5,10-Dihydroindolo[3,2-b]indole-Based Copolymers with Alternating Donor and Acceptor Moieties for Organic Photovoltaics

Abstract

A series of new donor−acceptor π-conjugated copolymers incorporating 5,10-dihydroindolo [3,2-b]indole (DINI) as an electron donating unit have been designed, synthesized, and explored in bulk heterojunction solar cells with diketopyrrolopyrrole and thienopyrroledione as the electron accepting units. A significant effect of the size and shape of the pendant alkyl substituents attached to the DINI unit on the optical and electronic properties of the copolymers is described. Our study reveals a good correlation between the theoretical calculations performed on the selected materials and the experimental HOMO, LUMO, absorption spectra, and band gap energies of the corresponding copolymers. The band gaps of the conjugated copolymers can be tailored over 0.4 eV by the electron-withdrawing nature of the different acceptor units to provide better overlap with the solar spectrum, and the energy levels can be tuned ∼0.2 eV depending on the alkyl substituents employed. For the polymers in this study, a nonoptimized power conversion efficiency as high as 3% was observed.

Effect of Acceptor Strength on Optical and Electronic Properties in Conjugated Polymers for Solar Applications

“…[20][21][22][23][24][25][26][27] One group of polymers which has been developed using this approach, and has been reported to have PCEs larger than 8% in photovoltaic devices, is the poly(thienothiophenebenzodithiophene) (PTB) polymer series. These polymers contain repeating units of alternating thieno[3,4-b]thiophene (TT) and benzodithiophene (BDT).…”

Applications of Bartoli indole synthesis

“…Of those, over 200 are currently marked as drugs or undergoing clinical trials. 12 Furthermore, the indole nucleus is not only important in biological systems and in pharmaceutical research, but it is also a common moiety in material science, [13][14][15] so it is referred to as ''privileged structure''. Therefore, the a Dipartimento Chimica Industriale 'Toso Montanari', Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy.…”

Synthesis and Characterization of New Dihydroindolo[3,2-b]indole and 5,6-Bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole-Based Polymer for Bulk Heterojunction Polymer Solar Cells

“…The synthesis of monomers described in experimental section was followed from previously published literature. [16][17][18][19] Sonogashira Pd-catalyzed crosscoupling of o-iodonitrobenzene with acetylene yielded 2,2'-dinitrotolane, after oxidation of 2,2'-dinitrotolane to dione, followed by ring closure, N-alkylation with NaH and bromination with NBS resulted DINI monomer. After borylation of DINI, the resulted monomer was copolymerized with OBTC8 by using Suzuki polycondensation reaction conditions to obtain PDINI-OBTC8 with high molecular weight (30000 g/mol) and good solubility.…”