New Molecular Design, Step-Saving Synthesis, and Applications of Indolocarbazole Core-Based Oligo(hetero)arenes.

ABSTRACT

In this work, we have successfully synthesized 15 new examples (LLA01-06; LinLi01-10) of small-molecule hole-transporting materials (HTM) using the less explored indolocarbazole (ICbz) as core moiety. Different from previously reported ICbz HTMs, LinLi01-10 exhibit new molecular designs in which 3,4-ethylenedioxythiophene (EDOT) units are inserted as crucial π-spacers and fluorine atoms are introdcued into end-group molecules. These substantially improve the materials solubility and device power conversion efficiencies (PCEs) while fabricated in perovskite solar cells (PSC). More importantly, LinLi01-10 are generated by a sustainable synthetic approach involving the use of straightforward C-H/C-Br couplings as key transformations, thus avoiding additional synthetic transformations including halogenation and borylation reactions called substrate prefunctionalizations usually required in Suzuki reactions. Most HTM molecules can be purified simply by reprecipitations instead of conducting column chromatography. In contrast to LLA01-06 without additional EDOT moieties, PSC devices using LinLi01-10 as hole-transport layers display promising PCEs of up to 17.5 %. Interestingly, PSC devices employing seven of the LinLi01-10 as hole-transport molecules, respectively, are all able to show an immediate >10 % PCE (t=0) without any device oxidation/aging process that is necessary for the commercial spiro-OMeTAD based PSCs.