We report the synthesis and systematic investigation of nine different indigo derivatives as promising materials for sustainable organic electronics. It has been shown that chemical design allows one to tune optoelectronic properties of indigoids as well as their semiconductor performance in OFETs. Fundamental correlations between the molecular structures of indigo derivatives, structural characteristics of their films, charge carrier transport properties and transistor characteristics have been revealed. Particularly important was lowering the LUMO energy levels of indigoids bearing strong electron withdrawing groups which improved dramatically ambient stability of n-type OFETs. Chemical structures of novel indigoids enabling truly air-stable n-channel OFET operation were proposed.

We report the synthesis and comparative study of five conjugated polymers P1-P5 with different arrangements of two solubilizing 2-ethlyhexyl side chains in their repeating units. It has been shown that positioning of the alkyl substituents affects strongly frontier energy levels of the polymers and results in variation of their optical band gaps between 1.65 and 2.0 eV. The highest (2.8×10 -4 cm 2. V -1. s -1 ) and the lowest (2.4×10 -5 cm 2. V -1. s -1 ) charge carrier mobilities determined for the polymers P1 and P5, respectively, using SCLC technique differ by more than one order of magnitude. GIWAXS measurements also revealed very different degrees of molecular ordering in the films of polymers P1-P5 which correlate well with the SCLC mobility data and solid state photoluminescence spectra of these materials. The bulk heterojunction solar cells based on the composites of polymers P1-P5 with [60]PCBM demonstrated power conversion efficiencies ranging from 0.6% (P5) to 5.1% (P1) thus evidencing strong influence of the alkyl side chains on the photovoltaic performance of the designed polymer-based materials. This journal is Electronic Supplementary Information (ESI) available: Optical absorption spectra for thin films, cyclic voltammograms, J 1/2 -V plots for hole-only This journal is ARTICLE Journal Name devices, 2D GIWAXS patterns for thin films of P1-P5, AFM images for composites of P1-P5 with [60]PCBM. See

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