Facile C–H iodination of electron deficient benzodithiophene-S,S-tetraoxide for the development of n-type polymers

Abstract

A facile functionalization of the electron-poor building block, benzo[1,2-b:4,5-b0] dithiophene-1,1,5,5-tetraoxide (BDTT) by C–H iodination reaction has been reported. This functionalization opens a new avenue to incorporate this electron-deficient moiety into conjugated systems for organic semiconductors (OSCs). Two novel donor–acceptor conjugated polymers (PBDTT-Th and PBDTT-BDT) were synthesized at high yields by incorporating this functionalized BDTT moiety as an acceptor unit, and thiophene and benzodithiophene as donor units respectively. Though both polymers showed similar LUMO energy levels, the HOMO level of PBDTT-BDT (−5.47 eV) was higher than PBDTT-Th (−5.74 eV), due to the presence of the strong electron donating nature of benzodithophene as compared to thiophene. Both polymers showed electron accepting behavior, which was probed by performing fluorescence quenching experiments with the donor material P3HT. Furthermore, the space charge limited current (SCLC) method using Mott–Gurney law was carried out to determine the electron mobility of PBDTT-Th and PBDTT-BDT, which were found to be 6.26 × 10⁻⁴ and 7.67 × 10⁻⁴ cm² V⁻¹ s⁻¹ respectively.