Mapping Visual Attributes of Logos: A Case Study of Parallel Coordinate Plots (EuroVis 2015)

<p>This paper uses visualization technique on graphical features of logos as a different way to approach creating or studying logo designs. We gathered 720 logos from the website, logolounge.com, and identified 9 features and 55 feature attributes through a full-script open coding analysis. Identified features were mapped using Parallel Coordinates Plot, with which users could analyze and compare logo designs. This visualization process might contribute to any designers or researchers who are looking for ways to study historical trend or visual attributes of logos.</p

Comparative Study of Thermal Stability, Morphology, and Performance of All-Polymer, Fullerene–Polymer, and Ternary Blend Solar Cells Based on the Same Polymer Donor

We compared the thermal and morphological stability of all-polymer solar cells (all-PSCs) and fullerene-based PSCs (fullerene-PSCs) having the same polymer donor (PBDTTTPD), which provided comparable peak power conversion efficiencies (PCEs) of >6%. We observed a remarkable contrast in thermal stability dependent upon the acceptor composition in the active layer, with the performance of the fullerene-PSCs completely deteriorating after annealing for 5 h at 150 °C, whereas that of the all-PSCs remained stable even after annealing for 50 h at 150 °C. Pronounced phase separation was observed in the active layer of the fullerene-PSCs at two different length scales. In stark contrast, almost no morphological changes in the all-PSCs were observed, likely due to the low diffusion kinetics of the polymer acceptors. To develop a comprehensive understanding of the role of polymer acceptor on the thermal stability of devices, the morphology of ternary blend active layers composed of PBDTTTPD:polymer acceptor:fullerene acceptor with different fullerene contents was examined while annealing at 150 °C. The ternary blends showed two extreme trends of all-PSC- and fullerene-PSC-like behavior in thermal stability depending on the PCBM content. When included in the active layer as <30 wt % of the acceptor mixture, fullerene was well-dispersed in the amorphous portion of the donor/acceptor polymer blend under thermal stress and led to thermally stable devices with a higher PCE (7.12%) than both all-PSCs without fullerene (6.67%) and polymer–fullerene active layers without a polymeric acceptor (6.12%)

Charge Generation Dynamics in Efficient All-Polymer Solar Cells: Influence of Polymer Packing and Morphology

All-polymer solar cells exhibit rapid progress in power conversion efficiency (PCE) from 2 to 7.7% over the past few years. While this improvement is primarily attributed to efficient charge transport and balanced mobility between the carriers, not much is known about the charge generation dynamics in these systems. Here we measured exciton relaxation and charge separation dynamics using ultrafast spectroscopy in polymer/polymer blends with different molecular packing and morphology. These measurements indicate that preferential face-on configuration with intermixed nanomorphology increases the charge generation efficiency. In fact, there is a direct quantitative correlation between the free charge population in the ultrafast time scales and the external quantum efficiency, suggesting not only the transport but also charge generation is key for the design of high performance all polymer solar cells

Importance of Optimal Composition in Random Terpolymer-Based Polymer Solar Cells

A new series of donor–acceptor (D–A) conjugated random terpolymers (PBDTT–DPP–TPD) were synthesized from electron-rich thienyl-substituted benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene (BDTT), in conjugation with two electron-deficient units, pyrrolo­[3,4-<i>c</i>]­pyrrole-1,4-dione (DPP) and thieno­[3,4-<i>c</i>]­pyrrole-4,6-dione (TPD), of different electron-withdrawing strengths. The optical properties of these random terpolymers can be easily controlled by tuning the ratio between DPP and TPD; an increase in TPD induced increased absorption between 400 and 650 nm and a lower highest occupied molecular orbital energy level, while higher DPP contents resulted in stronger absorption between 600 and 900 nm. The best power conversion efficiency (PCE) of 6.33% was obtained from PBDTT–DPP75–TPD25 with [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) due to the improved light absorption and thus a short-circuit current density (<i>J</i>_SC) higher than 16 mA/cm². Interestingly, the trend observed in the PCE values differed from that of optical behavior of the PBDTT–DPP–TPD in terms of the DPP to TPD ratio, showing nonlinear compositional dependence from 2 to 6%. Density functional theory calculations showed that the small portions of strong electron-withdrawing DPP in PBDTT–DPP25–TPD75 and PBDTT–DPP10–TPD90 could provide trap sites, which suppress efficient charge transfer. In contrast, for PBDTT–DPP90–TPD10 and PBDTT–DPP75–TPD25, the effect of minor portions of TPD on electron density distribution was found to be minimal. In addition, the polymer packing and nanomorphology were investigated by grazing-incidence X-ray scattering and atomic force microscopy. The findings suggested that controlling the ratio of electron-deficient units in the random terpolymers is critical for optimizing their performance in polymer solar cells because it affects the polymer packing structure, the optical and electrical properties, and the electron distribution in the polymers

Ethanol-Processable, Highly Crystalline Conjugated Polymers for Eco-Friendly Fabrication of Organic Transistors and Solar Cells

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 <i>π–π</i> 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

Amorphous Thieno[3,2‑<i>b</i>]thiophene and Benzothiadiazole Based Copolymers for Organic Photovoltaics

Three types of amorphous thienothiophene (TT)-benzothiadiazole (BT) based copolymers (<b>PFTTBT</b>) were synthesized by incorporating alkyl-substituted fluorene moieties as a third component in the polymer backbone. Their optical, electrochemical, morphological, and photovoltaic properties were examined by a comparison with those of a crystalline TT-BT derivative (<b>PTTBT14</b>). <b>PTTBT14</b> was reported to have a high hole mobility (0.26 cm²/(V s)) due to the pronounced interchain ordering but poor photovoltaic power conversion efficiency (PCE) of 2.4–2.6% was reported due to excessively strong self-interactions with poor miscibility with fullerene structures. By incorporating fluorene units, the UV–vis spectra showed an increased bandgap (∼1.9 eV) with the disappearance of the packing-originated shoulder peak, and the valence band decreased compared to crystalline <b>PTTBT14</b>. The amorphous <b>PFTTBT</b> polymers showed substantially improved photovoltaic properties compared to <b>PTTBT14</b>, even though they showed poor hole mobility (∼10^–6 cm²/(V s)) and fill factor. The optimal devices were achieved by blending with excess PC₇₁BM (polymer:PC₇₁BM = 1:4 by weight), showing little improvement in the thermal and additive treatments. Under simulated solar illumination of AM 1.5 G, the best PCE of 6.6% was achieved for a <b>PFehTTBT</b>:PC₇₁BM device with an open-circuit voltage of 0.92 V, a short-circuit current of 15.1 mA/cm², and a fill factor of 0.48. These results suggest that it is useful to disrupt partially the interchain organizations of excessively crystalline polymers, enabling fine-control of intermolecular ordering and the morphological properties (i.e., miscibility with fullerene derivatives, etc.) to utilize the advantages of both crystalline and amorphous materials for further improving PCE of polymer solar cells

Correlation between Phase-Separated Domain Sizes of Active Layer and Photovoltaic Performances in All-Polymer Solar Cells

The control of the bulk-heterojunction (BHJ) morphology in polymer/polymer blends remains a critical hurdle for optimizing all-polymer solar cells (all-PSCs). The relationship between donor/acceptor phase separation, domain size, and the resulting photovoltaic characteristics of PDFQx3T and P­(NDI2OD-T2)-based all-PSCs was investigated. We varied the film-processing solvents (chloroform, chlorobenzene, <i>o</i>-dichloro­benzene, and <i>p</i>-xylene), thereby manipulating the phase separation of all-polymer blends with the domain size in the range of 30–300 nm. The different volatility and solubility of the solvents strongly influenced the aggregation of the polymers and the BHJ morphology of polymer blends. Domain sizes of all-polymer blends were closely correlated with the short-circuit current density (<i>J</i>_SC) of the devices, while the open-circuit voltage (0.80 V) and fill factor (0.60) were unaffected. All-PSCs with the smallest domain size of ∼30 nm in the active layer (using chloroform), which is commensurate with the domain size of highly efficient polymer/fullerene solar cells, had the highest <i>J</i>_SC and power conversion efficiency of 5.11% due to large interfacial areas and efficient exciton separation. Our results suggest that the BHJ morphology was not fully optimized for most of the previous high-performance all-PSC systems, and their photovoltaic performance can be further improved by fine-engineering the film morphology, i.e., domain size, domain purity, and polymer packing structure

Highly Efficient Red-Emitting Hybrid Polymer Light-Emitting Diodes via Förster Resonance Energy Transfer Based on Homogeneous Polymer Blends with the Same Polyfluorene Backbone

Highly efficient inverted-type red-emitting hybrid polymeric light-emitting diodes (HyPLEDs) were successfully demonstrated via Förster resonance energy transfer (FRET) and interfacial engineering of metal oxide with a cationic conjugated polyelectrolyte (CPE). Similarly structured green- and red-emissive polyfluorene copolymers, F8BT and F8TBT, were homogeneously blended as a FRET donor (host) and acceptor (dopant). A cationic polyfluorene-based CPE was also used as an interfacial layer for optimizing the charge injection/transport and improving the contact problem between the hydrophilic ZnO and hydrophobic polymer layer. A long Förster radius (<i>R</i>₀ = 5.32 nm) and high FRET efficiency (∼80%) was calculated due to the almost-perfect spectral overlap between the emission of F8BT and the absorption of F8TBT. A HyPLED containing 2 wt % F8TBT showed a pure red emission (λ_max = 640 nm) with a CIE coordinate of (0.62, 0.38), a maximum luminance of 26 400 cd/m² (at 12.8 V), a luminous efficiency of 7.14 cd/A (at 12.8 V), and a power efficiency of 1.75 lm/W (at 12.8 V). Our FRET-based HyPLED realized the one of the highest luminous efficiency values for pure red-emitting fluorescent polymeric light-emitting diodes reported so far

Gadolinium Complex of ¹²⁵I/¹²⁷I‑RGD-DOTA Conjugate as a Tumor-Targeting SPECT/MR Bimodal Imaging Probe

The work describes the synthesis and in vivo application of [Gd­(L)­(H₂O)]·<i>x</i>H₂O, where L is a (¹²⁵I/¹²⁷I-RGD)- DOTA conjugate, as a tumor-targeting SPECT/MR bimodal imaging probe. Here, (¹²⁵I/¹²⁷I-RGD)-DOTA signifies a “cocktail mixture” of radioisotopic (<b>1a</b>, L = ¹²⁵I-RGD-DOTA) and natural (<b>1b</b>, L = ¹²⁷I-RGD-DOTA) Gd complexes. The two complexes are chemically equivalent as revealed by HPLC, and their cocktail mixture exhibits the integrin-specific tumor enhancement, demonstrating that they constitute essentially a single bimodal imaging probe. Employment of a cocktail mixture thus proves to be a sole and practical approach to overcome the sensitivity difference problem between MRI and SPECT

Heteronuclear Gd-^99mTc Complex of DTPA-Bis(histidylamide) Conjugate as a Bimodal MR/SPECT Imaging Probe

The work describes the synthesis and in vivo application of heterotrimetallic complexes of the type {Gd­(H₂O)­[(M­(H₂O)­(CO)₃)₂(<b>1</b>)]} {<b>1</b> = DTPA-bis­(histidyl-amide); <i>M</i> = Re (<b>3a</b>); ^99mTc (<b>3b</b>)} for dual modality MR/SPECT imaging. Here, the DTPA-bis­(histidylamide) conjugate functions as a trinucleating chelate incorporating Gd in the DTPA core with Re or ^99mTc in the pair of histidylamide side arms. The two complexes are chemically equivalent as revealed by HPLC, and their “cocktail mixture” (<b>3a</b> + <b>3b</b>) has demonstrated itself to be essentially a single bimodal imaging probe. The present system has thus overcome the sensitivity difference problem between MRI and SPECT and paved the way for practical applications