Triphenylamine/Tetracyanobutadiene‐Based π‐Conjugated Push–Pull Molecules End‐Capped with Arene Platforms: Synthesis, Photophysics, and Photovoltaic Response

Abstract

Abstract π‐Conjugated push–pull molecules based on triphenylamine and 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) have been functionalized with different terminal arene units. In solution, these highly TCBD‐twisted systems showed a strong internal charge transfer band in the visible spectrum and no detectable photoluminescence (PL). Photophysical and theoretical investigations revealed very short singlet excited state deactivation time of ≈10 ps resulting from significant conformational changes of the TCBD‐arene moiety upon photoexcitation, opening a pathway for non‐radiative decay. The PL was recovered in vacuum‐processed films or when the molecules were dispersed in a PMMA matrix leading to a significant increase of the excited state deactivation time. As shown by cyclic voltammetry, these molecules can act as electron donors compared to C 60 . Hence, vacuum‐processed planar heterojunction organic solar cells were fabricated leading to a maximum power conversion efficiency of ca. 1.9 % which decreases with the increase of the arene size.