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This paper reports a high-efficiency approach to improve the photoelectric-conversion efficiency of thin-film solar cells by plasmonic scattering and local near-field amplification of silver nanoparticles. We employ a three-dimensional (3D) electromagnetic model and use the finite-difference time-domain (FDTD) and rigorously coupled-wave analysis methods to investigate the interaction of light with such a metallic particle. The numerical results show that the absorption and scattering spectra depend upon the properties of the embedded particles and the refractive index of the surrounding material. Strong redshifts and high-order modes are observed in the response spectrum with the increase of the particle size and the refractive index of the surrounding material. With an optimized design having P = 2 0 0 , H = 1 3 5 , and D = 7 0  nm, the performance of cell device is improved over a broad spectral range. Moreover, some of the absorption, in the resonance region, is beyond the Yablonovitch limit. The corresponding light-generated photocurrent is increased from 14.2 mA/cm2 to 18.3 mA/cm2, with a 28.9% enhancement compared with conventional cells with antireflective coatings (ARCs). [ABSTRACT FROM AUTHOR]

A subtle modification of the device surface is able to reduce optical loss and to further achieve high photoelectric conversion efficiency for thin film solar cells. This work shows the manipulation properties of subwavelength periodic structures on incident light at air/glass surface. In order to explore the mechanisms of optical loss, the spectral response and energy distribution of light are investigated by using rigorous coupled wave analysis and finite difference time domain methods. Calculation results show that the diffraction scattering and gradient refraction index play a significant role for better photon harvesting. With an optimized design of P = 2 7 0 nm, f = 0. 3 5 , and hemispherical shape structure, obvious improvement in transmittance, external quantum efficiency and photo-generated current is achieved. The photoelectric conversion efficiencies of amorphous silicon thin film cells with an absorbing layer thickness of 400 nm is 8.04%, improved by 5.9% compared with the flat cell of equivalent size. An effective light strategy was developed, by introducing subwavelength periodic structures (SWPS) into amorphous silicon thin film solar cells, which made the optical loss from cell surfaces conspicuously suppressed. It was found that hemisphere shaped structure has the best performance for photon harvesting. The optical design yields a power conversion efficiency of 8.04%, thanks to the diffraction scattering and gradient refraction index provided by SWPS. [ABSTRACT FROM AUTHOR]

A new organic small molecule, DCA3TBDF, with a 2D benzo[1,2-b:4,5-b']difuran (BDF) moiety as the central core and octyl cyanoacetate units as the end-capped blocks, was designed and synthesized for solution-processed bulk heterojunction solar cells. DCA3TBDF possesses good solubility in common organic solvents such as toluene, CH2Cl2, chlorobenzene, and CHCl3 and good thermal stability with an onset decomposition temperature with 5% weight-loss occurring at 361 °C. The DCA3TBDF thin film showed a broad absorption at λ=320-700 nm and high crystallinity. Small-molecule organic solar cells based on DCA3TBDF and [6,6]- phenyl-C61-butyric acid methyl ester demonstrated promising power conversion efficiency with a high fill factor under the illumination of AM 1.5G (100 mWcm-2). [ABSTRACT FROM AUTHOR]

ABSTRACT Poly{[2,7-(9,9-bis-(1-(2-(2-methoxyethoxy)ethoxy)ethyl)-fluorene)]-alt-[5,5-(4,7-di-2′-thienyl-2,1,3-benzothiadiazole)]} (EO-PF-DTBT) was synthesized by Suzuki coupling reaction. The polymer is soluble in common organic solvent, such as toluene, THF, and chloroform, and it also shows solubility in polar solvent, such as cyclopentanone. Solar cells based on EO-PF-DTBT and PC61BM show maximum power conversion efficiency of 2.65% with an open circuit voltage ( VOC) of 0.86 V, a short circuit current density ( JSC) of 6.10 mA/cm2, and a fill factor of 51% under AM 1.5G illumination at 100 mW/cm2, which is the best results for fluorene and 4,7-di-2-thienyl-2,1,3-benzothiadiazole copolymers and PC61BM blend. The 1,8-diiodooctane can work well to reduce the over-aggregated phase structure in polymer solar cells. Our results suggest that the introducing high hydrophilic side chain into conjugated polymer donor materials can tune the aggregation structure and improve the solar cells performances. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40478. [ABSTRACT FROM AUTHOR]

A new thiazolothiazole based small molecule (DTTz-DTBTT) has been designed and synthesized. The small molecule exhibited good thermal stability and excellent solubility. The optical gap of DTTz-DTBTT was estimated to be 1.65 eV. The solution-processed photovoltaic device based on DTTz-DTBTT and PC61BM exhibited a power conversion efficiency of 1.64%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Deep HOMO benzodithiophene (BDT) and benzotriazole based molecule is reported. [•] Solar cells show high Voc of 0.93V with PCEs of 3.61% device. [•] Solar cells also can show high FF of 72% with PCEs of 2.31% device. [ABSTRACT FROM AUTHOR]

Highlights: [•] First thienoisoindigo-based small molecule photovoltaic material is reported. [•] Solar cells show near-infrared response (around 900–1000nm). [•] Small molecule solar cells device is solution-processing. [Copyright &y& Elsevier]

Abstract: A new easily-accessible solution-processed oligomer, with an isoindigo group as an electron acceptor and a thieno[3,2-b]thiophene flanked by thiophenes as electron donors, has been synthesized by a Stille coupling reaction. Through introducing the extended π-conjugated groups into isoindigo, the electro-optical properties of the material can be fine-tuned. The isoindigo oligomer has a broad absorption in the region from 300 to 800 nm with a narrow bandgap (1.54 eV), which is believed to be an ideal bandgap as donor materials. The oligomer possesses low HOMO energy level (−5.39 eV). The potential of optical and electronic properties encouraged us to explore the photovoltaic performance using the oligomer as the donor material in bulk heterojunction organic solar cell along with 6,6-phenyl-C61-butyric acid methyl ester as the acceptor. The solar cell based on the oligomer with an inverted device configuration provided a power conversion efficiency of 1.41% under the AM 1.5G illumination with an intensity of 100 mW cm−2 from a solar simulator. [Copyright &y& Elsevier]

• Bioinspired moth-eye-like nanostructures overcomes limitation of weak absorption. • A non- abrupt effective refractive index curve plays a key role for the light harvesting. • Moth-eye-like nanostructures fabricated exhibit ultralow reflections. Herein, bioinspired moth-eye-like nanostructures are presented as a possible solution for overcoming the limitation of weak absorption by thin film silicon solar cells. The interaction mechanism between the incident wave and such an artificial nanostructure is revealed by using the finite-difference time-domain method. Optical simulations show that the addition of biomimetic nanostructured surface reduces the refractive indices difference from external media environment to cell devices, thereby leads more incident light propagated into the active material. The optical design yield power conversion efficiencies of 14.6% and 17.5% for 2 and 5 μm thick absorbing layers, respectively. Further analysis depended on the equivalent medium theory demonstrates that a smooth, non– abrupt effective refractive index curve plays a key role for the light harvesting. The proposed method of addressing the weak absorption problem by thin film solar cells shows great promise. [ABSTRACT FROM AUTHOR]

Highlights: [•] Isoindigo-based compound is synthesized. [•] The solar cells device shows high open-circuit voltage of 1.0V. [•] Small molecule solar cells device is solution-processing. [ABSTRACT FROM AUTHOR]