Triphenylamine/Tetracyanobutadiene‐Based π‐Conjugated Push–Pull Molecules End‐Capped with Arene Platforms: Synthesis, Photophysics, and Photovoltaic Response
Résumé
Pi-Conjugated push-pull molecules based on triphenylamine and 1,1,4,4-tetracyanobuta-1,3diene (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 C60. 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.
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