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A radon monitoring system capable of continuous real-time monitoring of well gas radon was devised and tested in a climate change observation network. It comprised a radon detector and could help observe the groundwater in a well, blocking the inflow of outside air. The water temperature, electrical conductivity, and water level were also monitored in the groundwater well. The temperature and electrical conductivity were almost constant within a 1% error range in both the 5-day preliminary and the 7-month long-term tests. The groundwater level appeared to be related to radon concentration, and tidal forces may have influenced both radon concentration and groundwater levels.

A simple wet-chemical route for the preparation of core-shell-structured catalysts was developed to achieve high oxygen reduction reaction (ORR) activity with a low Pt loading amount. Nickel nitride (Ni3N) nanoparticles were used as earth-abundant metal-based cores to support thin Pt layers. To realize the site-selective formation of Pt layers on the Ni3N core, hydrogen molecules (H2) were used as a mild reducing agent. As H2 oxidation is catalyzed by the surface of Ni3N, the redox reaction between H2 and Pt(IV) in solution was facilitated on the Ni3N surface, which resulted in the selective deposition of Pt on Ni3N. The controlled Pt formation led to a subnanometer (0.5-1 nm)-thick Pt shell on the Ni3N core. By adopting the core-shell structure, higher ORR activity than the commercial Pt/C was achieved. Electrochemical measurements showed that the thin Pt layer on Ni3N nanoparticle exhibits 5 times higher mass activity and specific activity than that of commercial Pt/C. Furthermore, it is expected that the proposed simple wet-chemical method can be utilized to prepare various transition-metal-based core-shell nanocatalysts for a wide range of energy conversion reactions.

One of the main drawbacks of tungsten trioxide (WO3) electrochromic materials is slow response time due to the low electrical conductivity of WO3. In this work, a silver nanowire (AgNW)-embedded WO3 composite structure was designed to improve electrochromic performance. The AgNW-embedded WO3 electrochromic thin films were fabricated by an electrodeposition method. In addition to phase and morphology analyses, electrochromic performance was evaluated via an examination of transmittance modulation, response time, and coloration efficiency. The electrochromic study reveals that embedding AgNWs into the WO3 has a significant impact on electrochromic performance. Due to the presence of a percolated AgNW network with high electrical conductivity and surface roughness, the AgNW-embedded WO3 thin films exhibit faster Li-ion intercalation/de-intercalation kinetics (coloration time of 12 s and bleaching time of 2 s) and a greater coloration efficiency (45.3 cm2/C) with better cyclic stability than a single-layer WO3 thin film. Such results indicate AgNW-embedded WO3 electrochromic thin films as attractive for practical application of electrochromic devices in energy-saving smart windows.

Full utilization of electrodes toward high-performance energy storage is challenging in cases where electrode/electrolyte interface is significant. From a practical perspective, this is particularly important in cases where a thick electrode or one with a high mass loading is needed. Here, we report an approach to increase the electrode performance by the infilling of a highly ion-conductive organic gel polymer electrolyte (EI-GPE, ionic conductivity ∼9.2 mS cm−1) into a multi-walled carbon nanotube (MWCNT) electrode with high mass loadings of up to 26 mg cm−2 (or significant thicknesses of up to 443 μm). Typical GPE (t-GPE) with a film-forming property but moderate ionic conductivity (1.2 mS cm−1) is then placed over the EI-GPE-filled electrode surface, resulted in flexible supercapacitor. Infilling of EI-GPE into MWCNT electrode provides a large-ion accessible interface that affords the increase in volumetric capacitance and energy density, about sixfold greater than that of the typical supercapacitors configured by sandwiching t-GPE as both electrolyte and the separator between a pair of electrodes. Importantly, this method enables scaling of the areal capacitance with electrode thickness (or mass loading of active material). A pouch type EI-SC provides stable performance after bending, suggesting it holds the promise of flexible energy storage.

We demonstrate that control of the defect level on carbon materials is effective for enhancing the oxygen reduction reaction (ORR) performance of nonprecious-metal catalysts. Vapor-grown carbon nanofiber (VGCNF) with high crystallinity and high electronic conductivity was chosen as the substrate of our ORR catalysts. To induce defects on the VGCNF, it was subjected to ball-milling for various controlled times, yielding BMx-VGCNF (x represents the ball-milling time, 0-6 h). The defect level introduced on the VGCNF was effectively regulated by controlling the ball-milling time. Although the density of defect sites increased with increasing ball-milling time, the surface area was high-est in BM2-VGCNF. Nonprecious-metal ORR catalysts (BMx-Fe-VGCNF) were prepared by NH3 pyrolysis of Fe-ion-adsorbed BMx-VGCNF. The ball-milling of VGCNF was effective to introduce nitrogen onto the catalyst. In particular, the controlled ball-milling was important to generate highly active sites on the catalyst surface. Among the catalysts studied, BM2-Fe-VGCNF exhibited the best ORR performance, which was 2.5-times greater than that of BMx-Fe-VGCNF (x=4, 6).

We present design and synthesis of three new symmetrical and linear A-D-A type π-conjugated donor small molecules (2D-NDT(TPD)2, 2D-NDT(Ester)2 and 2D-NDT(Amide)2) containing two dimensional (2D) naphthodithiophene (NDT) unit as the central donor core, end-capped with electron deficient unit such as thieno[3,4c]pyrrole-4,6-dione (TPD), 2-ethylhexyl 2-cyanoacetate (Ester) and 2-cyano-N-(2-ethylhexyl)acetamide (Amide) group respectively. We characterized these small molecules and further investigated the optical, electrochemical, morphological and photovoltaic properties. When solution–processed bulk heterojunction organic solar cells are fabricated using these small molecules, the morphology of 2D-NDT(Ester)2 or 2D-NDT(Amide)2 and [6,6]-PhenylC71-butyric acid methyl ester (PC71BM) blend film was optimized using 1,8 Diiodooctane (DIO) additive. DIO additive promotes the formation of nanoscopically well-connected molecular domains in the active blend film. A device based on (1% DIO, 1:1) 2D-NDT(Ester)2:PC71BM exhibited highest the efficiency of 1.22% with a short-circuit density (Jsc) of 3.75 mA/cm2, an open circuit voltage (Voc) of 0.91 V and fill factor (FF) of 35.50. Similarly for (1% DIO, 1:3) 2D-NDT(Amide)2:PC71BM device efficiency of 0.55%, with Jsc of 2.36 mA/cm2, Voc of 0.64 V and FF of 36.95 was observed. Whereas for (1:2) 2D-NDT(TPD)2:PC71BM device, due to the improper blending and phase separation between donor and acceptor efficiency restricted to 0.33% with Jsc of 1.66 mA/cm2, Voc of 0.73 V and FF of 27.2.

Here, we prepare a bimetallic CuFe–N–C catalyst for the oxygen reduction reaction (ORR) by annealing metal precursor-adsorbed polyaniline under an NH3 gas atmosphere at high temperature. The catalyst exhibits higher ORR activity and durability than Pt/C and other monometallic Cu (Fe)–N–C catalysts in 0.1 M KOH. The remarkable catalytic activity of the CuFe–N–C catalyst is due to the interaction between Cu and Fe, which facilitates ORR and also results in higher contents of total N and active N species. In the same vein, single cell using the CuFe–N–C catalyst exhibits greatly enhanced performance compared to those using other catalysts.

The possibility of exchange reactions and thermal self-healing in blends of thermoplastic polyurethane (TPU) and phenoxy resin was investigated herein. The analyses were based on characterization obtained via differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and tensile test. A new phenoxy resin was synthesized from eugenol, and blends with different types of TPU were prepared to investigate the exchange reaction, thermal self-healing, and mechanical properties. The influence of phenoxy resin content on the mechanical behavior and healing efficiency was studied. Improvement of storage modulus owing to the increase of phenoxy resin content was observed. Results suggest that the exchange reaction between phenoxy- and ester-type TPU occurred during thermal treatment. However, little exchange occurred between phenoxy resin and ether-type TPU. Specifically, only ester-type TPU exhibited a significant exchange reaction in the phenoxy resin blend. Furthermore, in the presence of a catalyst (e.g., zinc acetate), the exchange reaction readily occurred, and the healing efficiency improved by the addition of the catalyst and increase in the phenoxy content.

Galvanic displacement reaction has been considered a simple method for fabricating hollow nanoparticles. However, the formation of hollow interiors in nanoparticles is not easily achieved owing to the easy oxidization of transition metals, which results in mixed morphologies, and the presence of surfactants on the nanoparticle surface, which severely deteriorates the catalytic activity. In this study, we developed a facile gram-scale methodology for the one-pot preparation of carbon-supported PtNi hollow nanoparticles as an efficient and durable oxygen reduction electrocatalyst without using stabilizing agents or additional processes. The hollow structures were evolved from sacrificial Ni nanoparticles via an in situ galvanic displacement reaction with a Pt precursor, directly following a preannealing process. By sampling the PtNi/C hollow nanoparticles at various reaction times, the structural formation mechanism was investigated using transmission electron microscopy with energy-dispersive X-ray spectroscopy mapping/line-scan profiling. We found out that the structure and morphology of the PtNi hollow nanoparticles were controlled by the acidity of the metal precursor solution and the nanoparticle core size. The synthesized PtNi hollow nanoparticles acted as an oxygen reduction electrocatalyst, with a catalytic activity superior to that of a commercial Pt catalyst. Even after 10 000 cycles of harsh accelerated durability testing, the PtNi/C hollow electrocatalyst showed high performance and durability. We concluded that the Pt-rich layers on the PtNi hollow nanoparticles improved the catalytic activity and durability considerably.

We report for the first time that alkali carbonates (Li2CO3, K2CO3, and Rb2CO3) based on a low-temperature solution process can be used as interfacial modifiers for SnO2 as robust electron-transport layers (ETL) for inverted organic solar cells (iOSCs). The room-temperature photoluminescence, the electron-only devices, and the impedance studies altogether suggested the interfacial properties of the alkali carbonates–modified SnO2 ETLs, which were much better than those based on the SnO2 only, provided efficient charge transport, and reduced the charge recombination rates for iOSCs. The iOSCs using the polymer donor poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] and the fullerene acceptor phenyl-C70-butyric acid methyl ester as the active layer showed the average power-conversion efficiencies (PCEs) based on ten devices of 6.70, 6.85, and 7.35% with Li2CO3-, K2CO3-, and Rb2CO3-modified SnO2 as...

Biomass is a useful precursor for manufacturing electrocatalysts because it is highly abundant, eco-friendly, and is composed of organic materials that include Fe and nitrogen precursors. Among the numerous waste biomass types, slaughtered pig blood contains a high concentration of Fe-porphyrin inside the hemoglobin, and this characteristic makes it an ideal precursor for fabricating a bio-inspired Fe-N-C oxygen reduction reaction (ORR) catalyst. Here, Zinc (Zn)-hydrolysates are obtained from purified waste pig blood was used as a porous carbon source for two-dimensional (2D) sheet-like porous single-atom electrocatalysts. In addition, pig blood provides Fe single-atom catalytic sites derived from hemoglobin in (Zn)-hydrolysates and shows excellent ORR activity by retaining excellent mass transfer due to the presence of mesopores generated by Zn activation under NH3 pyrolysis Furthermore, one of the catalytic materials is a Zn-incorporated Fe single-atom porous carbon catalyst (designated Zn/FeSA-PC)/950/NH3, was successfully integrated as an Anion Exchange Membrane Fuel Cells (AEMFCs) and Zn‐Air Batteries (ZABs) where it supported maximum power densities of 352 and 220 mW/cm2, respectively. This study demonstrates the new designs and preparation procedures for high-performance electrocatalysts that can be manufactured at low cost from abundant and renewable blood biomass.

With limited biomass that can be currently utilized as a renewable resource, it is important to develop a method to convert biomass into materials that can replace fossil fuel product. In this paper, eugenol, a bio-based allyl chain-substituted guaiacol, was used to synthesize self-healable copolymers. Eugenol terminated polyurethane prepolymer (ETPU) was synthesized from eugenol and polyurethane prepolymers terminated with isocyanate groups. ETPU contained two allyl groups. Self-healing copolymer networks were obtained by copolymerization of ETPU and styrene monomer via free radical polymerization. Effects of ETPU content on the properties of copolymers were then studied. These copolymers containing ETPU exhibited good thermal stability and mechanical properties. These copolymers showed higher tensile strength and elongation at break than PS. Their maximum tensile strength reached 19 MPa. In addition, these copolymers showed self-healing property at elevated temperature due to the reversible nature of urethane units in ETPU.

Tin oxide (SnO2) has been widely accepted as an effective electron transport layer (ETL) for optoelectronic devices because of its outstanding electro-optical properties such as its suitable band energy levels, high electron mobility, and high transparency. Here, we report a simple but effective interfacial engineering strategy to achieve highly efficient and stable inverted organic solar cells (iOSCs) via a low-temperature solution process and an SnO2 ETL modified by zwitterion nondetergent sulfobetaine 3-(4-tert-butyl-1-pyridinio)-1-propanesulfonate (NDSB-256-4T). We found that NDSB-256-4T helps reduce the work function of SnO2, resulting in more efficient electron extraction and transport to the cathode of iOSCs. NDSB-256-4T also passivates the defects in SnO2, which serves as recombination centers that greatly reduce the device performance of iOSCs. In addition, NDSB-256-4T provides the better interfacial contact between SnO2 and the active layer. Thus, a higher power conversion efficiency (PCE) and longer device stability of iOSCs are expected for a combination of SnO2 and NDSB-256-4T than for devices based on SnO2 only. With these enhanced interfacial properties, P3HT:PC60BM-based iOSCs using SnO2/NDSB-256-4T (0.2 mg/mL) as an ETL showed both a higher average PCE of 3.72%, which is 33% higher than devices using SnO2 only (2.79%) and excellent device stability (over 90% of the initial PCE remained after storing 5 weeks in ambient air without encapsulation). In an extended application of the PTB7-Th:PC70BM systems, we achieved an impressive average PCE of 8.22% with SnO2/NDSB-256-4T (0.2 mg/mL) as the ETL, while devices based on SnO2 exhibited an average PCE of only 4.45%. Thus, the use of zwitterion to modify SnO2 ETL is a promising way to obtain both highly efficient and stable iOSCs.

Biomass derived carbon via hydrothermal carbonization are critically important for the catalysis research field requiring high activity with low cost. However, most of them present low activity due to low surface areas with large particle size originating from unnecessary compounds in raw status. Here, we report a porous carbon decorated with Fe3C/Fe3O4 nanoparticles via pretreatment of pig blood (PB) by employing solvent pretreatment and pyrolyzing in regulated environment using a Fe-porphyrin-type macrocycle as catalyst precursors. Importantly, the addition of toluene to the raw form of PB as pretreatment plays a significant role in not only producing the nanoparticles with porous carbon materials but also removing impurities that deteriorate the active sites of molecular nitrogen carbon (MNC) type catalysts during high-temperature activation. Furthermore, the temperature for hydrothermal treatment and pyrolysis influences oxygen reduction reaction (ORR) performances. The highest-performing PB-derived catalyst delivered its kinetic current and the degree of degradation (after 10,000 potential cycles) were 1.57 mA/cm2 (at 0.9 V) and 19 mV (half-wave potential), and those of Pt/C were 1.26 mA/cm2 and 43 mV, respectively. The catalysts were prepared by applying pretreatment to the PB and characterized systematically to investigate how such pretreatment influences the physical properties and ORR performances.

1-D ZnO represents a fascinating class of nanostructures that are significant to optoelectronics. In this work, we investigated the use of an eco-friendly, metal free in situ doping through a pure thiophene-sulfur (S) on low temperature processed (

The issue of work-function and surface energy is fundamental to ‘decode’ the critical inorganic/ organic interface in hybrid organic photovoltaics, which influences important photovoltaic events like exciton dissociation, charge transfer, photocurrent (Jsc), open circuit voltage (Voc), etc. We demonstrate that by incorporating an interlayer of cyanoacrylic acid on solution processed, spin-coated, planar ZnO NRs, higher photovoltaic (PV) performances were achieved in both inverted organic photovoltaic (iOPV) and hybrid organic photovoltaic (HOPV) devices, where ZnO acts as an “electron transporting layer” and as an “electron acceptor”, respectively. For the tuned range of surface energy from 52.5 mN/m to 33 mN/m, the power conversion efficiency (PCE) in bulk heterojunction (BHJ) iOPVs based on poly(3-hexylthiophene) (P3HT) and phenyl-C60-butyric acid methyl ester (PC60BM) increases from 3.16% to 3.68% and that based on Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5b']dithiophene-2,6-diyl-alt-(4...

Four BDT-TPD polymers (PA–PD) were synthesized by modifying the alkylthienyl chains on BDT, placing spacer group between BDT and TPD, and installing extended conjugated side chains on the BDT of the polymer to investigate the correlation between structure and photovoltaic performance for these polymers. The molecular weight of PA–PD polymers ranged from the highest (Mn = 80 kDa for PA) to the lowest (Mn = 7.9 kDa for PD), and their decomposition temperatures at 5% weight loss were in the range 401–435 °C. PA, PB, and PC showed similar UV–vis absorption spectra; however, PD showed much broader absorption spectrum in the entire UV–vis region, because of the extended conjugated side chains. The HOMO levels of the polymers were −5.72, −5.63, −5.48, and −5.61 eV for PA, PB, PC, and PD, respectively, indicating very low-lying HOMO energy levels. The bandgaps of these polymers were calculated and found to be in the range 1.85–1.88 eV. The theoretical calculations clearly show that the torsional angles between the alkylthienyl group and BDT unit of the simplified dimer correlated to the π-orbital delocalization, suggesting that the HOMO π-electrons of vertically aligned conjugated side chains do not delocalize well in the polymers such as PA, PB, and PC bearing high torsional angles. The optimized weight ratios of the polymer to PC61BM were determined to be 1:1, 1:1.5, and 1:1 for PA, PC, and PD, respectively, and the average PCEs of the devices were 5.36%, 4.62%, and 2.74% for PA, PC, and PD, respectively, after optimization with 1,8-diiodooctane (DIO). A relatively small amount of DIO as an additive was necessary to reach the optimal PCEs of the devices, and the device incorporating PC needed only 0.5% DIO to obtain the best PCE. The AFM study reveals that the blend films after adding DIO showed much smooth morphologies, and the blend film of PA exhibited more crystalline property, as shown by the XRD analysis.

6,6′-Dibromo- N,N ′-(2-octyldodecanyl)isoindigo was coupled to either 4-( N -carbazolyl)phenyl boronic acid or 9-phenyl-9H-carbazole-3-boronic acid to give two different conjugated molecules of P-II-P and C-II-C, respectively. The optical band gap/HOMO levels of P-II-P and C-II-C were 1.90/−5.60 eV and 1.85/−5.39 eV, respectively. Based on the experimental and calculation data, C-II-C is more highly conjugated than P-II-P. The performances of C-II-C-based photovoltaic devices were better than those of P-II-P-based devices, with the best power conversion efficiency of 0.44%.

Two π-conjugated small molecules, BDT(TTBT)2 and BDT(PTBT)2, based on benzodithiophene (BDT) and benzothiadiazole (BT) substituted with different terminal groups such as hexyl-bithiophene and hexylphenyl-thiophene are investigated for use in solution-processed organic solar cells (OSCs). Investigations into the molecules reveal that variation of the terminal groups not only influences the optical and electronic properties, but also affects the crystallization and morphology of the small molecules. The BDT(TTBT)2 device showed a power conversion efficiency (PCE) of 1.73% as a consequence of deep HOMO (Voc = 0.81 V), improved charge delocalization, and strong light absorption (Jsc = 4.75 mA cm−2) when mild annealing was used as a result of improved texture in morphology, while the BDT(PTBT)2 device rather showed a moderate PCE of 1.22% with a Jsc of 2.88 mA cm−2, a Voc of 0.81 V, and a FF of 0.52.

Here we report functionalized multiwalled carbon nanotubes (f-MWCNTs)-CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where f-MWCNTs were uniformly coated with CdSe NCs onto SnO2 upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern-Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO2-CdSe photoanode. Atomic and weight percent changes of carbon with f-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over f-MWCNTs forming a core-shell type structure as a blend. Compared to pristine CdSe, photoanode with f-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO2-f-MWCNTs-blend-CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10(-4) to 10.89 × 10(-4) cm(2) V(-1) S(1-)), (b) diffusion length (27 × 10(-6))

A conjugated polymer consisting of alternating octyldodecyldiketopyrrolo[3,4-c]pyrrole (DPP) and diethoxynaphthalene (EN) units (PDPP-TENT) with thiophene (T) spacers, was synthesized ( M n 19 000), which showed a typical absorption of conjugated polymers ( λ max = 720 nm, solid state). Based on the calculated geometry, PDPP-TENT is only slightly bent (170°) and extensively conjugated. The optical band gap and highest occupied molecular orbital (HOMO) level of the polymer were determined to be 1.61 eV and −5.46 eV, respectively. The polymer-based photovolatic devices (ITO/PED:PSS/PDPP-TENT:PC71BM:diiodooctane/LiF/Al) exhibited the power conversion efficiencies of up to 1.6%.

This study involves the development of two new small molecules comprising a diketopyrrolopyrrole (DPP) core flanked with donor units of triphenylamine (TPA-DPP-TPA) and fluorine (FL-DPP-FL) for application in bulk heterojunction (BHJ) organic solar cells (OSCs). The OSCs based on FL-DPP-FL and PC 71 BM exhibited a PCE of 1.73%, compared to 1.45% for that obtained from devices of TPA-DPP-TPA. The morphological studies reveal that the enhancement in OSCs of FL-DPP-FL is mainly attributed to the improved nanoscale film morphology of the FL-DPP-FL:PC 71 BM blend, which promoted the formation of smaller domains and greater donor–acceptor interpenetrated networks within the active layer.

Polydopamine can be formed and deposited on the surface of titanium substrates either by classical dip coating (d-pdopa) or by electropolymerization (e-pdopa), which has been recently developed. In contrast to the classical approach, dopamine electropolymerization leads to the formation of continuous, smooth films on the surface of the substrate. We further studied the applicability of the polydopamine films by examining their ability to spontaneously reduce silver ions into metal nanoparticles. A simple bacterial inhibition test was conducted with Escherichia coli and Staphylococcus aureus bacteria to examine the differences in the antibacterial efficiency of both e-pdopa and d-pdopa films coated with silver nanoparticles. The e-pdopa samples contained clearer inhibition zones than the d-pdopa samples, which is indicative of the silver nanoparticles being immobilized on e-pdopa film in a more efficient manner for the antimicrobial functionalization of metal implants.

We herein report an investigation of aqueous solution-processable molybdenum-oxide (MoO3) hole-selective layers fabricated for solution-processable organic semiconducting devices. A homogeneous MoO3 layer was successfully deposited via spin-coating using aqueous solutions of ammonium heptamolybdate as a MoO3 precursor. The use of the solution-processable MoO3 layer as a hole-injecting layer (HIL) on an indium-tin-oxide (ITO) anode in solution-processable organic light-emitting diodes (OLEDs) resulted in excellent device performance in terms of the brightness (maximum brightness of 37,000 cd m−2) and the efficiency (peak efficiency of 25.2 cd A−1), comparable to or better than those of a reference OLED with a conventional poly(ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS) HIL. Such good device performance is attributed to the water-processable MoO3 hole-selective layers, which allowed the formation of a high-quality film and provided good matching of the energy levels between adjacent layers with improved hole-injecting properties, impedance characteristics, and stability. Furthermore, polymer solar cells (PSCs) with a MoO3 layer used as a hole-collecting layer (HCL) showed improved power conversion efficiency (3.81%), which was higher than that obtained using the PEDOT:PSS HCL. These results clearly indicate the benefits of using a water-processable MoO3 layer, which effectively acts as a hole-selective layer on an ITO anode and provides good hole-injection/collection, electron-blocking and energy-level-matching properties, and improved stability. They, therefore, offer considerable promise as an alternative to a conventional PEDOT:PSS layer in the production of high-performance solution-processable organic semiconducting devices.

An isoindigo-dithienocarbazole-isoindigo oligomer (II-DTC-II) was synthesized by a Stille coupling reaction between N -hexadecyl-2,8-bis(trimethylstannyl)dithieno[3,2-b:6,7-b]carbazole and 6-bromo- N , N ′-dioctylisoindigo. The oligomer exhibited a broad absorption with an optical band gap of 1.75 eV and a highest occupied molecular orbital energy level of −5.46 eV. Photovoltaic devices were fabricated using the II-DTC-II oligomer and [6,6]-phenyl C 71 butyric acid methyl ester (PC 71 BM), to obtain the configuration ITO/PEDOT:PSS/II-DTC-II:PC 71 BM/LiF/Al. The best power conversion efficiency of the II-DTC-II-based devices was 1.13% when 0.8 wt% diiodooctane was mixed into the active layer of II-DTC-II/PC 71 BM (1:1). The low conversion efficiency was attributed to the oligomer's poor solubility and miscibility with PC 71 BM.

Two new small molecules, based on diketopyrrolopyrrole core flanked by cyanothiophene units (CN-DPP-CN, CN-TH-DPP-TH-CN) were synthesized using CuCN and palladium catalyzed Suzuki coupling and explored in organic solar cells (OSCs). The HOMO/LUMO energy levels of CN-DPP-CN, CN-TH-DPP-TH-CN having moderate band gap of 1.83 eV and 1.44 eV were estimated to be −5.63/−3.84 eV, −5.20/−3.75 eV respectively. The device efficiency was found to be 0.013, 0.21% for CN-DPP-CN, CN-TH-DPP-TH-CN respectively as donors for BHJ solar cells. When CN-DPP-CN (0.05%) was added in P3HT:PC60BM device, its PCE was enhanced to 2.45% from 2.08% signifying its ability to be used as potential n-type additive.

E-mail: yosklear@jbnu.ac.krReceived December 25, 2013, Accepted February 19, 2014Key Words : Phenothiazine, Isoindigo, Solar cells, P-type polymersIn recent years, polymer solar cells (PSCs) have received agreat deal of attention for their low cost, light weight,solution processing capability, and mechanical flexibility.

Donor–acceptor conjugated polymers, PDTTPDA and PDTTPDT, composed of new acenaphtho[1,2-c]thiophene or thiophene as electron donors and 1,3-dithien-2-yl-thieno[3,4-c]pyrrole-4,6-dione (DTTPD) as the electron acceptor were synthesized by a Stille cross-coupling reaction. These polymers combine interesting properties such as good solubility and excellent thermal stability. The weight-averaged molecular weights (Mw) of PDTTPDA and PDTTPDT were found to be 71,000 and 79,000 with polydispersity indices of 1.65 and 1.66, respectively. Photophysical studies revealed a low bandgap of 1.77 eV for PDTTPDA and 1.72 eV for PDTTPDT. The present study indicates that the combination of DTTPD and acenaphtho[1,2-c]thiophene building blocks can be a very effective way to lower the HOMO energy level and ultimately to enhance the Voc of polymer solar cells. The Voc reported here (up to 0.94 V) is one of the highest observed in polymer:PCBM bulk heterojunction devices, and a power conversion efficiency (PCE) of up to 3.28% was observed in the PDTTPDA devices.

Alternating donor-acceptor (D–A) π-conjugated copolymers, poly[2,7-bis(3-hexadecylthiophene-2-yl)naphtho[1,2-b:5,6-b′]dithiophene-5,5′-diyl-alt-5,8-bis(4-hexadecylthiophen-2-yl)-2,3-bis(4-(octyloxy)phenyl)quinoxaline-5,5′-diyl] (PTNDTT-QX-I) and poly[2,7-bis(3-hexadecylthiophene-2-yl)naphtho[1,2-b:5,6-b′]dithiophene-5,5′-diyl-alt-5,8-bis(thiophen-2-yl)-2,3-bis(3-(octyloxy)phenyl)quinoxaline-5,5′-diyl] (PTNDTT-QX2-II), were designed and synthesized based on the same thiophene-bridged naphtho[1,2-b:5,6-b′]dithiophene donor moiety, differing only at the quinoxaline acceptor counterpart by either additional electron-donating alkyl chain substitution in the thienyl ring attached to the quinoxaline base (in PTNDTT-QX-I) or a change in the location of the outward alkoxy side chain substituent of the phenyl rings (to the meta-position) adjoining the quinoxaline base (in PTNDTT-QX-II). The effect of alkyl chain positioning on the thermal, optical, and electrochemical properties, as well as field effect transistors and solar cell performances of the copolymers, were investigated and the results were compared with a previously published copolymer, PTNDTT-QX, which features a similar quinoxaline unit but is alkoxy substituted at the position para to its peripheral phenyl rings. Both polymers exhibited excellent thermal stability, with thermal decomposition temperatures over 400 °C. They absorbed light in the 300–700 nm range and exhibited optical band gaps of about 1.70 and 1.73 eV for PTNDTT-QX-I and PTNDTT-QX-II, respectively. Precise control of the alkyl/alkoxy chain positioning has made it possible to tune the HOMO energy levels between −5.14 and −5.29 eV and the LUMO energy levels between −3.44 and −3.55 eV. Bulk heterojunction photovoltaic devices of the structure ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al were fabricated by using the polymers as the donors and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as the acceptor. Power conversion efficiencies (PCEs) of 1.28% and 1.61% respectively were achieved for the photovoltaic devices based on PTNDTT-QX-I/PC71BM and PTNDTT-QX-II/PC71BM under AM 1.5 G simulated 1-sun solar illumination.

Various rutile TiO2 nanostructures were grown using a wet chemical deposition method within plastic, glass, stainless-steel, copper, silver, etc., containers and their application in DSSCs was envisaged for the first time. The reaction rate is different in different containers. The effect of container environment on the morphology and optical properties of rutile TiO2 was investigated and can be attributed to the presence of the respective container element in TiO2. The metals (copper, silver, iron, sodium, etc.) are confirmed (in wt%) in the final products. Due to a change in the morphology followed by absorbance, the power conversion and incident photon-to-electron conversion efficiencies are different (higher in the copper container at 1.97% and 16%, and lower in the stainless-steel container at 0.26% and 3%, respectively). This change in performance can be attributed to a difference in the electron life time values, which are consistent with the charge transfer and series resistance values obtained from Nyquist plots.

A phenothiazine–diketopyrrolopyrrole polymer (PPT–DPP) with a thiophene spacer was synthesized with a number-average molecular weight of 17 600. The new polymer exhibited an optical band-gap of 1.63 eV and a highest occupied molecular orbital energy level of −5.20 eV. Photovoltaic devices were fabricated using the polymer and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) with the configuration ITO/PEDOT:PSS/PPT–DPP:PC71BM/LiF/Al. The polymer-based devices exhibited power conversion efficiencies as high as 1.8%. Based on atomic force microscopy data, the device performance was related to the morphology of the active layers.

Poly [3,3‴-didodecylquaterselenophene] (PQS) and poly[3,3‴-didodecylquaterselenophene-alt-didodecylquaterthiophene] (PQSQT), have been synthesized by using a Stille cross-coupling reaction. The weight-averaged molecular weights (Mw) of PQS and PQSQT were found to be 18,900 Da and 22,300 Da with polydispersity indices of 1.71 and 1.99, respectively. Photophysical measurements found the low bandgaps of 1.73 eV for PQS and 1.86 eV for PQSQT. The field-effect mobilities of PQS and PQSQT were determined to be 6.0×10−3 and 0.05 cm2/V s, respectively. The influence of the selenium and sulfur atoms in the polymer backbones were investigated with regard to device performances. The polymers were combined with the PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells with power conversion efficiencies of 0.73–2.37% under AM 1.5 G (100 mW/cm2) conditions.

Two conjugated polymers consisting of alternating dithieno[2,3- b ;7,6- b ]carbazole and thieno[3,4- c ]pyrrole-4,6-dione either without ( P1 ) or with ( P2 ) thiophene spacers were synthesized via Stille coupling. P1 and P2 showed a band gap of 2.07 and 1.80 eV and a highest occupied molecular orbital (HOMO) level of −5.2 and −5.1 eV, respectively. The P1 -based solar cells showed the best power conversion efficiency (PCE) of 2.51% when 1.0% diiodooctane was mixed into the active layer of P1 /PC 71 BM (1/1). In contrast, the PCE of P2 -based solar cells was much lower, due to its lower molecular weight, more curved backbone, smaller absorption coefficient, and slightly higher HOMO level.

Polymer solar cells (PSCs) have attracted considerable attention because of their unique advantages of low cost, light weight, and potential use in flexible devices. Based on the concept of a bulk heterojunction (BHJ) structure, PSCs made by blending poly(3-hexylthiophene) (P3HT) as a p-type material and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as an n-type material have been most intensively investigated and have shown power conversion efficiencies (PCEs) up to 5-6%. PCE of photovoltaic devices is proportional to the shortcircuit current density (Jsc), the open-circuit voltage (Voc), and the fill factor (FF). The Jsc of a solar cell is strongly affected by the absorption of the active layer, and thus an ideal p-type polymer should have a broad and strong absorption spectrum, which requires the polymer to have a low band-gap. The Voc is tightly related to the energy difference between the highest occupied molecular orbital (HOMO) of the p-type polymer and the lowest unoccupied molecular orbital (LUMO) of PCBM. Thus, the p-type polymer should have a low band-gap with appropriate energy levels of HOMO and LUMO. A facile method to synthesize low band-gap polymers is to combine electron-rich (electron-donor, D) and electrondeficient (electron-acceptor, A) monomers, forming alternating D-A type polymers. Quinoxaline was reported to be a good acceptor that can be combined with appropriate donors. For example, a thiophene-bis(3-octyloxyphenyl)quinoxaline polymer (TQ1) exhibited PCEs up to 6.0%. Alternating copolymers consisting of bis(3-alkoxyphenyl)quinoxaline and either dialkoxybenzene (LBPP) or fluorine (APFO) with a thiophene spacer showed PCEs up to 2.9% Another alternating copolymers of quinoxaline and either thieno[3,2-b]thiophene or carbazole with a thiophene spacer showed PCEs of 2.27% and 1.8%, respectively. A copolymer of 2,3-diphenylquinoxaline-based combined with a ladder type oligo-p-phenylene with a thiophene spacer showed a PCE of 3.04%. Some other types of quinoxaline-based copolymers with much lower PCEs were also reported. Poly(10-hexyl-10H-hexylphenothiazine-3,7-diyl) is a very strong electron donor and has a high ionization potential and has thus been used as a hole injection material in polymer light-emitting diodes. D-A type polymers consisting of phenothiazine and quinoxaline are also expected to be p-type materials with low band-gaps, but such polymers have not yet been reported in the literature. Thus, we attempted to synthesize a copolymer (PPTQX) consisting of alternating phenothiazine (PT) and dithienylquinoxaline (QX) segments for photovoltaic applications. As shown in Scheme 1, diboronic ester (compound 1) was reacted with dibromide (compound 2) in the presence of a palladium catalyst via Suzuki coupling to give the corresponding polymer, PPTQX. The polymer was purified using a Soxhlet extraction. The H NMR of the isolated polymer is shown in Figure 1, where the two different sets of aromatic protons (a, b) and four aliphatic protons (d) in the QX segment are easily identified along with two aliphatic protons (c) in the PT segment, indicating that PPTQX has been successfully synthesized. The numberand weight-average molecular weights of PPTQX were 7,000 and 12,000, respectively. The relatively low molecular weight of the polymer may be a result of the low reactivity of the QX monomer since its reacting sites are sterically hindered due to the two large alkoxyphenyl substituents. Molecular weights of LBPP and APFO, which were synthesized from QX monomers similar to ours, were also relatively low (Mn 12,000-15,000). 11

A set of three donor-acceptor conjugated (D-A) copolymers were designed and synthesized via Stille cross-coupling reactions with the aim of modulating the optical and electronic properties of a newly emerged naphtho[1,2-b:5,6-b′]dithiophene donor unit for polymer solar cell (PSCs) applications. The PTNDTT-BT, PTNDTT-BTz, and PTNDTT-DPP polymers incorporated naphtho[1,2-b:5,6-b′]dithiophene (NDT) as the donor and 2,2′-bithiazole (BTz), benzo[1,2,5]thiadiazole (BT), and pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP), as the acceptor units. A number of experimental techniques such as differential scanning calorimetry, thermogravimetry, UV–vis absorption spectroscopy, cyclic voltammetry, X-ray diffraction, and atomic force microscopy were used to determine the thermal, optical, electrochemical, and morphological properties of the copolymers. By introducing acceptors of varying electron withdrawing strengths, the optical band gaps of these copolymers were effectively tuned between 1.58 and 1.9 eV and their HOMO and LUMO energy levels were varied between −5.14 to −5.26 eV and −3.13 to −3.5 eV, respectively. The spin-coated polymer thin film exhibited p-channel field-effect transistor properties with hole mobilities of 2.73 × 10−3 to 7.9 × 10−5 cm2 V−1 s−1. Initial bulk-heterojunction PSCs fabricated using the copolymers as electron donor materials and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the acceptor resulted in power conversion efficiencies in the range of 0.67–1.67%. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2948–2958

Two new quinoxaline-based polymers, poly[1,5-didecyloxynaphthalene-alt-5,5′-(5,8-dithiophen-2-yl)-2,3-bis(4-octyloxyphenyl)quinoxaline (PNQx-p) and poly[1,5-didecyloxynaphthalene-alt-5,5′-(5,8-dithiophen-2-yl)-2,3-bis(3-octyloxyphenyl)quinoxaline (PNQx-m), were synthesized by Suzuki coupling reaction and characterized. Thermogravimetric analysis revealed that these polymers are thermally stable with degradation temperature up to 320 °C. As evident from the electrochemical and optical studies, the copolymers have comparable optical band gap (∼2 eV) and nearly similar deep highest occupied molecular orbital (HOMO) energy levels of −5.59 (PNQx-p) and −5.61 eV (PNQx-p). The resulting copolymers possessed relatively low HOMO energy levels promising good air stability and high open circuit voltage (Voc) for photovoltaic applications. The optimized photovoltaic device with a structure of ITO/PEDOT:PSS/PNQx-m:PC71BM (1:2, w/w)/LiF/Al shows a power conversion efficiency up to 2.29% with a short circuit current density of 5.61 mA/cm2, an Voc of 0.93 V and a fill factor of 43.73% under an illumination of AM 1.5, 100 mW/cm2. The efficiency of the PNQx-m polymer improved from 2.29 to 2.95% using 1,8-diiodoocane as an additive (0.25%). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

A new polyfluorene derivative (PF-GOH) containing repeated ethylenoxy units linked to glycerol as side chains was synthesized as an electron injection material. The polymer was not very soluble in methanol, but reasonably soluble in mixed solvents such as methanol/ethylene glycol (EG) and isopropyl alcohol (IPA)/EG. Polymer light-emitting diodes (PLEDs) were fabricated with a ITO/PEDOT:PSS/MEH-PPV/PF-GOH/Al configuration. The PLEDs exhibited significantly improved performance in the presence of the PF-GOH layer compared to the device without the electron injection polymer layer. The performance of the PLEDs was largely dependent on the solvent systems employed. Among methanol, methanol/EG (3:1), and IPA/EG (1:1), the best performance was obtained when IPA/EG (1:1) was used. The improved performance was attributed to the more uniform thickness of the electron injection layer of PF-GOH, leading to much less current leakage.

In this work, we have designed and synthesized a new naphtho[1,2-b:5,6-b′]dithiophene-containing enlarged π-conjugated donor–acceptor (D–A) small molecule, NDT(TTz)2, for use in solution-processed organic photovoltaics. NDT(TTz)2, which contains a thiophene-bridged naphtho[1,2-b:5,6-b′]dithiophene as the central fused core and triphenylamine-flanked thiophene thiazolothiazole as a spacer, was synthesized via sequential Suzuki and Stille coupling reactions. The thermal, physiochemical, and electrochemical properties of NDT(TTz)2 have been evaluated by differential scanning calorimetry, thermogravimetry, UV–Vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction, and cyclic voltammetry. As desired for photovoltaic applications, NDT(TTz)2 possesses good solubility, thermal stability, and a well-ordered, π–π stacked, crystallinity. The optical band gap and HOMO level of NDT(TTz)2 were determined to be 2.0 eV and −5.23 eV, respectively. In addition to organic thin film transistor studies, application of NDT(TTz)2 to preliminary photovoltaic devices has also been investigated by fabricating solution-processed bulk heterojunction solar cells together with PC71BM in a typical layered device structure, ITO/PEDOT:PSS/NDT(TTz)2:PC71BM/LiF/Al. Without extensive optimization of the device, NDT(TTz)2 in these devices shows a maximum power conversion efficiency of 1.44% under AM 1.5 illumination at a 100 mW/cm2 intensity.

As an alternative platinum counter electrode in dye-sensitized solar cells (DSSCs), carbon materials based counter electrode were prepared using multi-walled carbon nanotubes (MWNTs)/graphene nano-sheets (GNS) composite by simple doctor blade method. We found that the photovoltaic performance was strongly influenced by the concentration of GNS in composite electrode. The composite electrode with 60% MWNTs and 40% GNS based DSSCs showed the maximum power conversion efficiency of 4.0% while sputter deposited platinum counter electrode based DSSCs showed a power conversion efficiency of 5.0%.

Newly proposed polymer electrolyte membranes (PEMs) composed of an electrospun poly(vinylidene fluoride) (PVDF) fibrous mat embedded in a poly(4-vinylpyridine) (P4VP) matrix were successfully fabricated in order to improve the mechanical and dimensional stabilities and ionic conductivity of membranes in lithium rechargeable batteries. Fourier transform infrared spectroscopic analysis showed that as a result of the use of a high voltage during electrospinning the crystalline structure of PVDF changed partially from α-phase to β-phase. Energy-dispersive X-ray spectroscopy confirmed the existence of crosslinked P4VP in the PVDF fibrous mat. The electrolyte uptakes of PVDF and PVDF/P4VP composite mats were higher than that of PVDF cast film. The tensile properties of PVDF/P4VP composite mat were considerably improved compared to those of the pristine PVDF fibrous mat under both dry and wet (soaked with electrolyte) conditions. In addition, the mechanical and dimensional stabilities of the PVDF/P4VP composite PEM were further enhanced due to crosslinking between the P4VP chains. Furthermore, the PVDF/P4VP composite PEM exhibited an ionic conductivity that was an order of magnitude higher than that of traditional PVDF film. © 2012 Society of Chemical Industry

We synthesised a tetrathiafulvalene (TTF) derivative having an asymmetric structure of a TTF mesogenic core and long alkyl chains which shows a highly ordered columnar liquid crystalline phase at room temperature. A bulk heterojunction photovoltaic cell was fabricated by using the TTF liquid crystal compound (a-6TTF12) as an electron donor and [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) as an electron acceptor. The photoconversion efficiency (PCE) of the cell was very low (0.063%) as prepared, which increased to 0.120% after thermal annealing at 80°C for 20 min. The annealing effect was investigated by means of UV spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) and energy-dispersive X-ray spectroscopy (EDS). The morphological observations of the annealed a-6TTF12: PC60BM composite film indicate that the higher PCE was attributed to the enhanced ordering of TTF molecules by the thermal annealing process to form a highly ordered co...

Two new conjugated polymers, PQSS and PQST, were designed and synthesized; these polymers had alkylselenophene-substituted quinoxaline backbones with selenophene and thiophene, respectively, as electron-donating units. The copolymers showed good solubility and film forming abilities, combined with good thermal stability. The number-average molecular weights ( M n ) of PQSS and PQST, determined using gel permeation chromatography (GPC) with a polystyrene standard, were found to be 20,900 ( M w / M n = 1.71) and 22,100 ( M w / M n = 2.41), respectively. The UV–visible absorption maxima of PQSS and PQST were at 617 and 601 nm in solution, and at 682 and 668 nm in the film state. The PQSS and PQST showed low band gaps of 1.50 and 1.52 eV, respectively. Solution-processed field-effect transistors fabricated from these polymers had p-type organic thin film transistor characteristics. The field-effect mobilities of PQSS and PQST were measured to be 1.4 × 10 −4 and 4.8 × 10 −5 cm 2 V −1 s −1 , respectively. The polymers were combined with a PC 71 BM ([6,6]-phenyl C 71 -butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells, which produced power conversion efficiencies of 0.40–1.07% under AM 1.5G (100 mW/cm 2 ) conditions.

Three solvent systems, chlorobenzene (ink 1), chlorobenzene/o-dichlorobenzene (ink 2) and chlorobenzene/ tetrahydronaphthalene (ink 3), were compared as printable inks for the fabrication of polymer light-emitting diodes (PLEDs) using poly[2-methoxy-5-(2-ethylhexyl-oxyl)-1,4-phenylenevinylene (MEH-PPV) as an emissive material and an inkjet printer (Fujifilm Dimatix DMP-2831). Ink 1 clogged the printer’s nozzle and gave non-uniform film. Inks 2 and 3 were used to fabricate PLEDs with ITO/PEDOT:PSS/MEH-PPV/LiF/Al configurations. The best performance (turn-on voltage, 3.5 V; luminance efficiency, 0.17 cd/A; luminance, 1,800 cd/m) was obtained when ink 3 was used to form the emissive layer (thickness, 49 nm), attributable to the better morphology and suitable thickness of the MEH-PPV layer.

Two new small molecules, 5,5-bis(2-triphenylamino-3-decylthiophen-2-yl)-2,2-bithiazole ( M1 ) and 2,5-bis(2-triphenylamino-3-decylthiophen-2-yl)thiazolo[5,4-d]thiazole ( M2 ) based on an electron-donor triphenylamine unit and electron-acceptor thiophene–thiazolothiazole or thiophene–bithiazole units were synthesized by a palladium(0)-catalyzed Suzuki coupling reaction and examined as donor materials for application in organic solar cells. The small molecules had an absorption band in the range of 300–560 nm, with an optical band gap of 2.22 and 2.25 for M1 and M2 , respectively . As determined by cyclic voltammetry, the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of M1 were −5.27 eV and −3.05 eV, respectively, which were 0.05 eV and 0.02 eV greater than that of M2 . Photovoltaic properties of the small molecules were investigated by constructing bulk-heterojunction organic solar cell (OSC) devices using M1 and M2 as donors and fullerene derivatives, 6,6-phenyl-C61-butyric acid methyl ester (PC 61 BM) and 6,6-phenyl-C71-butyric acid methyl ester (PC 71 BM) as acceptors with the device architecture ITO/PEDOT:PSS/ M1 or M2 :PCBM/LiF/Al. The effect of the small molecule/fullerene weight ratio, active layer thickness, and processing solvent were carefully investigated to improve the performance of the OSCs. Under AM 1.5 G 100 mW/cm 2 illumination, the optimized OSC device with M1 and PC 71 BM at a weight ratio of 1:3 delivered a power conversion efficiency (PCE) of 1.30%, with a short circuit current of 4.63 mA/cm 2 , an open circuit voltage of 0.97 V, and a fill factor of 0.29. In contrast, M2 produced a better performance under identical device conditions. A PCE as high as 2.39% was recorded, with a short circuit current of 6.49 mA/cm 2 , an open circuit voltage of 0.94 V, and a fill factor of 0.39.

In order to investigate the relationships between chemical structures of conjugated polymers and their properties with respect to photovoltaic applications, two new copolymers consisting of an electron-deficient tetrazine unit and either an electron-rich carbazole (PCTz) or fluorene (PFTz) along with thiophene spacers were synthesized. The estimated electrochemical bandgap and HOMO level of PCTz and PFTz were 2.23/−5.32 eV and 2.48/−5.60 eV, respectively. PCTz had a very high absorption coefficient, which was even higher than poly(3-hexyltiophene) in chloroform solution. The bulk heterojunction photovoltaic devices fabricated using PCTz and [6,6]-phenyl-C71-butyric acid methyl ester had a high open-circuit voltage (1.0 V) under AM 1.5 G illumination at 100 mW/cm2 with a power conversion efficiency of 2.13%.

Two novel conjugated polymers consisting of alternating thieno[3,4-b]thiophene and either carbazole (PCTT1) or carbazole with two thiophene spacers (PCTT2) were synthesized. PCTT1 (M n 44,000) showed a bandgap of 2.14 eV but a significantly deep highest occupied molecular orbital level of -5.52 eV. PCTT1-based photovoltaic devices showed promising power conversion efficiency of 2.53% under AM 1.5 G illumination at 100 mW/cm2.

Three new polymers poly(3,4′′′-didodecyl) hexaselenophene) (P6S), poly(5,5′-bis(4,4′-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (HHP6S), and poly(5,5′-bis(3′,4-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (TTP6S) that have the same selenophene-based polymer backbone but different side chain patterns were designed and synthesized. The weight-averaged molecular weights (Mw) of P6S, HHP6S, and TTP6S were found to be 19,100, 24,100, and 19,700 with polydispersity indices of 2.77, 1.48, and 1.41, respectively. The UV–visible absorption maxima of P6S, HHP6S, and TTP6S are at 524, 489, and 513 nm, respectively, in solution and at 569, 517, and 606 nm, respectively, in the film state. The polymers P6S, HHP6S, and TTP6S exhibit low band gaps of 1.74, 1.95, and 1.58 eV, respectively. The field-effect mobilities of P6S, HHP6S, and TTP6S were measured to be 1.3 × 10−4, 3.9 × 10−6, and 3.2 × 10−4 cm2 V−1 s−1, respectively. A photovoltaic device with a TTP6S/[6,6]-phenyl C71-butyric acid methyl ester (1:3, w/w) blend film active layer was found to exhibit an open circuit voltage (VOC) of 0.71 V, a short circuit current (JSC) of 5.72 mA cm−2, a fill factor of 0.41, and a power conversion efficiency (PCE) of 1.67% under AM 1.5 G (100 mW cm−2) illumination. TTP6S has the most planar backbone of the tested polymers, which results in strong π–π interchain interactions and strong aggregation, leading to broad absorption, high mobility, a low band gap, and the highest PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011