solar cells. [2][3][4][5][6][7][8][9] Typically, polymeric or oligomeric materials comprising covalently linked electron-rich donor (D) and electron-deficient acceptor (A) units are developed. In most examples D and A are connected by flexible insulating linkers of various lengths corresponding to a molecular bulk heterojunction model, whereas only few have rigid π-conjugated linkers or are directly connected. [1] Among the ambipolar D-A polymers, structurally challenging "double cable" polymers with high synthetic complexity [2][3][4][5] very recently showed significantly improved power conversion efficiencies (PCE) to over 8.4% in SMOSCs. In these materials, a lamellar phase-separation of D and A units is typically achieved at higher temperatures (up to 230 °C) resulting in solar cells with high thermal and light stability. [1c,3-5] Currently, these results have been outperformed by random D-A block copolymers [6][7][8] reaching a PCE of 8.6% [7] and even very promising 11.3% [8] catching the 10% technological barrier for industrial applications. [1c,10] It is well accepted that structurally defined semiconducting molecular materials have particular advantages such as monodispersity and reproducibility over polydisperse polymers, which contain chain length distributions and defects to a certain extent. [11] Various oligomeric D-A dyads and triads have been prepared and optimized for SMOSCs over time, [1] and general structural concepts include: 1) D and A are directly connected in an "in-chain" approach leading to fully π-conjugated alternating D-A systems. The best result in this category was achieved with oligo(fluorene-alt-bithiophene)perylene diimide dyads, which after post-treatment with solvent vapor annealing (SVA) gave device performances of up to 1.75% PCE; [12] 2) D and A are linearly linked via flexible linkers in the so-called "side-chain" approach in an 1:1 or 1:2 ratio, whereby an oligothiophene-PC 71 BM fullerene dyad recently described by Min et al. reached a PCE of 3.22% in SMOSCs; [13] 3) Similar to the subunits in "double cable" polymers, oligomeric donor backbones were substituted at the central unit with pending PC 61 BM or PC 71 BM fullerenes in a "T-shaped" fashion, but typically reached efficiencies of only below 2%. [1] An improved performance of up to 2.5% PCE was obtained by the attachment of non-fullerenic perylene diimide side chains to a conjugated cooligomer backbone comprising diketopyrrolopyrrole and benzodithiophene units. [14] We recently could further improve the performance of SMOSCs in this category by developing ambipolar "T-shaped" D-A dyads 1-3 consisting of a dithienopyrrole A novel donor-acceptor dyad, 4, in which the conjugated oligothiophene donor is covalently connected to fullerene PC 71 BM by a flexible alkyl ester linker, is synthesized and applied as photoactive layer in solution-processed single-material organic solar cells (SMOSCs). Excellent photovoltaic performance, including a high short-circuit current density (J SC ) of 13.56 mA cm −2 , is achieved,...

No abstract

Heteroacenes developed to widely used building blocks in organic semiconductors for application in organic electronics due to their tunable structures and properties concomitant with inherent stability. Here, we report efficient preparation and investigation of so far unknown heterotriacenes, basic anti-and syn-dithienopyrazine 5 and 6. The comparison of the two isomers with respect to electronic properties and follow-up reactions gives insights into structure-property and -reactivity relationships. Examples of transition metal-catalyzed CÀ C crosscoupling reactions of corresponding halogenated derivatives show the practical impact for extended π-conjugated systems applied in optoelectronic devices.

A novel and versatile method for the N‐arylation of dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) is presented. By Pd‐ or Cu‐catalyzed coupling a variety of arenes and acenes were directly attached at the DTP−nitrogen yielding a variety of functionalized DTPs. Investigations on optical and redox properties led to valuable structure‐property relationships, which were corroborated by quantum chemical calculations. Further functionalization and elongation of the conjugation of an acceptor‐substituted DTP was elaborated to result in complex cruciform‐type donor−acceptor oligomers, which were investigated and implemented in single material organic solar cells.

Ambifunctional heterpentacenes with the heteroatom sequence SSNSS in the ladder-type backbone were used either as donor or as nonfullerenic acceptor in solutionprocessed bulk-heterojunction solar cells. Different acceptor moieties and side chains were inserted. Synthesis and characterization of the systematically varied structural motifs provided insight in structure-property relationships. Moreover, a dimeric heteroacene was synthesized, and the optoelectronic properties were compared to those of its monomeric counterpart.