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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 36: Organic Electronics and Photovoltaics III
CPP 36.2: Talk
Thursday, March 21, 2024, 09:45–10:00, H 0110
Energetic landscape of fluorinated and non-fluorinated donors and non-fullerene acceptors in bulk heterojunction organic photovoltaics — Shahidul Alam1, Jafar I. Khan2, Vojtech Nádaždy3, Tomáš Váry3, Aurelien D. Sokeng4, Md Moidul Islam4, Christian Friebe4, Wejdan Althobaiti1, Wenlan Liu5, Martin Hager4, Ulrich S. Schubert4, Carsten Deibel6, Denis Andrienko5, Frédéric Laquai1, and •Harald Hoppe4 — 1KAUST, Saudi Arabia — 2University of Hull, UK — 3Slovak Academy of Sciences, Slovak Republic — 4IOMC/CEEC, Jena, Germany — 5MPIP, Mainz, Germany — 6TU Chemnitz, Germany
Performance improvement of OSCs via fluorination of the D and/or NFA is an effective method. The end-group fluorination of the well-known NFA ITIC yields further extension of the absorption to the NIR, which increases the SC's Jph compared to the non-fluorinated version. Herein, ITIC and two of its fluorinated variants were synthesized and systematically investigated concerning the influence of end-group fluorination on physicochemical, optical, and photovoltaic properties. DFT calculations show that fluorination increases the EA of the acceptor and, therefore, reduces the Voc of the built devices. On the other hand, the molecular quadrupole moment increases with the degree of fluorination leads to more efficient dissociation and reduced recombination of CT-states at the D-A interface. At the same time, IE increases, thus increasing the driving force for CT-state formation. The collected and presented results herein shed light on the importance of the energetic landscape at the D-A interface and how this deviates from general expectations when consulting the pristine materials.