Triphenylamine-Based Push–Pull σ–C60 Dyad As Photoactive Molecular Material for Single-Component Organic Solar Cells: Synthesis, Characterizations, and Photophysical Properties
A. Labrunie, J. Gorenflot, M. Babics, O. Alévêque, S. Dabos-Seignon, A.H. Balawi, Z. Kan, M. Wohlfahrt, E. Levillain, P. Hudhomme, P.M. Beaujuge, F. Laquai, C. Cabanetos, P. Blanchard
Chemistry of Materials, 30, 10, 3474-3485, (2018)
Molecule engineering, Organic photovoltaics, Single-component organic solar cell, Excited state spectroscopy, Transient absorption spectroscopy, Charge generation, Charge recombination
A push–pull σ–C60 molecular dyad was synthesized via Huisgen-type click chemistry and used as photoactive material for single-component organic solar cells. Steady-state photoluminescence (PL) experiments of the dyad in solution show a significant quenching of the emission of the push–pull moiety. Spin-casting of a solution of the dyad results in homogeneous and smooth thin films, which exhibit complete PL quenching in line with ultrafast photoinduced electron-transfer in the solid state. Spectroelectrochemistry reveals the optical signatures of radical cations and radical anions. Evaluation of the charge carrier mobility by space-charge limited current measurements gives an electron-mobility of μe = 4.3 × 10–4 cm2 V–1 s–1, ca. 50 times higher than the hole-mobility. Single-component organic solar cells yield an open-circuit voltage Voc of 0.73 V and a short-circuit current density of 2.1 mA cm–2; however, a poor fill factor FF (29%) is obtained, resulting in low power conversion efficiency of only 0.4%. Combined transient absorption (TA) and time-delayed collection field (TDCF) experiments show mostly ultrafast photon-to-charge conversion and a small component of diffusion-limited exciton dissociation, revealing the presence of pure fullerene domains. Furthermore, a strong field dependence of charge generation is observed, governing the device fill factor, which is further reduced by a competition between extraction and fast recombination of separated charges.
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