We have systematically explored how plasmonic effects influence the characteristics of polymer photovoltaic devices (OPVs) incorporating a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). We blended gold nanoparticles (Au NPs) into the anodic buffer layer to trigger localized surface plasmon resonance (LSPR), which enhanced the performance of the OPVs without dramatically sacrificing their electrical properties. Steady state photoluminescence (PL) measurements revealed a significant increase in fluorescence intensity, which we attribute to the increased light absorption in P3HT induced by the LSPR. As a result, the rate of generation of excitons was enhanced significantly. Furthermore, dynamic PL measurements revealed that the LSPR notably reduced the lifetime of photogenerated excitons in the active blend, suggesting that interplay between the surface plasmons and excitons facilitated the charge transfer process. This phenomenon reduced the recombination level of geminate excitons and, thereby, increased the probability of exciton dissociation. Accordingly, both the photocurrents and fill factors of the OPV devices were enhanced significantly. The primary origin of this improved performance was local enhancement of the electromagnetic field surrounding the Au NPs. The power conversion efficiency of the OPV device incorporating the Au NPs improved to 4.24% from a value of 3.57% for the device fabricated without Au NPs.

In this study, we have explored how light trapping efficiency can be enhanced by using gold nanoparticles (Au NPs) of various sizes and shapes on the front of polymer solar cells (PSCs) with the active layerblends of poly(3-hexyl thiophene) and [6,6]-phenyl-C 61 -butyric acid methyl ester. The light-concentrating behavior was enhanced after we had incorporated gold nanospheres or nanorods into the anodic buffer layer [based on poly (3,4-ethylenedioxythiophene):polystyrenesulfonate] to trigger various localized surface plasmon resonance (LSPR) bands. Comparison of the optical characteristics and the performance of the PSCs prepared with and without Au NPs, and we found that the UV−vis and wavelength-dependent photoluminescent spectral data corroborated with the device performance due to the photon management by considering the light scattering and LSPR effects at the active layer. The presence of Au NPs increased the power conversion efficiency to approximately 4.3% (an enhancement of 24%). ■ INTRODUCTIONPolymer solar cells (PSCs) are promising technologies of utilizing renewable energy for mass production because of their lightweight and cost-effective production with simple processability. At present, the best power conversion efficiencies (PCEs) of bulk heterojunction (BHJ) PSCs have reached 6− 8% under AM 1.5G conditions. 1−3 After optimizing the thickness and morphology of the donor−acceptor interface of a blended film, consisting of a semiconducting polymer as the donor and a soluble fullerene as the acceptor, a BHJ photoactive layer having a thickness of approximately 200 nm would provide a high fill factor (FF) and an enhanced possibility of exciton dissociation and electrical transportation. 4−6 Furthermore, low-bandgap (LBG) materials can be used to further enhance the device performance by extending the absorption region to longer wavelength. 7−9 Although LBG materials are often associated with lower hole mobilities than are conventional poly(3-hexylthiophene) (P3HT) materials, these charge-transport problems can be overcome by decreasing the thickness of the photoactive layer, albeit with lower external quantum efficiencies (EQEs). Therefore, it is necessary to develop light-concentrating systems to enhance the light trapping efficiency of thinner active layers, especially for use in normal PSC device architectures.Recently, plasmonic light trapping has been applied to effectively enhance the light harvesting performance of solar cells, featuring either continuous metal films [through the excitation of surface plasmon polaritons (SPPs)] or metal nanoparticles [through scattering or localized surface plasmon resonance (LSPR) effects]. 10−18 In PSC devices using SPPs, the electromagnetic wave propagating along the interface between the active layer and back contact electrode should result in higher light trapping efficiency. The short-range EQE enhancement was observed, however, only at a certain excitation wavelength, which was related to the distance and height of the periodic grating structures of th...

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Current bioelectronic medicines for neurological therapies generally involve treatment with a bioelectronic system comprising a power supply unit and a bioelectrode device. Further integration of wireless and self-powered units is of practical importance for implantable bioelectronics. In this study, we developed biocompatible organic photovoltaics (OPVs) for serving as wireless electrical power supply units that can be operated under illumination with near-infrared (NIR) light, and organic bioelectronic interface (OBEI) electrode devices as neural stimulation electrodes. The OPV/OBEI integrated system is capable to provide electrical stimulation (ES) as a means of enhancing neuron-like PC12 cell differentiation and neurite outgrowth. For the OPV design, we prepared devices incorporating two photoactive material systems--β-carotene/N,N'-dioctyl-3,4,9,10-perylenedicarboximide (β-carotene/PTCDI-C8) and poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)--that exhibited open circuit voltages of 0.11 and 0.49 V, respectively, under NIR light LED (NLED) illumination. Then, we connected OBEI devices with different electrode gaps, incorporating biocompatible poly(hydroxymethylated-3,4-ethylenedioxythiophene), to OPVs to precisely tailor the direct current electric field conditions during the culturing of PC12 cells. This NIR light-driven OPV/OBEI system could be engineered to provide tunable control over the electric field (from 220 to 980 mV mm(-1)) to promote 64% enhancement in the neurite length, direct the neurite orientation on chips, or both. The OPV/OBEI integrated systems under NIR illumination appear to function as effective power delivery platforms that should meet the requirements for wirelessly offering medical ES to a portion of the nervous system; they might also be a key technology for the development of next-generation implantable bioelectronics.