Synthesis of D‐π‐A‐π type benzodithiophene‐quinoxaline copolymers by direct arylation and their application in organic solar cells

Abstract

Conjugated copolymers based on benzodithiophene (BDT) derivatives and thiophene‐quinoxaline‐thiophene (TQT) segments represent an efficient class of light harvesting materials for organic photovoltaic (OPV) applications. Commonly, BDT‐TQT copolymers are synthesized by Stille cross‐coupling polymerization. In this study, alkoxy and thienyl functionalized alternating BDT‐alt‐TQT copolymers are synthesized by direct arylation polymerization (DArP), using Ozawa conditions. An extensive optimization of the reaction conditions such as the catalytic system, solvent, temperature, base, and the concentration of the catalyst is accomplished. The optical and electrochemical properties of the copolymers obtained by DArP are compared to the reference polymers synthesized by Stille cross‐coupling polymerization. Finally, the optimized BDT‐alt‐TQT copolymers are incorporated into organic solar cells as electron donors. The solar cells of the DArP copolymers exhibit power conversion efficiencies up to 80% (rel.) of their Stille cross coupling analogues. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1457–1467

Thermal Stabilization of the Bulk‐Heterojunction Morphology in Polymer:Fullerene Solar Cells Using a Bisazide Cross‐Linker

“…To evidence the generality of this cross‐linking concept, we investigated the effect of TBA‐X and its stabilization abilities on other light‐harvesting bulk‐heterojunctions. More specifically, we have chosen polymer:PC 61 BM bulk‐heterojunctions comprising either of the polymers poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7), its advanced derivative poly[[4,8‐bis[5‐(2‐ethylhexyl)thiophen‐2‐yl]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7‐Th), or the benzodithiophene‐quinoxaline polymer poly(4,8‐bis(5‐(2‐ethylhexyl)thiophene‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐ co ‐5,8‐bis(thiophene‐2‐yl)‐6,7‐difluoro‐2,3‐bis(3‐(octyloxy)‐phenyl)quinoxaline) (PBDTT‐QFF) . PTB7:PC 61 BM and PTB7‐Th:PC 61 BM were deposited from o ‐xylene: p ‐anisaldehyde solution, whereas PBDTT‐QFF:PC 61 BM was applied from o ‐dichlorobenzene:1,8‐diiodooctane solution.…”

“…[44] or the benzodithiophene-quinoxaline polymer poly(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b 0 ] dithiophene-co-5,8-bis(thiophene-2-yl)-6,7-difluoro-2,3-bis(3-(octyloxy)-phenyl)quinoxaline) (PBDTT-QFF). [42,45,46] PTB7: PC 61 BM and PTB7-Th:PC 61 BM were deposited from o-xylene: p-anisaldehyde solution, [47] whereas PBDTT-QFF:PC 61 BM was applied from o-dichlorobenzene:1,8-diiodooctane solution. For reasons of compatibility to industry-relevant processes, we have deliberately restricted our investigations to PC 61 BM which incurs the lowest synthetic costs and provides the best large-quantity availability, even though the device performances may be somewhat lower than the performances of the hero solar cells comprising PC 71 BM that are reported in the literature.…”

New conjugated polymer nanoparticles with high photoluminescence quantum yields for far-red and near infrared fluorescence bioimaging

“…The syntheses of 5,8-dibromo-2,3-bis(3-(octyloxy)phenyl)quinoxaline,5,8-dibromo-6-fluoro-2,3-bis(3-(octyloxy)phenyl)quinoxaline, 5,8-dibromo-6,7-difluoro-2,3-bis(3-(octyloxy)phenyl)quinoxaline and bis(trimethylstannyl)thiophene were performed according to already published procedures. [41][42][43] (3,4-Difluorothiophene-2,5-diyl)bis(trimethylstannane) 44 was purchased from Derthon Optoelectronic Materials Science Technology Co., Ltd and poly(ethylene glycol)methyl ether-poly(lactide-co-glycolide) (mPLGA-b-PEG) [average molecular weight per number of PLGA is % M nPLGA = 7000 g mol À1 , and that of PEG is % M nPEG = 5000 g mol À1 ] was purchased from Sigma Aldrich.…”

Shining Light on Organic Solar Cells

“…These days, concepts are being developed to synthesize light-absorbing polymers using eco-friendly synthesis, [55] e.g., by direct arylation polymerization to replace Stille coupling and therefore to omit toxic catalysts. [56] Although direct arylation provides several pitfalls for the synthetic procedure, and although, as of today, not all polymers can be synthesized using nontoxic chemistry, the results that have been reported so far are very encouraging for a future sustainable polymer synthesis. Attempting to use more natural educts for the synthesis of organic semiconductors in the future would add further sustainability to the technology.…”