Design and synthesis of triazoloquinoxaline polymers with positioning alkyl or alkoxyl chains for organic photovoltaics cells

Abstract

Four benzodithiophene-triazoloquinoxaline alternating polymers, PBDTT-BTzQx-EH-C1, PBDT-BTzQx-EH-C1, PBDT-BTzQx-EH-C12 and PBDT-BTzQx-C12, have been designed and synthesized to investigate the correlation of alkyl side chains with the opto-electronic properties of the resulting polymers. The introduction of side chains onto the thiophene spacer or quinoxaline unit lowers the highest occupied molecular orbital energy level of the polymers, while excessive chains prevent the polymer backbone from p-p stacking and result in a decreased short circuit current and fill factor in a photovoltaic application. The bulk heterojunction cells fabricated by blending PBDTT-BTzQx-EH-C1 with [6,6]phenyl-C61-butyric acid methyl ester exhibit a best power conversion efficiency (PCE) of 1.40%, with a short-circuit current density of 4.12 mA cm À2 , an open-circuit voltage of 0.62 V and a fill factor of 55%.The device was further optimized to 2.24% PCE by using PFN (5 nm)/Ca (5 nm) as a co-interfacial layer.

Effect of carbon hybridization in 9H-fluorene unit on the photovoltaic properties of different fluorene-based conjugated polymers

“…The characteristics are summarized in Table 1. Similar to the TzQx-based polymers, these substituted 9H-fluorene-based polymers exhibit two major absorption bands, 23,24,28,29 in which simple benzotriazole-based polymers only show one broad absorption band. 30 –32 The weak absorption at shorter wavelength is attributed to the π–π* transitions of the conjugated main chain and the strong absorption at the longer wavelength is owed to the intermolecular charge transfer interaction between the substituted 9H-fluorene donating unit and TzQx accepting unit.…”

“…The intermediate 2-dodecyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole-5,6-diamine ( 1 ) and 1,2-bis(3,4-bis(dodecyloxy)phenyl)ethane-1,2-dione ( 2 ) were synthesized according to our reported procedure. 23 The ring-closure reaction between the compounds 1 and 2 produced the compound 6,7-bis(3,4-bis(dodecyloxy)phenyl)-2-dodecyl-4,9-di(thiophen-2-yl)-2H-[1,2,3]triazolo[4,5-g]quinoxaline ( 3 ). The bromination of 3 readily afforded monomer 4 , that is, 6,7-bis(3,4-bis(dodecyloxy)phenyl)-4,9-bis(5-bromothiophen-2-yl)-2-dodecyl-2H-[1,2,3]triazolo[4,5-g]quinoxaline.…”

“…The synthesis of 2-dodecyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole-5,6-diamine ( 1 ), 1,2-bis(3,4-bis(dodecyloxy)phenyl)ethane-1,2-dione ( 2 ), 2,2′-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) ( 5 ), 2,2′-(9-(tridecan-7-ylidene)-9H-fluorene-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) ( 6 ), 2,2′-(9-((5-dodecylthiophen-2-yl)methylene)-9H-fluorene-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) ( 7 ), andN-(4-methoxyphenyl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-fluoren-9-imine ( 8 ) has been reported in previous reported procedure. 20,23,24…”

Thiadiazole quinoxaline-based copolymers with ∼1.0 eV bandgap for ternary polymer solar cells

“…we have reported some quinoxaline-based copolymers with different bandgaps from 1.13 eV to 1.66 eV [41][42][43]. Compared with these polymers with the same D unit, thiadiazole quinoxaline-based polymers exhibit lower bandgaps than triazole …”

Synthesis and Photovoltaic Characterization of Dithieno[3,2‐b:2′,3′‐d]thiophene‐Derived Narrow‐Bandgap Polymers

“…An appropriate choice of monomers in the backbone of a semiconducting polymer can push their optical absorbance toward the near‐infrared region. One strategy is to incorporate electron‐rich donor (D) units and electron‐deficient acceptor (A) segments in the polymer backbone to construct D–A alternating narrow‐bangap polymers . Through controlling the intramolecular charge transfer (ICT) from D to A moieties, the energy gap of the conjugated polymers decreases thus shifting the absorption band to lower energy.…”