Showing papers by "Xiong Gong published in 2013"

A Series of New Medium‐Bandgap Conjugated Polymers Based on Naphtho[1,2‐c:5,6‐c]bis(2‐octyl‐[1,2,3]triazole) for High‐Performance Polymer Solar Cells

Abstract: A series of novel conjugated copolymers based on naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) (TZNT) are synthesized. These copolymers exhibit medium bandgaps of ≈1.9 eV. One of them demonstrates a high performance of up to 6.10% power conversion efficiency in a bulk-heterojunction (BHJ) solar-cell device. The performance can be further enhanced to 7.11% when applied in an inverted device architecture, using PF3 N-OX as an interfacial modifier.

Molecular weight effect on the efficiency of polymer solar cells.

Abstract: In this study, we report the investigation of the influence of molecular weight (MW) on power conversion efficiency (PCE) of bulk heterojunction (BHJ) polymer solar cells (PSCs). It was found that PCEs of PSCs fabricated by poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) blended with [6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) as the active layer, are significantly enhanced from 5.41 to 6.27 and 8.50% along with the MW of PTB7 increased from 18 to 40 and 128 kg/mol, respectively. This enhancement is attributed to the enhanced light absorption and increased charge carrier mobility of PTB7 with high MW, and a proper phase separation in BHJ composite of PTB7:PC71BM interpenetrating network. All these results demonstrate that the MW of donor polymer plays an important role in the performance of BHJ PSCs.

Dual Functionality of Antimicrobial and Antifouling of Poly(N-hydroxyethylacrylamide)/Salicylate Hydrogels

Abstract: The emergence and reemergence of microbial infection demand an urgent response to develop effective biomaterials that prevent biofilm formation and associated bacterial infection. In this work, we have synthesized and characterized hybrid poly(N-hydroxyethylacrylamide) (polyHEAA)/salicylate (SA) hydrogels with integrated antifouling and antimicrobial capacities. The antifouling efficacy of polyHEAA hydrogels was examined via exposure to proteins, cells, and bacteria, while the antimicrobial activity of SA-treated polyHEAA hydrogels was investigated against both Gram-negative Escherichia coli RP437 and Gram-positive Staphylococcus epidermidis. The results showed that polyHEAA/SA hydrogels exhibited high surface resistance to protein adsorption, cell adhesion, and bacteria attachment. The polyHEAA hydrogels were also characterized by their water content and state of water, revealing a strong ability to contain and retain high nonfreezable water content. This work demonstrates that the hybrid polyHEAA/SA hyd...

Solution-Processed High-Detectivity Near-Infrared Polymer Photodetectors Fabricated by a Novel Low-Bandgap Semiconducting Polymer

Abstract: High-detectivity near-infrared (NIR) polymer photodetectors (PDs) fabricated by a novel low-bandgap semiconducting polymer blended with fullerene derivatives are reported. Operating at room temperature, the polymer PDs have a spectral response from 400 to 1100 nm. By incorporation of an alcohol/water-soluble polymer as a cathode interlayer in bulk heterojunction polymer PDs, the polymer PDs exhibit a high detectivity of 1.75 × 1013 cm•Hz1/2/W at 800 nm. These results demonstrated that the NIR polymer PDs are comparable to Si-based PDs.

Solution-Processed Fe3O4 Magnetic Nanoparticle Thin Film Aligned by an External Magnetostatic Field as a Hole Extraction Layer for Polymer Solar Cells

Abstract: We report, for the first time, the effect of a solution-processed Fe3O4 magnetic nanoparticle (MNP) thin film and a Fe3O4 MNP thin film aligned by an external magnetostatic field, used as a hole extraction layer (HEL), respectively, in polymer solar cells (PSCs). The thin film of a Fe3O4 MNP shows a smoother surface, better transparency, and higher electrical conductivity than that of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin layer. Moreover, the thin film of a Fe3O4 MNP aligned by an external magnetostatic field possesses an enhanced electrical conductivity and lower internal series resistance, thus leading to greater than 13% enhancement in the power conversion efficiency of PSCs than those using a PEDOT:PSS thin film. It was also found that PSCs incorporated with a Fe3O4 MNP shows better stability compared with those using PEDOT:PSS as an anode buffer layer. These results demonstrated that utilization of a Fe3O4 MNP as a HEL in PSCs blazes a trail to achieve highly effi...

Pyridinium salt-based molecules as cathode interlayers for enhanced performance in polymer solar cells

Abstract: A series of water/alcohol-soluble small molecules based on electron-deficient pyridinium salts namely BTPS, BnPS and F8PS were successfully synthesized. Their photophysical and electrochemical properties were thoroughly studied. Due to its good film-forming ability, F8PS was employed as a cathode interlayer in an organic photovoltaic cell. Simultaneous enhancements in open-circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF) were achieved, and the power conversion efficiency (PCE) was increased from 4.32% to 6.56% compared to the device based on the bare Al cathode. Voc was significantly improved from 0.76 V to 0.94 V, and it is one of the best results reported in literature to date for polymer solar cells (PSCs) based on the active layer of poly [N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′- di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT):[6,6]-phenyl-C71-butyric acid methylester (PC71BM). The greatly increased Voc may be due to the interface dipoles generated by F8PS. It was also demonstrated that post treatment of the active layer with ethanol gave an improvement of the overall device efficiency from the initial 4.32% to 5.55%, compared to the device with the bare Al cathode. Therefore, the improvement in performance after pyridinium salt deposition may be due to a combination of the effects of ethanol treatment and the presence of the thin pyridinium salt layer. The good water/alcohol solubility, ideal HOMO/LUMO energy levels and the excellent electron transfer/collection ability of the hydrophilic pyridinium salt derivatives makes them a promising family of electron transport materials for highly efficient PSCs.

Fine-Tuning of Fluorinated Thieno[3,4-b]thiophene Copolymer for Efficient Polymer Solar Cells

Abstract: Novel low band gap fluorinated copolymers have been synthesized and characterized. The performance of inverted polymer solar cells made by these fluorinated copolymers blended with fullerene derivatives was also investigated. The studies of the effect of fluorine units on the electronic properties and the thin film morphologies of fluorinated copolymers demonstrated that an optimal window of 20–40% fluorine units coupled with thieno[3,4-b]thiopehene exists for a maximum hole mobility that correlated well with a dispersed interconnected morphology of the fluorinated copolymer, thus enhancing the performance of polymer solar cells. More fluorine units coupled with thieno[3,4-b]thiopehene adversely affected the phase morphology to coarsen that in turn reduced polymer solar cells performance. Nevertheless, the polymer solar cell performance of the highest fluorinated content polymer was twice as much as the nonfluorinated copolymer. These results indicate that the electronic properties as well as the thin fil...

Water-soluble CdTe quantum dots as an anode interlayer for solution-processed near infrared polymer photodetectors.

Abstract: Water-soluble cadmium telluride (CdTe) quantum dots (QDs) used as an anode interlayer in solution-processed near infrared (NIR) polymer photodetectors (PDs) were demonstrated. Polymer PDs incorporated with CdTe QDs as an anode interlayer exhibited 10-fold suppressed dark current density and analogous photocurrent density relative to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which resulted in enhanced detectivities over 1011 Jones in the spectral range from 350 nm to 900 nm. Moreover, with the substitution of PEDOT:PSS by CdTe QDs, the stability of unencapsulated NIR polymer PDs was extended up to 650 hours, which is more than 3 times longer than those with PEDOT:PSS as an anode interlayer. These results indicated that CdTe QDs can be utilized as a solution-processable alternative to PEDOT:PSS as an anode interlayer for high performance NIR polymer PDs.

Enhanced Efficiency Polymer Solar Cells Using Aligned Magnetic Nanoparticles

Abstract: Polymer solar cells with enhanced efficiency utilize an active layer formed of a composite of polymer/fullerene and Fe 3 O 4 nanoparticles. During the formation of the solar cell, the composite mixture is subjected to an external magnetic field that causes the nanoparticles to align their magnetic dipole moments along the direction of the magnetic field, so as to form a plurality of Fe 3 O 4 nanochains. These nanochains serve to adjust the morphology and phase separation of the polymer/fullerene, and also serve to induce an internal electrical field by spin-polarization of the nanochains serve to increase the charge separation and charge transport processes in the solar cell, enhancing the short-current density (J sc ) and ultimately, the photoelectric converted efficiency (PCE) of the solar cell.

Broadband polymer photodetectors using zinc oxide nanowire as an electron-transporting layer

Abstract: A polymer photodetector has an inverted device structure that includes an indium-tin-oxide (ITO) cathode that is separated from an anode by an active layer. The active layer is formed as a composite of conjugated polymers, such as PDDTT and PCBM. IN addition, a cathode buffer layer formed as an matrix of ZnO nanowires is disposed upon the ITO cathode, while a MoO 3 anode buffer layer is disposed between a high work-function metal anode and the active layer. During operation of the photodetector, the ZnO nanowires allows the effective extraction of electrons and the effective blocking of holes from the active layer to the cathode. Thus, allowing the polymer photodetector to achieve a spectral response and detectivity that is similar to that of inorganic photodetectors.

Towards high performance inverted polymer solar cells

Abstract: Attempts to develop inverted polymer solar cells (PSCs) as required for achieving high efficiency and good stability have, however, met with limited success. Here, we report that a high efficiency of 8.4% was achieved for inverted PSCs. This high efficiency was obtained through interfacial engineering of solution-processed electron extraction layer, leading to facilitate electron transport and suppress bimolecular recombination. These results provided an important progress for solution-processed PSCs, and demonstrated that the inverted PSCs are comparable with the conventional PSCs.

Electron Donor-Fullerene Conjugated Molecules for Organic Photovoltaic Cells

Abstract: A photovoltaic cell has an active area formed electron donor-fullerene conjugated molecules. The electron donor is formed of a polymer, which is conjugated with an electron acceptor, such as fullerene. By conjugating the fullerene, such as C 60 , with electron donor moieties, such as that of the polymer, double channels are formed therebetween, whereby one channel provides hole transport and the other channel provides electron transport. As a result, the electronic coupling between the fullerene and the electron donor moiety leads to increased short-circuit current density (J sc ) and increased open-circuit voltage (V oc ), resulting in high power conversion efficacy (PCE) in the solar cell.

An organic polymer photo device with broadband response and increased photo-responsitivity

Abstract: An organic polymer photo device with broadband response and high photo- responsitivity includes an anode terminal with a hole transporting network, and a cathode terminal with an electron transporting network. Positioned in electrical communication with the hole transporting network and the electron transporting network is a blended material that has at least one organic polymer light absorbing component. The organic light absorbing component is configured to have a collection length that is larger than the distance to the nearest electron transporting network and hole transporting network. As such, the blended material forms a light absorbing area that has a dimension that is greater than the collection length of the organic polymer light absorbing component.