Wind speed is an important meteorological factor and is a parameter used to determine the air pollution assessment and the economic feasibility of wind energy as a renewable resource. In particular, ...the measurement of long-term average wind speed plays a role in the estimating of chronic exposure of air pollution and the siting of wind turbines; thus this study focuses on annual and monthly wind speed. However, due to spatially sparse and irregular meteorological stations, interpolation methods are used to predict unsampled areas. Therefore, the purpose of this study is to determine the optimal interpolation method among deterministic and geostatistical interpolation techniques. While most interpolation methods rely on spatial coverage and do not give an accurate characterization of small-area variations, cokriging and regression kriging (RK) can resolve the drawback by containing regional heterogeneity as auxiliary variables. In addition, this study applied isotropic and anisotropic approaches to geostatistical interpolations. This study showed that among the sampled methods, anisotropic RK with regional heterogeneous terrains and solar insolation was most likely to produce the best estimate for the highest accuracy for annual and monthly wind speeds with relatively unbiased spatial errors. In addition, while extreme wind speed decreases the accuracy of wind speed prediction, the number, range, and variance of observed wind speed significantly influence the accuracy of wind speed prediction.
All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability ...in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymer acceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared with polymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices.
The molecular weight of a conjugated polymer is one of the key factors determining the electrical, morphological, and mechanical properties as well as its solubility in organic solvents and ...miscibility with other polymers. In this study, a series of semicrystalline poly(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzoc1,2,5thiadiazole) (PPDT2FBT) polymers with different number-average molecular weights (M n’s) (PPDT2FBT L , M n = 12 kg/mol; PPDT2FBT M , M n= 24 kg/mol; PPDT2FBT H , M n= 40 kg/mol) were synthesized, and their photovoltaic properties as electron donors for all-polymer solar cells (all-PSCs) with polyN,N′-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl-alt-5,5′-(2,2′-bithiophene) (P(NDI2OD-T2)) acceptor were studied. The M n effect of PPDT2FBT on the structural, morphological, electrical, and photovoltaic properties was systematically investigated. In particular, tuning the M n induced dramatic effects on the aggregation behaviors of the polymers and their bulk heterojunction morphology of all-PSCs, which was thoroughly examined by grazing incident X-ray scattering, resonant soft X-ray scattering, and other microscopy measurements. High M n PPDT2FBT H promoted a strong “face-on” geometry in the blend film, suppressed the formation of an excessively large crystalline domain, and facilitated molecularly intermixed phases with P(NDI2OD-T2). Therefore, the optimized all-PSCs based on PPDT2FBT H /P(NDI2OD-T2) showed substantially higher hole and electron mobilities than those of PPDT2FBT L /P(NDI2OD-T2), leading to a power conversion efficiency exceeding 5%, which is one of the highest values for all-PSCs reported thus far.
The effectiveness of side‐chain engineering is demonstrated to produce highly efficient all‐polymer solar cells (efficiency of 5.96%) using a series of naphthalene diimide‐based polymer acceptors ...with controlled side chains. The dramatic changes in the polymer packing, blend morphology, and electron mobility of all‐polymer solar cells elucidate clear trends in the photovoltaic performances.
In the United States (US), one of the effects of urban sprawl is more vehicular travel. The increase in emissions from road traffic renders air quality management unsuccessful, in spite of the ...efforts of the US Environmental Protection Agency (EPA), operating under the Clean Air Act, which does not regulate land use. As an alternative to urban sprawl, the US-EPA has initiated smart growth strategies based on compact development. In this study, the impacts of metropolitan-level urban form, as a measure of urban compactness/sprawl, was explored with respect to air quality in terms of NOx and PM2.5 emissions on the road and NO2 and PM2.5 concentrations in US metropolitan areas. Ordinary least squares (OLS) and two-level regression models that control for metropolitan-level socioeconomic and local-level geographic covariates were established. The results showed that high land use mixing is one of the compactness/sprawl factors (i.e., low sprawl) that reduces per-person NOx and PM2.5 emissions on the road. While metropolitan-level urban form (i.e. high compactness) had a negative effect on PM2.5 concentrations, local environmental conditions, such as local ambient roads and emissions facilities, had greater impacts on NO2 and PM2.5 concentrations than the urban form. Based on the findings in this study, urban planners and decision makers need to establish policies and practices at two scales when planning urban development: (1) the reduction of emissions from road traffic by managing metropolitan-level urban form and (2) the reduction of emissions concentrations through managing local emissions sources near populated areas.
•High land use mixing at metropolitan-level reduced NOx and PM2.5 from road traffic.•High compactness at metropolitan-level only had a negative effect on PM2.5 concentrations.•Local-level environmental conditions had greater effect on NO2 and PM2.5 concentrations than metropolitan-level urban form.
Tuning the side chains of conjugated polymers is a simple, yet effective strategy for modulating their structural and electrical properties, but their impact on n‐type conjugated polymers has not ...been studied extensively, particularly in the area of all‐polymer solar cells (all‐PSCs). Herein, the effects of side chain engineering of P(NDI2OD‐T2) polymer (also known as Polyera Activink N2200) are investigated, which is the most widely used n‐type polymer in all‐PSCs and organic field‐effect transistors (OFETs), on their structural and electronic properties. A series of naphthalenediimide‐bithiophene‐based copolymers (P(NDIR‐T2)) is synthesized, with different side chains (R) of 2‐hexyldecyl (2‐HD), 2‐octyldodecyl (2‐OD), and 2‐decyltetradecyl (2‐DT). The P(NDI2HD‐T2) exhibits more noticeable crystalline behaviors than P(NDI2OD‐T2) and P(NDI2DT‐T2), thereby facilitating superior 3D charge transport. For example, the P(NDI2HD‐T2) shows the highest OFET electron mobility (1.90 cm2 V−1 s−1). Also, a series of all‐PSCs is produced using different electron donors of PTB7‐Th, PTB7, and PPDT2FBT. The P(NDI2HD‐T2) based all‐PSCs produce much higher power conversion efficiency (PCE) irrespective of the electron donors. In particular, the PTB7‐Th:P(NDI2HD‐T2) forms highly ordered, strong face‐on interchain stackings, and has better intermixed bulk‐heterojunction morphology, producing the highest PCE of 6.11% that has been obtained by P(NDIR‐T2) based all‐PSCs to date.
The effect of side chain modification of naphthalenediimide–bithiophene (NDI‐T2)‐based n‐type polymers on their structural and electronic properties has been investigated. The P(NDI2HD‐T2)‐based all‐polymer solar cells produce much better performance than other NDI‐T2‐based devices (i.e., P(NDI2OD‐T2) (Polyera Activink N2200)) irrespective of the electron donor due to superb electron transport ability of P(NDI2HD‐T2).
•Urban forms have different associations with PM2.5 concentrations depending on scales and types.•At the metropolitan scale, urban form is related to travel behavior.•At the neighborhood scale, urban ...form is related to proximate emission sources.
This study explores the relationship between urban form at the metropolitan and neighborhood scale and fine particulate matter (PM2.5) concentrations by establishing multi-level regression models. This study has different assumptions about urban form depending on the scale used. While at the metropolitan scale, the urban form is related to the change in travel behavior, at the neighborhood scale, it is related to proximate emission sources such as roads, emissions facilities, employment centers, etc. The study shows that at the metropolitan scale, higher urban fragments, population density, and road density are associated with higher PM2.5 concentrations; higher job-resident balance and accessibility to schools are associated with lower PM2.5. At the neighborhood scale, a higher density of the nearby emission sources and higher accessibility to destinations are associated with higher PM2.5 concentrations. Urban fragments and land use mix have consistent impacts on air quality compared to preexisting studies. While population density and road density have two conflicting assumptions regarding PM2.5, in this study, the net effect of population density and road density on air quality is negative. Accessibility to destinations has different associations with PM2.5 depending on the scale of urban form measurement. At the metropolitan scale, high accessibility to destinations lessens PM2.5 concentrations by reducing vehicle distance. On the other hand, at the neighborhood scale, high accessibility to destinations makes it close to areas, which concentrate air emissions. We suggest that urban planners and decision-makers establish different strategies depending on urban form types when there are urban development plans.
We report eco- and human-friendly fabrication of organic field-effect transistors (OFETs) and polymer solar cells (PSCs) using only ethanol as a processing solvent at ambient condition, in stark ...contrast to that involving the use of halogenated and/or aromatic solvents. New ethanol-processable electroactive materials, p-type polymer (PPDT2FBT-A) and n-type bis-adduct fullerene acceptor (Bis-C60-A) are designed rationally by incorporation of oligoethylene glycol (OEG) side-chains. By ethanol processing, PPDT2FBT-A shows a broad light absorption in the range of 300–700 nm and highly crystalline interchain ordering with out-of-plane interlamellar scattering up to (400) with strong π–π stacking. As a result, the ethanol-processed PPDT2FBT-A OFETs yield high charge-carrier mobilities up to 1.0 × 10–2 cm2 V–1 s–1, which is the highest value reported to date from alcohol-processed devices. Importantly, the ethanol-processed PPDT2FBT-A OFET outperformed that processed using typical processing solvent, chlorobenzene (CB), with ∼10-fold enhancement in hole mobility, because the highly edge-on oriented packing of PPDT2FBT-A was produced by ethanol-process. Also, for the first time, significant photovoltaic performance was achieved for the ethanol-processed device of PPDT2FBT-A and Bis-C60-A due to the formation of an interpenetrating nanofibrillar morphology of highly crystalline PPDT2FBT-A polymers. The relationships between molecular structure, nanoscale morphology and electronic properties within ethanol-processed OFETs and PSCs were elucidated by comparing to typical CB-processed devices. These comparisons provide important guidelines for the design of new ethanol/water-soluble active layer materials and their use in the development of green solvent-processed efficient OFETs and PSCs.
This study aims to investigate the effects of urban and forest areas measured in three dimensions on seasonal temperature over forty years in South Korean cities. We measure the urban and forest ...areas at the city, neighborhood, and spatially clustered levels in four periods every ten years. Using Hot Spot Analysis (Getis-Ord Gi*), this study detects the spatially clustered urban and forest areas. We establish a multilevel regression model to explore the relationship between urban and forest areas measured in three dimensions, as well as seasonal temperatures. The study shows that while spatially clustered urban and forest areas have consistent associations with the four seasonal temperatures, urban and forest areas at the city scale have different associations with the seasonal temperature, depending on the season. When spatially clustered urban areas increase by 10 km2, four seasonal temperatures increase by about 0.0016–0.0067 Celsius degree (°C); on the other hand, when spatially clustered forest areas increase by 10 km2, four seasonal temperatures decrease by about 0.0001–0.0016 °C. At the neighborhood level, urban and forest areas are negatively associated with the four seasonal temperatures. The results of this study can be utilized by urban planners and policymakers to establish land use planning or policy by providing evidence of whether land use plans should be established and at what scales to manage regional thermal environments. To alleviate seasonal warming, we recommend increasing forest areas at the neighborhood and spatially clustered levels and controlling the size of spatially clustered urban areas.
•Spatially clustered urban areas are positively associated with seasonal temperatures.•Spatially clustered forest areas are negatively associated with seasonal temperatures.•To alleviate regional warming, interconnected forested areas are recommended.•Regulating the expansion of urban areas is also recommended.
The branching point of the side‐chain of naphthalenediimide (NDI)‐based conjugated polymers is systematically controlled by incorporating four different side‐chains, i.e., 2‐hexyloctyl (P(NDI1‐T)), ...3‐hexylnonyl (P(NDI2‐T)), 4‐hexyldecyl (P(NDI3‐T)), and 5‐hexylundecyl (P(NDI4‐T)). When the branching point is located farther away from the conjugated backbones, steric hindrance around the backbone is relaxed and the intermolecular interactions between the polymer chains become stronger, which promotes the formation of crystalline structures in thin film state. In particular, thermally annealed films of P(NDI3‐T) and P(NDI4‐T), which have branching points far away from the backbone, possess more‐developed bimodal structure along both the face‐on and edge‐on orientations. Consequently, the field‐effect electron mobilities of P(NDIm‐T) polymers are monotonically increased from 0.03 cm2 V−1 s−1 in P(NDI1‐T) to 0.22 cm2 V−1 s−1 in P(NDI4‐T), accompanied by reduced activation energy and contact resistance of the thin films. In addition, when the series of P(NDIm‐T) polymers is applied in all‐polymer solar cells (all‐PSCs) as electron acceptor, remarkably high‐power conversion efficiency of 7.1% is achieved along with enhanced current density in P(NDI3‐T)‐based all‐PSCs, which is mainly attributed to red‐shifted light absorption and enhanced electron‐transporting ability.
The branching point of side chain in naphthalenediimide (NDI)‐based polymers is systematically controlled. As the branching point shifts away from the backbone, the well‐ordered intermolecular assembly with bimodal orientations evolves, resulting in a red‐shifted absorption and a higher electron mobility. All‐polymer solar cells (all‐PSCs) benefit from these changes by achieving a power conversion efficiency of 7.1%.
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