Indeno[1,2-b]thiophene End-capped Perylene Diimide: Should the 1,6-Regioisomers be systematically considered as a byproduct? - Archive ouverte HAL
Article Dans Une Revue Scientific Reports Année : 2020

Indeno[1,2-b]thiophene End-capped Perylene Diimide: Should the 1,6-Regioisomers be systematically considered as a byproduct?

Pablo Simón Marqués
Francesco Tintori
  • Fonction : Auteur
José María Andrés Castán
  • Fonction : Auteur
Pierre Josse
  • Fonction : Auteur
Clément Dalinot
  • Fonction : Auteur
  • PersonId : 992292
Magali Allain
Philippe Blanchard
Clément Cabanetos

Résumé

Usually considered as a byproduct, the 1,6-dibrominated PDI has rarely been functionalized for the preparation of electro-active conjugated molecules, particularly in the field of organic photovoltaics. In light of the literature, one can ask oneself: Does a 1,7-isomer based functional molecule systematically perform better than its 1,6-analogue? To answer this question, we report herein the synthesis and direct comparison of two indeno[1,2-b]thiophene (IDT) end-capped perylene diimide regioisomers (PDI) (1,6 and 1,7) used as non-fullerene acceptors in organic solar cells. It turned out that in our case, ie, when blended with the well-known PTB7-Th donor polymer, higher performance was reached for devices made with the 1,6-analogue. Major contributors to the recent resurgence of organic photovoltaics (OPVs) 1-3 , molecular non-fullerene accep-tors (NFAs) have driven up power conversion efficiencies (PCEs), in a short amount of time, from "what a fuller-ene derivative does best" 4,5 to more than 15% 6-8. Although these records were reached with indacenodithiophene derivatives, perylene diimides (PDIs) have always held an important place among the electron transporting materials due to their excellent thermal, chemical and photochemical stabilities combined with their singular optical, redox and charge transport properties 9,10. Nonetheless, the PDI extended π-conjugated structure typically suffers from an excessive π-π stacking tendency, forming micrometer-sized crystallites that are detrimental for an efficient charge separation in bulk heterojunction (BHJ) solar cells 11-14. To tackle this problem, important efforts have been devoted to functionalize the peripheral positions, namely the bay (1,6,7,12) and ortho positions (2,5,8,11) 3,9,15-18 , leading to profuse design principles and above all, to a better understanding of the structure-property relationships (Fig. 1) 19-28. The key reaction, the dibromination of the bay positions, holds a special place by providing a precursor to many published molecular and macromolecular π-functional PDI based materials, namely the 1,7-isomer 29. Also generated during the reaction, but in smaller ratio, the 1,6-isomer has not triggered such interest. Conversely, the latter has even motivated the development of purification procedures and methods since usually considered as an impurity 30. As a result, only limited studies aiming at comparing the properties of molecular architectures based on both regioisomers have been reported so far 31-33 , particularly in the field of OPVs. In fact, and to the best of our knowledge , only one paper can be found where the two bromo isomers (1,6 and 1,7) were functionalized either by triphenylamine (TPA) or benzodithiophene (BDT) moieties for the preparation of NFAs 34. In all cases, best PCEs (ca 0.67%) were reached with the 1,7-isomers once blended with different donor polymers and attributed to a better phase separation. Considering the scarcity of reported examples, it would be unthinkable to draw meaningful conclusions on the systematic use of one isomer over the other.

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hal-02888766 , version 1 (05-11-2020)

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Pablo Simón Marqués, Francesco Tintori, José María Andrés Castán, Pierre Josse, Clément Dalinot, et al.. Indeno[1,2-b]thiophene End-capped Perylene Diimide: Should the 1,6-Regioisomers be systematically considered as a byproduct?. Scientific Reports, 2020, 10 (1), ⟨10.1038/s41598-020-60012-7⟩. ⟨hal-02888766⟩
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