From green remediation to polymer hybrid fabrication with improved optical band gaps

The present work proposed a novel approach for transferring high-risk heavy metals tometal complexes via green chemistry remediation. The method of remediation of heavy metals developed in the present work is a great challenge for global environmental sciences and engineering because it is a totally environmentally friendly procedure in which black tea extract solution is used. The FTIR study indicates that black tea contains enough functional groups (OH and NH), polyphenols and conjugated double bonds. The synthesis of copper complex was confirmed by the UV-vis, XRD and FTIR spectroscopic studies. The XRD and FTIR analysis reveals the formation of complexation between Cu metal complexes and Poly (Vinyl Alcohol) (PVA) host matrix. The study of optical parameters indicates that PVA-based hybrids exhibit a small optical band gap, which is close to inorganic-based materials. It was noted that the absorption edge shifted to lower photon energy. When Cu metal complexes were added to PVA polymer, the refractive index was significantly tuned. The band gap shifts from 6.2 eV to 1.4 eV for PVA incorporated with 45 mL of Cu metal complexes. The nature of the electronic transition in hybrid materials was examined based on the Taucs model, while a close inspection of the optical dielectric loss was also performed in order to estimate the optical band gap. The obtained band gaps of the present work reveal that polymer hybrids with sufficient film-forming capability could be useful to overcome the drawbacks associated with conjugated polymers. Based on the XRD results and band gap values, the structure-property relationships were discussed in detail. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Conducting polymers for optoelectronic devices and organic solar cells : a review

In this review paper, we present a comprehensive summary of the different organic solar cell (OSC) families. Pure and doped conjugated polymers are described. The band structure, electronic properties, and charge separation process in conjugated polymers are briefly described. Various techniques for the preparation of conjugated polymers are presented in detail. The applications of conductive polymers for organic light emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic photovoltaics (OPVs) are explained thoroughly. The architecture of organic polymer solar cells including single layer, bilayer planar heterojunction, and bulk heterojunction (BHJ) are described. Moreover, designing conjugated polymers for photovoltaic applications and optimizations of highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy levels are discussed. Principles of bulk heterojunction polymer solar cells are addressed. Finally, strategies for band gap tuning and characteristics of solar cell are presented. In this article, several processing parameters such as the choice of solvent(s) for spin casting film, thermal and solvent annealing, solvent additive, and blend composition that affect the nano-morphology of the photoactive layer are reviewed

Characteristics of low band gap copolymers containing anthracene-benzothiadiazole dicarboxylic imide: synthesis, optical, electrochemical, thermal and structural studies

Two novel low band gap donor–acceptor (D–A) copolymers, poly[9,10-bis(4-(dodecyloxy)phenyl)-2,6-anthracene-alt-5,5-(4′,7′-bis(2-thienyl)-2′,1′,3′-benzothiadiazole-N-5,6-(3,7-dimethyloctyl)dicarboxylic imide)] (PPADTBTDI-DMO) and poly[9,10-bis(4-(dodecyloxy)phenyl)-2,6-anthracene-alt-5,5-(4′,7′-bis(2-thienyl)-2′,1′,3′-benzothiadiazole-5,6-N-octyl-dicarboxylic imide)] (PPADTBTDI-8) were synthesized in the present work by copolymerising the bis-boronate ester of 9,10-phenylsubstituted anthracene flanked by thienyl groups as electron–donor units with benzothiadiazole dicarboxylic imide (BTDI) as electron–acceptor units. Both polymers were synthesized in good yields via Suzuki polymerisation. Two different solubilizing alkyl chains were anchored to the BTDI units in order to investigate the impact upon their solubilities, molecular weights, optical and electrochemical properties, structural properties and thermal stability of the resulting polymers. Both polymers have comparable molecular weights and have a low optical band gap (Eg) of 1.66 eV. The polymers have low-lying highest occupied molecular orbital (HOMO) levels of about −5.5 eV as well as the similar lowest unoccupied molecular orbital (LUMO) energy levels of −3.56 eV. Thermogravimetric analyses (TGA) of PPADTBTDI-DMO and PPADTBTDI-8 did not prove instability with decomposition temperatures at 354 and 313 °C, respectively. Powder X-ray diffraction (XRD) studies have shown that both polymers have an amorphous nature in the solid state, which could be used as electrolytes in optoelectronic devices

Influence of fluorine substitution on the optical, thermal, electrochemical and structural properties of carbazole-benzothiadiazole dicarboxylic imide alternate copolymers

In this work four novel donor-acceptor copolymers, PCDTBTDI-DMO, PCDTBTDI-8, P2F-CDTBTDI-DMO and P2F-CDTBTDI-8, were designed and synthesised via Suzuki polymerisation. The first two copolymers consist of 2,7-carbazole flanked by thienyl moieties as the electron donor unit and benzothiadiazole dicarboxylic imide (BTDI) as electron acceptor units. In the structures of P2F-CDTBTDI-DMO and P2F-CDTBTDI-8 copolymers, two fluorine atoms were incorporated at 3,6-positions of 2,7-carbazole to investigate the impact of fluorine upon the optoelectronic, structural and thermal properties of the resulting polymers. P2F-CDTBTDI-8 possesses the highest number average molecular weight (Mn = 24,200 g mol−1) among all the polymers synthesised. PCDTBTDI-DMO and PCDTBTDI-8 show identical optical band gaps of 1.76 eV. However, the optical band gaps of fluorinated copolymers are slightly higher than non-fluorinated counterparts. All polymers have deep-lying highest occupied molecular orbital (HOMO) levels. Changing the alkyl chain substituents on BTDI moieties from linear n-octyl to branched 3,7-dimethyloctyl groups as well as substituting the two hydrogen atoms at 3,6-positions of carbazole unit by fluorine atoms has negligible impact on the HOMO levels of the polymers. Similarly, the lowest unoccupied molecular orbital (LUMO) energy levels are almost comparable for all polymers. Thermogravimetric analysis (TGA) has shown that all polymers have good thermal stability and also confirmed that the fluorinated copolymers have higher thermal stability relative to those non-fluorinated analogues. Powder X-ray diffraction (XRD) studies proved that all polymers have an amorphous nature in the solid state

Fabrication of alternating copolymers based on cyclopentadithiophene-benzothiadiazole dicarboxylic imide with reduced optical band gap: synthesis, optical, electrochemical, thermal, and structural properties

A series of alternating copolymers containing cyclopentadithiophene (CPDT) flanked by thienyl moieties as electron-donor units and benzothiadiazole dicarboxylic imide (BTDI) as electron-acceptor units were designed and synthesized for solar cell applications. Different solubilizing side chains, including 2-ethylhexyl chains and n-octyl chains were attached to CPDT units, whereas 3,7-dimethyloctyl chains and n-octyl chains were anchored to the BTDI moieties. The impact of these substituents on the solubilities, molecular weights, optical and electrochemical properties, and thermal and structural properties of the resulting polymers was investigated. PCPDTDTBTDI-EH, DMO was synthesized via Suzuki polymerization, whereas PCPDTDTBTDI-8, DMO, and PCPDTDTBTDI-EH, 8 were prepared through direct arylation polymerization. PCPDTDTBTDI-8, DMO has the highest number average molecular weight (Mn = 17,400 g mol−1) among all polymers prepared. The PCPDTDTBTDI-8, DMO and PCPDTDTBTDI-8, 8 which have n-octyl substituents on their CPDT units have comparable optical band gaps (Eg ~ 1.3 eV), which are around 0.1 eV lower than PCPDTDTBTDI-EH, DMO analogues that have 2-ethylhexyl substituents on their CPDT units. The polymers have their HOMO levels between −5.10 and −5.22 eV with PCPDTDTBTDI-EH, DMO having the deepest highest occupied molecular orbital (HOMO) energy level. The lowest unoccupied molecular orbital (LUMO) levels of the polymers are between −3.4 and −3.5 eV. All polymers exhibit good thermal stability with decomposition temperatures surpassing 350 °C. Powder X-ray diffraction (XRD) studies have shown that all polymers have the amorphous nature in solid state

Metal framework as a novel approach for the fabrication of electric double layer capacitor device with high energy density using plasticized Poly(vinyl alcohol): Ammonium Thiocyanate based Polymer Electrolyte

High performance electric double-layer capacitors (EDLCs) based on poly (vinyl alcohol) (PVA): ammonium thiocyanate (NH4SCN):Cu(II)-complex plasticized with glycerol (GLY) have been fabricated. The maximum DC ionic conductivity (σDC) of 2.25 × 10-3 S cm-1 is achieved at ambient temperature. The X-ray diffraction (XRD) patterns confirmed that the addition of both Cu(II)–complex and GLY enhanced the amorphous region within the samples. Through the Fourier transform infrared (FTIR) the interactions between the host polymer and other components of the prepared electrolyte are observed. The FESEM images reveal that the surface morphology of the samples showed a uniform smooth surface at high GLY concentration. This is in good agreement with the XRD and FTIR results. Transference numbers of ion (tion) and electron (tel) for the highest conducting composite polymer electrolyte (CPE) are recognized to be 0.971 and 0.029, respectively. The linear sweep voltammetry (LSV) revealed that the electrochemical stability window for the CPE is 2.15 V. These high values of tion and potential stability established the suitability of the synthesized systems for EDLC application. Cyclic voltammetry (CV) offered nearly rectangular shape with the lack of Faradaic peak. The specific capacitance and energy density of the EDLC are nearly constant within 1000 cycles at a current density of 0.5 mA/cm2 with average of 155.322 F/g and 17.473 Wh/Kg, respectively. The energy density of the EDLC in the current work is in the range of battery specific energy. The EDLC performance was found to be stable over 1000 cycles. The low value of equivalent series resistance reveals that the EDLC has good electrolyte-electrode contact. The EDLC exhibited the initial high power density of 4.960 × 103 W/K

Electrochemical impedance spectroscopy as a novel approach to investigate the influence of metal complexes on electrical properties of poly (vinyl alcohol)(PVA) composites

In the current study, black tea leaves extract solution (TES) as a new green technique is used to fabricate metal-polyphenols complexes (X-polyphenols complex; X= Cu+2, Ce+3, and Cd+2). The metal-complexes are integrated with poly (vinyl alcohol) (PVA) to prepare PVA composite films. The electrical properties of pure PVA and composites are characterized using the electrochemical impedance spectroscopy (EIS) method. The EIS data are fitted to the electrical equivalent circuit to evaluate the impedance parameters of pure PVA and composite films. The trend of DC conductivity is further verified by dielectric analysis. The electrical parameters are considerably improved upon incorporating with the metal-complexes. The effects of the metal-complexes on the modification of PVA are compared together. The PVA composite incorporated with the Cu+2-complex shows the highest DC conductivity and dielectric constant, which is important for application in electrochemical energy storage devices such as batteries and supercapacitors, in comparison with the Ce+3- and Cd+2- complexes

Effect of ohmic-drop on electrochemical performance of EDLC fabricated from PVA:dextran:NH4I based polymer blend electrolytes

Proton conducting solid polymer blend electrolytes based on poly(vinyl alcohol)(PVA):dextran that were doped with different quantities of ammonium iodide (NH4I) were prepared. The X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) study were carried out to examine the compatibility of NH4I withPVA:dextran polymers. FTIR spectroscopy assessment was used to establish the presence of a complex formation between the PVA:dextran and added salt through the modification and reduction in the intensity of FTIR bands relevant to the functional groups. The field emission scanning electron microscopy (FESEM) examination was used to assess the channels for proton transport. Electrical impedance spectroscopy (EIS) was used to analyse the samples conductivity behaviour. The sample with 20 wt.% of added salt has shown a high DC conductivity which can be employed in electrochemical devices such as EDLC. It is also demonstrated by the transference number (TNM) and linear sweep voltammetry (LSV) that it is appropriate to use the largest conducting sample for electrochemical device. There was electrochemical stability of the electrolyte sample with voltage sweeping linearly to 1.3 V. It is shown by the outcome of cyclic voltammetry (CV) plot that charge storage at the site of electrode-electrolyte is non-Faradiac. A high drop voltage (Vd=IR) is implied by the usual galvanostatic charge-discharge. The equivalent series resistance (Res) increases as a result of the increase in Vd all the way through the charge-discharge cycle. Specific capacitance (Csp) is nearly constant from the foremost cycle to the 100th cycle, with average of 4.2 F/g

Compatible solid polymer electrolyte based on methyl cellulose for energy storage application: structural, electrical, and electrochemical properties

Compatible green polymer electrolytes based on methyl cellulose (MC) were prepared for energy storage electrochemical double-layer capacitor (EDLC) application. X-ray diffraction (XRD) was conducted for structural investigation. The reduction in the intensity of crystalline peaks of MC upon the addition of sodium iodide (NaI) salt discloses the growth of the amorphous area in solid polymer electrolytes (SPEs). Impedance plots show that the uppermost conducting electrolyte had a smaller bulk resistance. The highest attained direct current DC conductivity was 3.01 × 10−3 S/cm for the sample integrated with 50 wt.% of NaI. The dielectric analysis suggests that samples in this study showed non-Debye behavior. The electron transference number was found to be lower than the ion transference number, thus it can be concluded that ions are the primary charge carriers in the MC–NaI system. The addition of a relatively high concentration of salt into the MC matrix changed the ion transfer number from 0.75 to 0.93. From linear sweep voltammetry (LSV), the green polymer electrolyte in this work was actually stable up to 1.7 V. The consequence of the cyclic voltammetry (CV) plot suggests that the nature of charge storage at the electrode–electrolyte interfaces is a non-Faradaic process and specific capacitance is subjective by scan rates. The relatively high capacitance of 94.7 F/g at a sweep rate of 10 mV/s was achieved for EDLC assembly containing a MC–NaI system

Structural and electrochemical studies of proton conducting biopolymer blend electrolytes based on MC:Dextran for EDLC device application with high energy density

This study shows preparation and characterization of solid biopolymer electrolyte based on glycerolized methylcellulose (MC): dextran-doped with ammonium thiocyanate (NH4SCN). The nature of electrolyte composition in terms of interaction is characterized using Fourier transform infrared (FTIR) technique. Lowering and shifting in the intensity of the bands are observed with increasing the quantity of glycerol as a plasticizer, confirming complexation between electrolyte components. Ion transport parameters are determined using both of the methods of EIS and FTIR where the parameters are found to be increased with glycerol concentration. The transport number measurement indicates that ions are the primary charge carrier in the conduction mechanism where tion is found to be 0.961. The maximum DC ionic conductivity value is achieved that found to be 1.63 � 10�3 S cm�1. The ESR values are ranged from 300 to 580 O throughout 450 cycles. The technique of linear sweep voltammetry (LSV) shows the electrochemical stability window of 2 V for the conducting samples. The response of cyclic voltammetry (CV) shows an almost rectangular shape without Faradaic peaks. A galvanostatic charge–discharge investigation has shown the initial specific capacitance, energy density, and power density are 133 F g�1, 18.3 Wh Kg�1, and 680 W Kg�1, respectively