effect of Au nanoparticles (NPs) on optical properties of composite films of poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) mixed with Au NPs of 20, 40 and 60 nm in diameter by surface plasmon resonance (SPR) spectroscopy. The excitation wavelength of SPR redshifts with increasing the concentration of Au NPs in the Au/PEDOT:PSS composite films. The SPR spectra were simulated by using transfer matrix method (TMM) and effective medium approximation (EMA). The SPR wavelength redshift was ascribed to the film thickness increase of Au/PEDOT:PSS composites rather than effective permittivity variation of the composite films induced with Au NPs inclusion.     

Large AuAg Alloy Nanoparticles Synthesized in Organic Media Using a One‐Pot Reaction: Their Applications for High‐Performance Bulk Heterojunction Solar Cells

A one‐pot synthesis of large size and high quality AuAg alloy nanoparticles (NPs) with well controlled compositions via hot organic media is demonstrated. Amid the synthesis, complexation between trioctylphosphine (TOP) and metal precursors is found, which slows down the rate of nucleation and leads to the growth of large‐size AuAg nanoalloys. The wavelength and relative intensities of the resulting plasmon bands are readily fine‐tuned during the synthetic process using different Au/Ag precursors molar ratios. In the polymer solar cells, a key step in achieving high efficiency is the utilization of 1% Au₁₁Ag₈₉ alloy NPs embedded in the active layer to promote the power conversion efficiency (PCE) up to 4.73%, which outperforms the reference device based on the control standard device of poly(3‐hexylthiophene) (P3HT):phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) under identical conditions. Corresponding increases in short‐circuit current density (J_sc), open‐circuit voltage (V_oc), fill factor (FF), and incident photon‐to‐current efficiency (IPCE) enable 31% PCE improvement due to the enhancement of the light‐trapping and the improvement of charge transport in the active layer. The findings advance the fundamental understanding and point to the superiority of Au₁₁Ag₈₉ nanoalloys as a promising metallic additive over Au, Ag, and Au₂₈Ag₇₂ alloy NPs to boost the solar cell performance.     

Enhancement of the power conversion efficiency due to the plasmonic resonant effect of Au nanoparticles in ZnO nanoripples

Au-ZnO nanoripples (NRs) were synthesized by using a sol-gel method for utilization as an electron transport layer (ETL) in inverted organic photovoltaic (OPV) cells. Absorption spectra showed that the plasmonic broadband light absorption of the ZnO NRs was increased due to the embedded Au nanoparticles (NPs). In particular, as compared to regular inverted OPV cells with a ZnO NR ETL, the incident photon-to-current efficiency of the inverted OPV cells with a Au-ZnO NR ETL was significantly enhanced due to the localized surface plasmon resonance (LSPR) effect of the Au NRs. The enhancement of the short-circuit current density (10.05 mA/cm²) of the inverted OPV cells with a Au-ZnO NR ETL was achieved by the insertion of the Au NPs into the ZnO NRs. The power conversion efficiency (PCE) of the OPV cells with Au-ZnO NRs was 3.25%. The PCE of the inverted OPV cells fabricated with a Au-ZnO NR ETL was significantly improved by 20.37% in comparison with that of inverted OPV cells fabricated with a ZnO NR ETL. This improvement can mainly be attributed to an increase in light absorption in the active layer due to the generation of the LSPR effect resulting from the existence of the Au NPs embedded in the ZnO NRs.     

Realizing both improved luminance and stability in organic light-emitting devices based on a solution-processed inter-layer composed of MoOX and Au nanoparticles mixture

We report on the solution-processed mixture of Au nanoparticles (NPs) and MoO_X as an inter-layer in organic light-emitting devices (OLEDs), leading to the enhanced light emission and good stability. An impressive enhancement in current efficiency and power efficiency is achieved up to 70% and 100%, respectively. A systematic study to the effect of the Au NPs:MoO_X inter-layer on OLEDs demonstrates that the improved electrical properties is mainly ascribed to the enhanced hole injection due to the high work function of MoO_X and the good conductivity of Au NPs, and the enhanced optical properties is mainly attributed to the localized surface plasmon induced by Au NPs, which makes a great contribution to the improved efficiency. Besides, Au NPs:MoO_X inter-layer also behaves superior to the frequently-used polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) in device stability. The decay ratio for Au NPs:MoO_X based device is 60% after 80 h, while it is nearly dying out for the device with PEDOT:PSS inter-layer.     

TiN Nanoparticles for Enhanced THz Generation in TDS Systems

By virtue of the surface plasmon resonance effect, plasmonic nanoparticles (NPs) can localize the light field and significantly enhance the performance of some optoelectronic devices. In this work, NPs are employed for an enhanced generation of terahertz radiation from LT-GaAs-based antennas. Therefore, we have prepared plasmonic TiN NPs by direct ultrasonication (ULS) and pulsed laser ablation (PLA) techniques. The zeta potential, particle size, and absorbance were used to characterize the NPs in their colloidal forms in a comparison to commercial Au NPs. A layer of polydispersed titanium nitride (TiN) NPs prepared by PLA and deposited on the surface of an LT-GaAs device shows a significant improvement of terahertz signal generation from these devices with an enhancement of the peak to peak amplitude of 100%.     

Evolution of Anisotropic Arrow Nanostructures during Controlled Overgrowth

Anisotropic metal nanoparticles (NPs), such as high-aspect-ratio Au nanorods (NRs), play an important role for applications in photocatalysis, sensing, and drug delivery because of their adjustable plasmon resonances. Their performance for these applications can be further improved by fine-tuning their morphologies. Achieving desired NP architectures requires insight into their formation mechanisms. Here, liquid-phase transmission electron microscopy is used to directly follow the overgrowth of Au NR seeds into nanoarrows (NAs) with fourfold symmetric wings along the sides. Adding thiol molecules like L-cysteine to the growth solution can lead to the formation of NAs with periodic prismatic teeth instead of the straight side wings. These observations suggest that this transition is controlled by binding of L-cysteine to the NR surface, which in turn, slows down the metal deposition rate, switching the overgrowth from the kinetically to thermodynamically controlled process. Furthermore, simulations demonstrate that these prismatic teeth enhance the NPs’ plasmonic properties. The study describes how thiol additives control the morphological evolution of metal NPs, which is important for the fabrication of NPs with tailored shapes for a broad range of applications.     

Antireflective Nanoparticle Arrays Enhance the Efficiency of Silicon Solar Cells

In this study, the phenomenon of light trapping in Si solar cells coated with metal (Au) and dielectric (TiO₂, SiO₂) nanoparticles (NPs) is systematically investigated. In contrast to previous reports, herein it is proposed that the photocurrent enhancement of solar cells should be attributed to the limited antireflection ability of the Au NP arrays. In other words, the Au NP arrays might not enhance the absorption of the active layer in cells when no light is reflected from the air–substrate interface. Therefore, the Au NPs are replaced with dielectric NPs, which possess lower extinction coefficients, and then the antireflection property of the TiO₂ NP arrays is optimized. A simple, rapid, and cheap solution‐based method is used to prepare close‐packed TiO₂ NP films on Si solar cells; these devices exhibit a uniform and remarkable increase (ca. 30%) in their photocurrents. To the best of the authors’ knowledge, this uniform photocurrent enhancement is greater than those obtained from previously reported metal and dielectric NP–enhanced Si wafer‐based solar cells.     

Blue Electroluminescence Enhancement of Poly{2,7‐(9,9′‐dioctylfluorene)‐co‐4‐diphenylamino‐4′‐bipenylmethylsulfide} Incorporating Side‐Chain‐Tethered Gold Nanoparticles

Through in situ reduction of a gold precursor, we have tethered gold nanoparticles (Au NPs) to the side chains of poly{2,7‐(9,9′‐dioctylfluorene)‐co‐4‐diphenylamino‐4′‐bipenylmethylsulfide} (PF‐DBMS) through its ArSCH₃ anchor groups. The presence of 1 wt % of the tethered Au NPs led to a reduction in the degree of aggregation of the polymer chains, resulting in a 50 % increase in its quantum yield. The electroluminescence of a 1 wt % Au/PF‐DBMS device was almost four times higher in terms of its maximum brightness and its full‐width‐at‐half‐maximum emission peak was much narrower than that of a pure PF‐DBMS device; the presence of a small amount of Au NPs significantly enhances the electron injection and transport and suppresses the photo‐oxidation of PF‐DBMS.     

Enhanced carrier mobility and photon-harvesting property by introducing Au nano-particles in bulk heterojunction photovoltaic cells

In this study, polymer solar cells (PSCs) doped with Au nanoparticles (Au NPs) were successfully fabricated to maximize the photon-harvesting properties on the photoactive layer. In addition, a conductivity-enhanced hybrid buffer layer was introduced to improve the photon absorption properties and effectively separate the generated charges by adding Au NPs and dimethylsulfoxide (DMSO) to the PH 500 as a buffer layer. The PSC performance was optimized with a 88% improvement over the conventional PSCs (photoactive area: 225 mm², power conversion efficiency (PCE): 3.2%) by the introduction to the buffer layer of Au NPs and DMSO at 10 wt% and 1.0 wt%, respectively, and with 15 wt% Au NP doping in the photoactive layer. The internal resistance was decreased due to the increased photocurrent caused by the localized surface plasmon resonance (LSPR) effect of the Au NPs in the photoactive layer and by the improvement of carrier mobility induced by the DMSO doping of the buffer layer. As a result, the series resistance (R_S) deceased from 42.3 to 19.7 Ω cm² while the shunt resistance (R_SH) increased from 339 to 487 Ω cm².     

The application of porous Si photonic crystals for metal-resonance enhanced fluorescence

This paper has demonstrated the resonance fluorescence enhancement of R6G when gold nanoparticles (Au NPs) deposited in the porous Si photonic crystal device. Both of microcavity (MC) and distributed Bragg reflector (DBR) with different parameters are investigated for making the photon transmission of photonic crystal device play an optimal role in enhancing fluorescence resonance. While minor changes were observed on the DBR substrates, a significant change in the intensity of enhanced fluorescence varies with the defect modes of MC substrates. Particularly, the strongest enhancement has been presented as the MC defect mode wavelength located at the maximum absorption wavelength of Au NPs. In this case, the fluorescence intensity of R6G on MC device is 2.5 times of that of R6G based on DBR device.     

Solution-based nanostructure to reduce waveguide and surface plasmon losses in organic light-emitting diodes

Organic light-emitting diodes (OLEDs) typically have low out-coupling efficiency. In this paper, a solution-based nanoparticle layer is presented as a nanostructure to enhance the out-coupling efficiency of OLEDs. Silica nanoparticles (NPs) are randomly distributed on indium tin oxide by spin-coating a silica NP solution. By further spin-coating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as a hole injection layer, a randomly corrugated PEDOT:PSS layer is fabricated. A nanostructured OLED having the corrugated PEDOT:PSS layer above the NP layer shows enhanced external quantum efficiency and power efficiency because the trapped light of the waveguide and surface plasmon modes is extracted by Bragg diffraction. The nanostructured OLED shows no angular dependence due to the broad periodicities of the corrugation. The simply fabricated and cost-effective silica NP layer nanostructure, which does not require a lithography step, has potential to enhance the efficiency of both white OLED displays and lighting.