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Evaluating six main rivers and six lakes in Beihuan water system (BWS) and diagnosing the limiting factors of eco-health were conducted for the ecohealth assessment and ecological restoration division of urban water system (UWS) for Beijing. The results indicated that Jingmi River and Nanchang River were in a healthy state, the degree of membership to unhealthy were 0.358, 0.392, respectively; while Yongding River, Beihucheng River, Liangma River, Tongzi River and six lakes were in an unhealthy state, their degree of membership to unhealthy were between 0.459 and 0.927. The order of that was Liangma>Beihucheng>Tongzi>Yongding>six lakes>Jingmi>Nanchang, in which Liangma Rivers of that was over 0.8. The problems of Rivers and lakes in BWS are different. Jingmi River and Nanchang River were ecotype limiting; Yongding River, Tongzi River and six lakes were water quality and ecotype limiting. Beihucheng River and Liangma River were water quantity, water quality and ecotype limiting. BWS could be divided into 3 restoration divisions, pollution control division including Yongding River, Tongzi River and six lakes; Jingmi River and Nanchang River were ecological restoration zone, while Beihucheng River and Liangma River were in comprehensive improvement zone. Restoration potentiality of Jingmi River and Nanchang River were higher, and Liangma River was hardest to restore. The results suggest a new idea to evaluate the impact of human and environmental factors on UWS. [ABSTRACT FROM AUTHOR]

Solar cells based on organic molecules or conjugated polymers attract great attention due to their unique advantages, such as low cost, and their use in flexible devices, but are still limited by their low power conversion efficiency (PCE). To improve the PCEs of polymer solar cells, more efforts have been made to increase short-circuit current (Jsc) or open-circuit voltage (Voc). However, the trade-off between Jscand Vocin bulk heterojunctions solar cells makes it tricky to find a polymer with a low band gap to efficiently absorb photons in the visible and near infrared region of the solar spectrum, while maintaining a high Vocin solar cells. Therefore, it is crucial to design and synthesize polymers with energy levels aligning with the LUMO (lowest unoccupied molecular orbital) of an electron acceptor to minimize the LUMO level difference between donor and acceptor to keep enough driving force for charge generation, thereby maximizing photovoltage in solar cells. Here a novel copolymer APFO-Green 9 was synthesized. Polymer solar cells based on APFO-Green 9 blended with a derivative of fullerene demonstrate high photovoltage by fine tuning the HOMO and LUMO level of APFO-Green 9. Solar cells based on APFO-Green 9 and [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) present a photoresponse extended to 900 nm with Jscof 6.5 mA cm−2, Vocof 0.81 V and PCE of 2.3% under illumination of AM1.5 with light intensity of 100 mW cm−2. As a low band gap polymer with a Vocbigger than 0.8 V, APFO-Green 9 is a promising candidate for efficient tandem solar cells. [ABSTRACT FROM AUTHOR]

Organic bulk heterojunction (BHJ) solar cells based on a dicyanovinyl-substituted oligothiophene as a donor and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as an acceptor were fabricated and characterized. The oligothiophene derivative can absorb long wavelength photons of the solar radiation, which makes the solar cells with an optimized weight ratio of 1:1.4 have a decent short-circuit current density (12.4 mA/cm2) and open-circuit voltage (0.88 V) under AM 1.5G illumination with an intensity of 100 mW/cm2. A power conversion efficiency (PCE) of 3.7% is achieved, which is among the best PCEs of solution processed small molecule BHJ solar cells. [ABSTRACT FROM AUTHOR]

Arrays of reflective multijunction polymer solar cell were demonstrated by folding four separated cells fabricated on a single plastic substrate using conducting polymer poly(3, 4-ethylene-dioxythiophene):polystyrenesulfonate as an anode. The combination of flexible substrate and polymer solar cells (PSCs) makes the construction of multifolded PSCs on one substrate possible. The power conversion efficiency (PCE) of the multifolded reflective PSCs was enhanced by 62%±12% with the folded opening angle of 30° compared to the planar cells. In series connection of four solar cells, an open-circuit voltage (Voc) of 3.65 V was obtained. [ABSTRACT FROM AUTHOR]

Bilayer polymer anode composed of poly(3,4-ethylene-dioxythiophene): polystyrenesulfonate (PEDOT:PSS) (PH500) and PEDOT:PSS (Baytron P VP Al 4083) was used to construct flexible polymer solar cells on plastic substrates polyethylene terephthalate (PET) with a device structure of PET/polymer anode/APFO-3:PCBM/LiF/Al. The power conversion efficiency (PCE) of the indium tin oxide (ITO)-free solar cells achieved 2.2% under illumination of AM1.5 (100 mW cm-2), which is 80% of the PCE of the reference cells with ITO on glass. The simplicity of preparing bilayer polymer anode and the comparable performance achieved in the flexible solar cells made the bilayer polymer anode an alternative to ITO for flexible solar cells produced by printing technology. [ABSTRACT FROM AUTHOR]

Both electron and hole mobilities have been simultaneously measured through charge extraction by linearly increasing voltage on polymer heterojunction solar cells with varying stoichiometry of polymer and acceptor. The polymer is a low band gap copolymer of fluorene, thiophene, and electron accepting groups named APFO-Green 5, and the acceptor is [6,6]-phenyl-C61-butyric acid methylester. Results are correlated to field effect transistor measurements on the same material system. A monotonous increase in mobility for both carrier types is observed with increased acceptor loading. [ABSTRACT FROM AUTHOR]

The article focuses on the Point-of-care testing (POCT) has broad applications in resource-limited settings; and mentions the ideal Deoxyribonucleic acid (DNA) POCT system needs not only to be able to process diverse types of samples but also to be able to detect the multiple forms of DNA targets including pathogen-specific DNA sequences, gene mutations, single-nucleotide polymorphisms (SNPs), and allele genes.

We have studied the influence of three different fullerene derivatives on the charge generation and recombination dynamics of polymer/fullerene bulk heterojunction (BHJ) solar cell blends. Charge generation in APFO3/[70]PCBM and APFO3/[60]PCBM is very similar and somewhat slower than charge generation in APFO3/[70]BTPF. This difference qualitatively matches the trend in free energy change of electron transfer estimated from the LUMO energies of the polymer and fullerene derivatives. The first order (geminate) charge recombination rate is significantly different for the three fullerene derivatives studied and increases in the order APFO3/[70]PCBM < APFO3/[60]PCBM < APFO3/[70]BTPF. The variation in electron transfer rate cannot be explained from the LUMO energies of the fullerene derivatives and single-step electron transfer in the Marcus inverted region and simple considerations of expected trends for the reorganization energy and free energy change. Instead we suggest that geminate charge recombination occurs from a state where electrons and holes have separated to different distances in the various materials because of an initially high charge mobility, different for different materials. In a BHJ thin film this charge separation distance is not sufficient to overcome the electrostatic attraction between electrons and holes and geminate recombination occurs on the nanosecond to hundreds of nanoseconds time scale. In a BHJ solar cell, we suggest that the internal electric field in combination with polarization effects and the dynamic nature of polarons are key features to overcome electron-hole interactions to form free extractable charges. [ABSTRACT FROM AUTHOR]

In this article we report the weak but omnipresent electroluminescence (EL) from several types of. organic polymer:fullerene bulk heterojunction solar cells biased in the forward direction. The light emitted from blends of some commonly used polymers and the fullerene molecule is significantly different from that of any of the pure materials comprising the blend. The lower energy of the blend EL is found to correlate with both the voltage onset of emission and the open-circuit voltage of the photovoltaic cell under solar illumination. We accordingly interpret the emission to originate from interfacial charge transfer state recombination and emphasize EL as a very valuable tool to characterize the charge transfer state present in donor/acceptor organic photovoltaic (OPV) cells. [ABSTRACT FROM AUTHOR]

The article describes how to design planar polymers with effective chain packing in film to facilitate charge carrier transport for photovoltaic application. Poly(2-(5-(5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-7-yl)thiophen-2-yl)-9-octyl-9H-carbazole) (HXS-1), a copolymer, was developed and used in solar cells. HXS -1 is designed with two octyloxy chains on the benzothiazole ring and an octyl chain on the carbazole ring to achieve planar polymer conformation.