Tailoring the inherent optical responses of pi-conjugated organic semiconducting materials by integrating them with plasmonic entities has garnered substantial research attention. Herein, we demonstrated a superior optical nonlinearity of nanoribbons of N,N '-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) integrated with Au nanoparticles (NPs) using an open aperture Z-scan measurement with a Q-switched Nd:YAG laser of wavelength 532 nm and pulse width 7 ns. These integrated one-dimensional nanohybrid systems exhibited an effective nonlinear absorption (NLA) coefficient, beta eff of 74 cm/GW at an on-axis input intensity, I 0 = 0.27 GW/cm2, which is 3.08 and 1.35 times higher than those of the bulk PTCDI-C8 (monomers) and their pristine nanoribbons, respectively. The enhanced nonlinear optical activity was attributed to the exhibition of strong reverse saturable absorption (RSA) that results from the synergistic effects of inherent plasmonic oscillations of Au NPs (470-580 nm) and the characteristic excitonic transition of PTCDI-C8 nanoribbons (506-536 nm). Theoretical studies carried out using the finite-difference time-domain (FDTD) simulations on different models of Au-PTCDI-C8 nanohybrids revealed the strong coupling of an induced plasmonic hotspot around the Au NPs with PTCDI-C8 nanoribbons. Around 60 times enhancement in E-field intensity in the vicinity of Au NPs was theoretically monitored on integrated PTCDI-C8 nanoribbons, which is believed to be responsible for their enhanced nonlinear optical responses. Furthermore, these nanohybrids exhibited a limiting threshold of 1.75 J/cm2, comparable to or better than that of recently reported pi-conjugated and nanohybrid materials, highlighting the efficacy of this approach in developing optical nanomaterials with exceptional nonlinear absorption characteristics.

Au and Ag are the most prominent plasmonic materials to study Surface-Enhanced Raman Spectroscopy (SERS) because of their wide tuning of localized surface plasmon resonance in the broad wavelength range. In the present work, the formation of nanostructures of Au single-layer, Au/Ag bi-layer, and Au/Ag/Au/Ag four-layer thin films on silicon substrates by low energy Kr++ ion irradiation with fluences of 1 x 1015 and 3 x 1015 ions/ cm2 was systematically studied and were used for the detection of dye molecules. The surface morphology and microstructural analysis indicated the formation of different nanostructures with different ion fluences by atomic force microscopy and field emission scanning electron microscopy. Rutherford backscattering spectrometry results indicate a considerable change in film thickness after ion irradiation, mainly due to the removal of surface atoms due to sputtering. The maximum enhancement in Raman intensity of R6G was observed in the Bi-layer Au-Ag substrate compared to other substrates with an enhancement factor of 4.78 x 106 corresponding to a 1516 cm-1 characteristic peak in SERS analysis. Coumarin 343 molecules trace amount were detected to determine the versatility of the substrate. A finite-difference time-domain simulation was performed to provide a better understanding of the nanostructure hot-spots formation and support the obtained SERS results.

Recent advancements in nanotechnology have led to the development of surface-enhanced Raman spectroscopy (SERS) based rapid and low-cost technologies for ultra-sensitive label-free detection and identification of molecular analytes. Herein, we utilized the synergistic plasmonic and chemical enhancement effects of Au-WS2 nanohybrids to attain the high-intensity Raman signals of targeted analytes. To develop these nanohybrids, a series of monodispersed Au nanoparticles (NPs) of varying diameters from 20 to 80 nm was chemically synthesized and successively blended with liquid-phase exfoliated WS2 nano-flakes of average lateral size 90 nm. They provided a maximum enhancement factor (EF) of ∼1.80 × 109 corresponding to the characteristic peaks at 1364 cm-1 and 1512 cm-1 for R6G analyte molecules. Theoretical studies based on the finite-difference time-domain simulations on Au-WS2 nanohybrid systems revealed a huge field-intensity enhancement with an EF of more than 1000 at the plasmonic hotspots, which was induced by the strong coupling of individual plasmon oscillations of the adjacent Au NPs upon light interactions. These electromagnetic effects along with the chemical enhancement effects of WS2 nanoflakes were found to be mainly responsible for such huge enhancement in Raman signals. Furthermore, these hybrids were successfully employed for achieving highly sensitive detection of the E. coli ATCC 35218 bacterial strain with a concentration of 104 CFU mL-1 in phosphate-buffered saline media, indicating their real capabilities for practical scenarios. The findings of the present study will indeed provide vital information in the development of innovative nanomaterial-based biosensors, that will offer new possibilities for addressing critical public health concerns.

The efficiency of organic solar cells (OSCs) has been improved more than 19% recently with the development of non-fullerene acceptor materials. Further improvement is still attainable with the optimal combinations of do-nors and acceptors that provide minimal energy losses. In this work, a data-enabled machine-learning (ML) framework was employed to predict the energy losses in the polymer:non-fullerene acceptor based devices. Based on the collected experimental dataset, the prediction accuracies of various machine learning models were sys-tematically compared by estimating mean absolute percentage errors (MAPE), root mean squared errors (RMSE), and person's r coefficient. The Random Forest regression model showed the best performance in predicting the energy losses with a correlation coefficient of 0.83 and relative error in the range of 0 - 20%. The predictive ability of this model was further validated using the different parameters of devices with power conversion efficiency range of 6 - 18%. Three different donor-acceptor combinations were chosen for fabricating the photovoltaic devices to fit this model into practical devices and experimentally obtained energy loss values were compared with the predicted values. In addition, the device parameters with the molecular descriptors to un-derstand the correlation and energy loss is highly correlated with the HOMO offset. This study demonstrates that the ML approach provide an effective method to predict and virtual screen of promising donor-acceptor pairs with minimal energy loss and would be useful for developing next-generation high performance solar cell materials.

Recent developments in novel conjugated polymer donor and non-fullerene acceptor (NFA) materials with promising properties have led to an unprecedented increase in the power conversion efficiency (PCE) of organic solar cells (OSCs) by more than 19%. However, in this era of artificial intelligence, identifying highly potential combinations of such donor and acceptor materials using the current trial-and-error experimental approaches is certainly not feasible. Herein, we effectively predicted and screened the performance of OSCs based on various polymer:NFA combinations by employing a data-driven machine learning (ML) approach and successively validated this predictivity by fabricating a set of highly efficient devices with a PCE up to 15.23%. A dataset of 1242 experimentally verified donor : acceptor (D/A) combinations was constructed, and the corresponding material descriptors were generated to train and test five different supervised ML models. Using a unique combination of both frontier molecular orbital (FMO) and RDKit descriptors as input features, the random forest ML model performed best for predicting the PCE with a Pearson's coefficient (r) of 0.791 and a mean absolute percentage error of 2.004. On the other hand, the gradient-boosting ML model showed a substantially improved performance for the prediction of both JSC and VOC with high r values of 0.842 and 0.862, respectively. Furthermore, the importance of critical RDKit descriptors along with FMO descriptors in such performance predictions was realized by SHapley Additive exPlanations (SHAP) analyses. Therefore, the proposed ML framework guided by these new descriptors will indeed be fruitful for designing new molecules and screening and predicting suitable D/A combinations to accelerate the development of highly efficient OSCs. The machine learning approach was employed to explore the relationship between molecular structure and photovoltaic properties using frontier molecular orbital and RDKit descriptors, which enabled us to screen and identify potential donor and acceptor combinations for efficient organic solar cells.

Recently, the power conversion efficiency (PCE) of organic solar cells (OSCs) has significantly progressed with a rapid increase from 10 to 19% due to state-of-the-art research on nonfullerene acceptor molecules and various device processing strategies. However, OSCs still exhibit significant open circuit voltage loss (ΔVOC ∼ 0.6 V) due to high energetic offsets and molecular disorder. In this work, we present a systematic investigation to determine the effects of energetic offset and disorder on different recombination losses in open circuit voltage (VOC) using 13 different photoactive layers, wherein the PCE and ΔVOC vary in the ranges of 2.21-14.74% and 0.561-1.443 V, respectively. The detailed voltage loss analysis of all these devices was carried out, and voltage losses were correlated with energetic offset and disorder. This has enabled us to identify the key features for minimizing the voltage loss like: (1) a low energy offset between the donor and acceptor molecular states is essential to attain a nonradiative voltage loss (ΔVOC, nrad) as low as ∼200 meV and (2) Urbach energy, which is a measure of the materials' disorder and packing, should be low for the minimization of the radiative voltage loss (ΔVOC, rad). In addition, time-resolved photoluminescence spectroscopy was employed to further understand the exciton dynamics of pristine materials and donor-acceptor blends. It was observed that the absorbers with ultralong exciton lifetime (∼1000 ps) produce higher efficiencies. The current study emphasizes the importance of simultaneously testing photovoltaic performance and active layer exciton dynamics for rational device optimization and opens new prospects for designing novel molecules with fine-tuning of energetic offset and disorder with longer exciton lifetime which is the effective strategy to boost the efficiency of OSCs to their modified Shockley-Queisser (SQ) limit by minimizing radiative and nonradiative voltage losses.

The recent use of surface plasmon resonance of metal nanoparticles was shown to be a promising method to achieve more light harnessing in solar photovoltaic (PV) devices. To build on this promise gold nanoparticles (AuNPs) including Au-Pink, Au-Orange, Au-Purple, Au-Blue were synthesized using chemical reduction method, their optical and morphological properties were characterized and they were used in PV devices. The active layer of dye-sensitized solar cells having titanium dioxide (TiO2) solid microsphere (MS) made up of nanoparticles granules were coated with AuNPs. This Au-TiO2 MS hybrid DSSC boosted light harvesting, charge separation, and improved the charge transport resulting in an improvement of both short circuit current and open circuit voltage. The power conversion was boosted 16% compared to the control photoanode of TiO2 solid microsphere. Further enhancement in the short circuit current was observed during the incorporation of both Au and Ag, bimetallic nanoparticles in the TiO2 matrix. An overall photo to electron conversion efficiency of 8.73% was obtained due to the plasmonic cooperation effect of TiO2-Ag-Au hybrid structures, which is 65% increase over pure TiO2 DSSCs. The local electrified intensity enhancement around the individual Ag, Au nanoparticles and plasmonic coupling of the Ag-Au combination have been used to explain these results with finite-difference time-domain simulation.

Although doping has the potential to improve the performance of organic photovoltaic cells (OPVc), doping effects on charge transport, recombination, and energetic disorder are still obscure. Doping has two opposing effects: on the one hand, dopant ions create more trap centers, while free dopant‐induced charges fill deep states, potentially providing better performance. The optimum amount of dopants can considerably improve the performance of OPVc. Herein, the energetic distribution of trap states in P3HT: PC71BM‐based OPVc doped with iron pyrite nanocubes (NCs) is reported. Using the reverse bias transient photocurrent (TPC) measurement, the energetic trap distributions with different doping conditions are studied. The photovoltaic characteristics and TPC phenomena of the OPVc greatly improve through doping. Variations in trap distributions with doping levels are analyzed to interpret the obtained trap density of states profiles. The light‐dependent current–voltage characteristics help to identify the presence of a less trap‐assisted recombination process in the optimum device. This study highlights the mechanism for performance improvement in devices with optimal doping of iron pyrite NCs.

Utilizing plasmonic effects of metal nanostructures on tailoring the properties of semiconducting materials has gained substantial research attention in the past 10 years. Here, we report the plasmon resonance-induced enhanced optical nonlinearity of Au-WS2 nanohybrids prepared via the blending of liquid phase exfoliated few-layer WS2 nanosheets with chemically synthesized spherical gold nanoparticles (NPs). Nonlinear optical properties were studied using the open aperture Z-scan technique with nanosecond laser pulses of wavelength 532 nm, which lie in the plasmonic band of Au NPs (480-550 nm) and B-excitonic transition range of WS2 nanosheets (520-535 nm). Au-WS2 nanohybrids exhibited an enhanced nonlinear absorption and optical limiting activity with an effective nonlinear absorption coefficient of 182 cm/GW at an on-axis input intensity of 0.14 GW/ cm2, which is 3.87 times higher than that of bare WS2 nanosheets. The improved NLO response of nanohybrids is due to the plasmon resonance-induced local field effects, which significantly enhance B-excitonic transitions in WS2 nanosheets. The simulated field intensity enhancement profile also confirmed the effect of formation, where a strong interaction of plasmonic fields with WS2 nanosheets is clearly visible. The enhancement observed in simulated absorption density profiles indicated improved B-excitonic transitions in WS2 nanosheets due to the resonant plasmonic field. Au-WS2 nanohybrids exhibited a low limiting threshold of 0.55 J/cm2, which is better than that of many eminent nanohybrids reported so far. The strategy followed in this work for attaining superior nonlinear optical responses in Au-WS2 nanohybrids will be useful to develop novel nonlinear optical materials for photonic device applications.

Raising the photocurrent and successivelyachieving ahigh powerconversion efficiency (PCE) in organic solar cells (OSCs) with physicallythin photoactive layers is usually a highly challenging task becauseof their excitonic nature. Herein, we utilized the synergistic plasmoniceffects of multi-shaped Au nanostructures (diameter/edge length & SIM;50nm) hybridized with few-layer WS2 nanosheets in improvingthe photocurrent of fullerene and non-fullerene-based OSCs. A PCEenhancement of more than 15% and an external quantum efficiency improvementin a broad wavelength range of 350-700 nm were demonstratedby incorporating these Au-WS2 nanohybrids as an interlayerbetween hole transport and photoactive layers. The PCE enhancementwas mainly due to the improved photocurrent (& SIM;12.41%) via broad-rangeplasmonic effects of Au nanostructures. Finite-difference time-domainsimulations were performed to comprehensively study the plasmonicresponses, such as scattering efficiency, direction-dependent scattering,and near-field effects of individual nanostructures. The effectiveplasmonic range over 350-700 nm and more than 50% forward lightscattering indicated that these hybridized Au nanostructures are highlysuitable candidates to couple the incident light into the active layer.Near-field intensity enhancement and subsequent enhancement in absorptiondensity confirmed the elevated local density of optical states inAu-WS2 nanohybrid-based devices. Therefore, the presentstudy emphasizes the role of hybridized Au-WS2 nanostructuresin improving the light-harvesting capability of OSCs in a broad wavelengthrange, hence attaining a significant improvement in device photocurrent.

Detailed understanding of the various influences of deposition conditions on the structure–property relationship for spray-coated polymer films is crucial for their scalable device applications. In the present study, the influences of in-situ substrate temperature and acoustic substrate vibration on the charge carrier dynamics of poly(3-hexylthiophene) and [6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) based ultrasonic spray-coated polymer solar cells have been investigated thoroughly by employing Impedance spectroscopy, Mott–Schottky analysis, Urbach energy analysis, and trap-state density estimations. The device prepared under the influences of in-situ substrate temperature and acoustic substrate vibration shows more than three times enhancement in PCE (3.24%) compared to that of the reference one (0.9%). A correlation between charge transport behaviour and deposition conditions has been identified for the devices. The surface roughness and rigid droplet boundaries were found to set major performance limitations. The overall resistance of the devices was found to get decreased by 70% whilst the global charge carrier mobility was found to get increased from 6.09 × 10–5 to 9.43 × 10–4 cm2 V−1 s−1 with the simultaneous application of substrate temperature and acoustic vibration, forming uniform and homogeneous films with much reduced surface roughness and droplet boundaries compared to the untreated reference devices. Systematic variation in the trap and defect-state densities were also observed. The trap-state density reduced from 5.03 × 1015 to 2.71 × 1015 cm−3 after the combined treatment of in-situ annealing and substrate vibration. Urbach energy was found to be 218.4 meV for the untreated active layer, which reduced to 177.2 meV for the active layer treated with in-situ-annealing and acoustic substrate vibration. The superior electrical properties achieved by optimizing the active layer morphology using different spray deposition conditions led to around four times enhancement in device efficiency.

Hybrid nanostructures with superior optical and electrical properties have shown great promise in improving the performance of photovoltaic devices. Herein, we report the development of metal-semiconductor hybrid nanostructures via the blending of chemically synthesized Au nanoparticles (NPs) (diameter ~17 nm) and liquid phase exfoliated WS2 nanosheets (lateral size ~ 80 nm). The Zeta potential measurement and the Raman spectroscopy were employed to evaluate the stability and dispersity of synthesized nanostructures. Organic solar cells with reference structure ITO/PEDOT: PSS/active layer/LiF/Al were fabricated by incorporating the hybrid nanostructures at the PEDOT: PSS/active layer interface. A simultaneous rise in short-circuit current density and fill factor was achieved after incorporating the nanostructures, leading to an efficiency enhancement of 20.24% compared to the reference device. The performance enhancement of devices is mainly attributed to the improvement in active layer absorption and charge transport through the PEDOT: PSS layer. Moreover, the role of plasmonic effects on the performance enhancement of devices was investigated by monitoring the electric field intensity distribution around the Au NPs using finite-difference time-domain simulations.

The power conversion efficiency (PCE) of organic solar cells (OSCs) has recently progressed significantly with a rapid increase from 10% to 19% due to state-of-the-art research on non-fullerene acceptor molecules and various device processing strategies. However, OSCs still exhibit significant open circuit energy loss (~0.6 eV) due to disorder and excitonic nature of the organic semiconductors. In this work, we explored the role of energetic disorder on the total energy loss of bulk heterojunction OSCs. For this purpose, different donor-acceptor combinations were used to fabricate the OSCs, and various electrical characterizations were carried out in detail. The approximation of the energetic disorder was measured in term of Urbach energy (E U ) from the band tail of spectra. The correlation between open circuit energy loss due to different recombination processes and Urbach energy were observed. As E U was decreased, the energy loss decreased due to more ordered molecular packing and lower energetic disorder, resulting in better device performance. These finding show the need of reducing the energetic disorder, hence lower energy losses for boosting the PCE of the OSCs.

Dye sensitized solar cells (DSSCs) have numerous advantages, but in order to use widespread industrial deployment we need to boost the power conversion efficiency. One promising approach to improve DSSC performance is to improve the spectral response of sensitizers with metal nanoparticle-based surface plasmon resonance. Even single shaped nanoparticles (NPs), however, have physical limitations. Thus, in this study a simple synthesis route is used to fabricate multishaped silver (Ag) NPs to create a coupled plasmonic effect in DSSC to cover more of the solar spectrum. The impact of multishaped AgNPs combinations are studied to determine which aspects improve the power conversion efficiency of DSSC. A detailed investigation was made of both the TiO2 (XRD) and AgNPs (UV-Vis spectrometry) to couple the impacts on the DSSC (I-V) with the combination of the morphologies (TEM and FESEM) of AgNPs. Synthesized AgNPs with distinct extinction cross section covers the visible and IR regime from 300 nm to 1100 nm by tuning its plasmonics band. It is inferred that multi-shaped AgNPs predominately enhance the light harvesting, charge separation and carrier transportation. The results show that the increment in short circuit current and open circuit voltage resulted in an increase of 45% overall power conversion efficiency in the standard DSSC device is attributed to the usage of multi-shaped AgNPs. Finally, a mechanism is proposed to support the outcome of the experiment by demonstrating the extinction cross section and the local field of the various shaped AgNPs using Finite-difference time-domain (FDTD) simulation. (C) 2021 Elsevier B.V. All rights reserved.

Understanding the linear and nonlinear optical (NLO) responses of two-dimensional nanomaterials is essential to effectively utilize them in various optoelectronic applications. Here, few-layer MoS2 and WS2 nanoflakes with lateral size less than 200 nm were prepared by liquid-phase exfoliation, and their linear and NLO responses were studied simultaneously using experimental measurements and theoretical simulations. Finite-difference time-domain (FDTD) simulations confirmed the redshift in the excitonic transitions when the thickness was increased above 10 nm indicating the layer-number dependent bandgap of nanoflakes. WS2 nanoflakes exhibited around 5 times higher absorption to scattering cross-section ratio than MoS2 nanoflakes at various wavelengths. Open aperture Z scan analysis of both the MoS2 and WS2 nanoflakes using 532 nm nanosecond laser pulses reveals strong nonlinear absorption activity with effective nonlinear absorption coefficient (β eff) of 120 cm GW−1 and 180 cm GW−1, respectively, which was attributed to the combined contributions of ground, singlet excited and triplet excited state absorption. FDTD simulation results also showed the signature of strong absorption density of few layer nanoflakes which may be account for their excellent NLO characteristics. Optical limiting threshold values of MoS2 and WS2 nanoflakes were obtained as ∼1.96 J cm−2 and 0.88 J cm−2, respectively, which are better than many of the reported values. Intensity dependent switching from saturable absorption (SA) to reverse SA was also observed for MoS2 nanoflakes when the laser intensity increased from 0.14 to 0.27 GW cm−2. The present study provides valuable information to improve the selection of two-dimensional nanomaterials for the design of highly efficient linear and nonlinear optoelectronic devices.

Core-shell structure has been getting tremendous research interest due to their tunable multifunctional properties, induced as a result of the co-occurrence of more than one nanostructured phases. Here we report detailed nonlinear optical studies of Au@Ag core-shell nanostructures under ns pulse excitation. The size and shell thickness of the core-shells were obtained from TEM images. A significant blue shift from 519 nm to 411 nm in surface plasmon maxima is observed on forming Ag (shell) layer on Au (core) nanosphere and a slight red shift (411 nm to 425 nm) was observed as the shell thickness increases from 7.5 to 22.5 nm. All the samples exhibited reverse saturable absorption behavior and the extent of optical limiting activity enhanced on increasing the shell thickness. Nonlinear refraction properties of the samples were also analyzed and all the samples were found to be exhibiting negative nonlinearity. Improved optical limiting activity on increasing shell thickness of the studied system could be attributed to enhanced local field effect and nonlinear scattering effect, which is confirmed from the finite difference time domain simulation analysis. The good nonlinear optical properties of Au@Ag core-shell structures ensure its potential for future nonlinear optical applications. (C) 2021 Published by Elsevier B.V.

Multifunctional TiO2 powder consisting of solid microspheres/nanoparticles (NPs) was obtained in single step hydrothermal method. The insights of mesoporous solid TiO2 microspheres are observed as interconnected particles granules in the field emission scanning electron microscope (FESEM) investigation. Secondly, Ag nanoparticles (AgNPs) of spherical shaped with narrow size distribution was synthesised by reduction process and its extinction maximum at 413 nm was observed from UV-Vis analysis. Screen printed TiO2 photoanode containing plasmonic AgNPs was utilised to construct the dye sensitized solar cell (DSSC). The efficiency and optical properties of the bare and plasmonic devices were compared. Noticeable improvement in device efficiency is attributed to plasmonic properties of the incorporated AgNPs. (C) 2020 Elsevier B.V. All rights reserved.

Inverted polymer solar cells (PSCs) based on poly-3-hexylthiophene (P3HT):[6,6]-phenyl C71 butyric acid methyl ester (PCBM) active layer were fabricated. Thin films of zinc oxide (ZnO) and molybdenum trioxide (MoO3) were used as cathode and anode buffer layers, respectively. Optical properties of ZnO thin films were studied by measuring the transmission spectrum. Thickness of MoO3 layer was optimized to achieve the best device performance. Device with 7 nm thick MoO3 layer exhibited a maximum power conversion efficiency of 2.07%.

Achieving high absorption enhancement in a broad wavelength range without increasing the thickness of active layer is essential for improving the performance of polymer solar cells. In this work, we report efficiency enhancement in poly({4,8-bis [(2- ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluom-2-[(2-ethyl-hexyl)carbonyl]thieno [3,4-b]thiophenediyl}): [6,6]-phenyl C-71-butyric acid methyl ester active layer based polymer solar cells by incorporating silver nanostructures simultaneously in cathode buffer layer and active layer. Efficiency of the device was increased from 6.53% to 7.53% after incorporating the nanostructures. The plasmonic devices exhibited superior performance in a broad wavelength range from 450 nm to 750 nm. Photoluminescence measurements were carried out to confirm the improvement in light harvesting capability of the devices. Finite-difference time-domain simulations and Raman spectroscopy were employed to verify the electric field intensity enhancement around the nanostructures. The performance enhancement mechanism was realized based on theoretical simulations and optical measurements.

Plasmonic effects of metal nanostructures have been widely explored to increase light absorption in polymer solar cells (PSCs). High absorption enhancement in a broad spectral range is highly desirable to boost the efficiency of PSCs. In this study, we numerically demonstrate broadband active layer absorption enhancement using plasmonic effects of multi-positional Ag nanospheres (Ag NSs). The Ag NSs were included simultaneously in two different locations, one at the top portion of active layer and the other at anode buffer layer/active layer interface. A high absorption enhancement of 66% was achieved in an 80 nm thick active layer by optimizing size and period of Ag NSs. The effect of active layer thickness on absorption enhancement has also been investigated. Large near-field enhancement around the NSs and efficient trapping of light within the active layer were found to be responsible for the high absorption enhancement.