Improving the Light Trapping Efficiency of Plasmonic Polymer Solar Cells through Photon Management

Abstract

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...

Au nanoparticles on ultrathin MoS2sheets for plasmonic organic solar cells

“…10 Notably, compared to the relatively small shi in PEDOT:PSS (l res ¼ 542 nm), the resonance position reached 750 nm with an increased extinction cross-section in the whole 500-800 nm range when doping the Au NPs in the PTB7/PC 71 BM blend. The large wavelength shi led to a signicantly more matched spectral overlap between the resonance wavelength and the absorption of the photoactive material (PTB7, with absorption range of 500-750 nm), 17,[43][44][45][46] suggesting an advantage if the 20 nm Au NPs can be incorporated in the active layer. The near-eld distributions of a 20 nm Au NP in different environments at the corresponding resonance wavelengths (water, l res ¼ 523 nm; PEDOT:PSS, l res ¼ 542 nm; PTB7/PC 71 BM blend, l res ¼ 750 nm) are shown in Fig.…”

Geometrical parameters controlled focusing and enhancing near field in infinite circular metal-dielectric multilayered cylinder

“…Although the surface plasmon resonance (SPR) in spherical metallic nanoparticles has been known for over one century, SPR-induced local electric field enhancement in the visible and near-infrared region has received increasing attention in recent years owing to the improved preparation method of metallic nanoparticles with complicated geometry and many promising applications. 1,2 Because of the interaction between incident electromagnetic field and SPR, the oscillating free electrons induced polarized electronic field has been greatly enhanced and could be used in surfaceenhanced Raman scattering (SERS), 3 surface enhanced fluorescence (SEF), 4,5 light trapping in solar cells, 6 and nonlinear optical response (NLO) including second harmonic generation, 7 third-order optical nonlinear effect, 8 optical limiting, 9 and optical bistability. 10 In order to obtain great enhancement of the local or near electric field, many experimental and theoretical efforts have been developed to study the local field enhancement of metallic nanoparticles with various shape and structure, such as nanorod, 11 nanoprism, 12 nanocube, 13 nanoshell, 14 and nanotube.…”

Broadband plasmon-enhanced polymer solar cells with power conversion efficiency of 9.26% using mixed Au nanoparticles

“…That means that the resonance peaks of $ 575 and $ 770 nm in aqueous solution will move to $ 615 and $825 nm in the film, respectively, covering not only the whole absorption band of PTB7: PC 71 BM, but also its cutoff edge at $ 800 nm. According to Hsiao's analysis [35], our mixed NPs will result in an effective absorption increase in the active layer and thereby an improvement in solar cell performance.…”

“…For instance, Li et al [22] used dual plasmonic nanostructures of 750 nm Ag nanogratings and 50 nm Au NPs to broaden active layer's absorption region and obtained a PCE of 8.79 70.15% with a $ 16% enhancement from 7.59 70.08%. In another work, Hsiao et al [35] combined Au nanospheres (NSs) with nanorods (NRs) which resulted in two resonant peaks with the absorption ranging from visible to near infrared (NIR) region. Through systematic analysis on film's extinction and photoluminescence (PL) spectra, they concluded that the integration of two types of Au NPs with the absorption edges covering the whole absorption spectrum is exceptionally beneficial to the performance improvements of OPVs.…”