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The photovoltaic performance of blends of a series of 4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacenes)-based (BODIPY) conjugated polymers donors with fullerene electron acceptors is investigated. Despite the high Voc values observed, solar cell device yields relatively low power conversion efficiencies. Our study takes into account the materials’ structure-property relationship, light harvesting capabilities, charge transport, collection properties and morphological characteristics to elucidate factors affecting the photovoltaic performance in this class of polymers. We show that elimination of low molecular weight species and suitable electrodes for hole collection can be used to overcome some of the observed limitations on photovoltaic performance. [ABSTRACT FROM AUTHOR]

Abstract: A series of variable alkyl chain length substituted donor–acceptor (D–A) conjugated polymers with thiophene ring as the donor and benzotriazole moiety as the acceptor has been investigated in bulk heterojunction solar cells. The optical and electrochemical properties showed that the absorption onsets and the energy levels of the copolymers were not affected by alkyl substitution revealing 1.9eV of optical band gap. The morphologies of the blend film can be fine-tuned by increasing the chain length attached to the benzotriazole unit. Photovoltaic devices were fabricated using (6,6)-phenyl-C61-butyric acid methyl ester (PC60BM) and (6,6)-phenyl-C71-butyric acid methyl ester (PC70BM) as the acceptors. The maximum performance was achieved with a V oc of 0.75V, J sc of 3.70mA/cm2, FF of 45% and a PCE of 1.23% for the PTBT-DA10:PC70BM device using 1:4 w/w ratio in chlorobenzene (CB). [Copyright &y& Elsevier]

Abstract: 4,7-Bis(2,3-dihydrothieno [3,4-b] [1,4] dioxin-5-yl)-2-dodecyl-2H-benzo [1,2,3] triazole (BEBT) was polymerized both electrochemically (ePBEBT) and chemically (cPBEBT). Since chemical polymerization enabled a soluble polymer in common organic solvents, a single layer electrochromic device of ePBEBT was constructed. The polymer cPBEBT was also used in bulk heterojunction (BHJ) solar cells as the active layer in combination with a soluble fullerene derivative, 1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C61 PCBM. [Copyright &y& Elsevier]

Abstract: Electrochemical copolymerization was utilized to combine several properties into a single material in order to obtain a highly stable polymer with a low band gap to meet the requirements for color variation. In that sense, two new donor acceptor type electrochromic copolymers of 2,3-bis(4-tert-butylphenyl)-5,8-di(1H-pyrrol-2-yl) quinoxaline (TBPPQ) with bis(3,4-ethylenedioxythiophene) (BiEDOT) and with 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-dodecyl-2H-benzo [1,2,3] triazole (BEBT) were synthesized by electrochemical polymerization. Polymers revealed multicolor electrochromic properties with distinct accessible states and low operation potentials. Electrochromic and kinetic properties of polymers were investigated using cyclic voltammetry (CV) and in situ UV–vis–NIR spectroscopy. [Copyright &y& Elsevier]

Abstract: We report on the photophysical properties and photovoltaic performance of a polythiophene derivative, poly-2,3-bis(4-tert-butylphenyl)-5,8-bis(4-hexylthiophen-2-yl)quinoxaline (PHTQ) as an electron donor in bulk heterojunction solar cells blended with the acceptor 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM). Devices were composed of PHTQ and varying amounts of PCBM (1:1, 1:2, 1:3, 1:4 w-w ratio). The components were spin cast from ortho-dichlorobenzene (ODCB) and characterized by measuring current–voltage characteristics under simulated AM 1.5 conditions. Efficiencies up to 0.3% have been reached. Incident photon to current efficiency (IPCE) is reported and the nanoscale morphology was investigated with atomic force microscopy (AFM). Photoinduced absorption spectroscopy confirms the photoinduced charge transfer in such donor acceptor blends. [Copyright &y& Elsevier]

Abstract: 2-Dodecyl benzotriazole (BTz) and benzothiadiazole (BTd) containing alternating copolymers poly(4-(2-dodecyl-2H-benzo[d][1,2,3]triazol-4-yl)benzo[c][1,2,5]thiadiazole (P1), poly(4-(5-(2-dodecyl-7-(thiophen-2yl)-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)benzo[c] [1,2,5] thiadiazole (P2) and poly(4-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d] [1,2,3]triazol-4-yl) -3-hexylthiophen-2-yl) benzo[c][1,2,5] thiadiazole (P3) were synthesized via Suzuki polycondensation reactions. The solubility of the polymers enabled spray coating to carry out the electrochemical and optical studies. Electronic and optical properties of resulting polymers showed that P2 is a great candidate to be used as processable blue electrochromic polymer which can switch to transparent upon oxidation. P3 was also investigated in terms of its electrochromic performance which has two different colored and a transparent states, whereas P1 does not exhibit any spectral change upon applied potentials. HOMO and LUMO values, band gaps and kinetic behavior of polymers upon externally applied potential are reported in detail. [Copyright &y& Elsevier]

Abstract: Two low band gap conjugated polymers, poly[4,9-bis(4-hexylthien-2-yl)-6,7-di(thien-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline] (PHTTQ) and poly[5,10-bis(4-hexylthien-2-yl)-2,3,7,8-tetra(thien-2-yl)pyrazino[2,3-g]quinoxaline] (PHTPQ), consisting of alternating electron-rich 3-hexylthiophene and electron-deficient 6,7-di(thien-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TTQ) and 2,3,7,8-tetra(thien-2-yl)-2,3-dihydropyrazino[2,3-g]quinoxaline (TPQ) units were synthesized electrochemically. The structures of the π-conjugated monomers were tailored using thiophene as the pendant group on the acceptor units (TTQ and TPQ). The electrochemical and optical properties of the polymers were investigated by cyclic voltammetry and UV–vis–NIR spectroscopy. The absorption spectra of PHTPQ, revealing a 1.0eV band gap, exhibited three maxima at 352nm, 535nm, and 750nm. Consequently, its absorption spectra cover the region between 400 and 800nm, which make the polymer almost black in appearance. PHTTQ shows a λ max value of 820nm and a band gap of 0.8eV which is very low among other [1,2,5]thiadiazolo[3,4-g]quinoxaline-containing donor–acceptor type polymers. [Copyright &y& Elsevier]

Abstract: Two new quinoxaline and ethylenedioxythiophene (EDOT) based polymers; poly(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(phenyll)-3-ferrocenylquinoxaline) (P1) and poly(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(naphthalen-2-yl) quinoxaline) (P2) were synthesized and characterized in terms of their electrochemical and spectroelectrochemical properties. The polymers were both p and n-type dopable. The polymers can be switched between green and transparent states during p-doping/dedoping. They were compared with their previously reported analogues in order to investigate ferrocene pendant group effect on electrochromic characteristics. [ABSTRACT FROM AUTHOR]

Abstract: 2-Dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating copolymers poly((9,9-dioctylfluorene)-2,7-diyl-(2-dodecyl-benzo[1,2,3]triazole)) (P1), poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl-benzo[1,2,3]triazole)) (P2), poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(3-hexylthien-5-yl) 2-dodecyl-benzo[1,2,3]triazole)) (P3) were synthesized via Suzuki polycondensation. Electronic and optical properties of resulting polymers showed that all polymers are both p and n dopable and have multicolored electrochromic states. HOMO and LUMO values, band gaps and spectral response of polymers upon externally applied potential and trifluoro acetic acid (TFA) addition were given in detail. [ABSTRACT FROM AUTHOR]

Abstract: Donor–acceptor–donor (DAD) type benzimidazole (BIm) and 3,4 ethylenedioxythiophene (EDOT) bearing monomers were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance and comparison of results with other well known π-accepting benzazole bearing DAD type polymers were reported in detail. [ABSTRACT FROM AUTHOR]

Abstract: A benzothiadiazole bearing donor–acceptor–donor (D–A–D) type monomer (M3) was synthesized using the combination of 3, 4-ethylenedioxythiophene (EDOT) and thiophene donor units to understand the effect of donor strength on the optoelectronic and electrochemical properties. The resulting monomer was polymerized electrochemically (P3) and compared with its symmetrical thiophene (P1) and EDOT (P2) bearing homologues whether there exists a combination of the electrochemical and optical characteristics. Also, copolymer studies were performed with symmetrical thiophene (M1) and EDOT (M2) containing monomers in order to compare the results with P3. Cyclic voltammetry (CV) and spectroelectrochemistry results revealed that P3 is a low band gap polymer (1.18eV) having both p-and n-type property which is superior to the copolymers synthesized using M1 and M2. [ABSTRACT FROM AUTHOR]

Abstract: Ferrocene substituted donor–acceptor–donor type polymer; poly(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(naphthalen-2-yl)-3-ferrocenyl-4a,8a-dihydroquinoxaline) (PDEFNQ) was synthesized and its electrochromic properties were investigated. Cyclic voltammetry and spectroelectrochemistry studies for PDEFNQ showed that it is a multichromic green to transmissive polymer with high tendency to be both p and n doped. PDEFNQ is foreseen as a promising candidate for various applications. [Copyright &y& Elsevier]

Abstract: A new star-shaped D–π–A molecule, tris{4-[5′′-(1,1-dicyanobut-1-en-2-yl)-2,2′-bithiophen-5-yl]phenyl}amine N(Ph-2T-DCN-Et)3 , with high efficiency potential for photovoltaic applications was synthesized. As compared to its analogue S(TPA-bT-DCN), it showed stronger absorption in the region of 350–450nm and a lower lying highest occupied molecular energy level (HOMO). Solution-processed organic solar cells (OSCs) based on a blend of N(Ph-2T-DCN-Et)3 and PC70BM resulted in a high PCE of 3.1% without any post-treatment. The PCE of N(Ph-2T-DCN-Et)3 based solar cells was further improved to 3.6% under simulated AM 1.5 by addition of a new additive 4-bromoanisole (BrAni). [Copyright &y& Elsevier]

Abstract: Two electroactive monomers 1-benzyl-4,7-di(thiophen-2-yl))-2H-benzo[d][1,2,3]triazole (BBTA) and 2-benzyl-4,7-di(thiophen-2-yl))-2H-benzo[d][1,2,3]triazole (BBTS) were synthesized with satisfactory yields. The effect of substitution site on electrochemical and optical properties was investigated with cyclic voltammetry and spectroelectrochemical studies. Results showed that position of pendant group alters the electronic structure of the resulting polymer causing different optical and electrochemical behaviors. Symmetrically positioned benzyl unit on benzotriazole moiety resulted in a neutral state red polymer, PBBTS, having multi-colored property in its different oxidized and reduced states. Its analogue PBBTA exhibited maximum absorption at 390nm in its neutral state and also revealed multicolored electrochromic property upon stepwise oxidation. Very different optical band gap values were calculated: 1.55eV and 2.25eV for PBBTS and PBBTA, respectively. [Copyright &y& Elsevier]

Abstract: New classes of EDOT coupled-benzotriazole bearing π-conjugated monomers containing benzyl units on electron-withdrawing benzotriazole moiety were synthesized. The effect of structural differences on electrochemical and optoelectronic properties of the resulting polymers (PBBTES and PBBTEA) was investigated. The results showed that the insertion of benzyl substituent to benzotriazole from different positions changes the electronic structure of polymer which results in completely different electrochemical and optical properties. PBBTES has a very low oxidation potential (0.13V) compared to the oxidation potential of PBBTEA (0.98V). Spectroelectrochemical analyses revealed that PBBTES is blue in its neutral state with a π–π* transition at 625nm whereas PBBTEA is orange in its neutral state with a π–π* transition at 477nm. The band gap (E g) values for PBBTES and PBBTEA were calculated as 1.48eV and 1.57eV, respectively. PBBTEA can be switched between blue neutral state and light blue oxidized state while PBBTEA reveals orange color at the neutral state and gray color at oxidized state. [Copyright &y& Elsevier]

Abstract: A new neutral state green polymer, poly (2,3-bis(4-tert-butylphenyl)-5,8-di(1H-pyrrol-2-yl) quinoxaline) (PTBPPQ) was synthesized and its potential use as an electrochromic material was investigated. Spectroelectrochemistry studies showed that polymer reveals two distinct absorption bands as expected for a donor–acceptor type polymer, at 408 and 745nm. In addition, polymer has excellent switching properties with satisfactory optical contrasts and very short switching times. Outstanding optical contrast in the NIR region and stability make this polymer a great candidate for many applications. It should be noted that PTBPPQ is one of the few examples of neutral state green polymeric materials with superior switching properties. Hence, PTBPPQ can be used as a green polymeric material for display technologies. [Copyright &y& Elsevier]