Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Organic Electronics and Photovoltaics 3

CPP 40.3: Vortrag

Donnerstag, 8. September 2022, 15:45–16:00, H38

Protonation-Induced Charge Transfer and Polaron Formation in Organic Semiconductors Doped by Lewis Acids — •Fabian Bauch, Chuan-Ding Dong, and Stefan Schumacher — Physics Department and CeOPP, Paderborn University, Germany

Organic electronics rely crucially on doping to enhance the conductivity of organic semiconductors (OSC). Lewis acid doping of OSC is currently of great interest as an alternative to typical molecular p-type doping. Recently, the underlying process was understood to be based on the electron transfer (ET) from a neutral polymer to the protonated polymer [Nat. Mater. 18, 1327 (2019)]. In this work, we provide insight into the microscopic process by investigating the influence of protons on the electronic properties of the copolymer PCPDT-BT using DFT calculations. [1] We find that a single proton on the backbone can give rise to a polaron coupled to the proton position. Two protons on the same polymer backbone can induce a long range intrachain ET, resulting in a polaron decoupled from the proton positions, more fit to act as charge carrier. We also demonstrate the possibility of ET between a neutral polymer and a doubly protonated polymer. The experimental data on the doping of PCPDT-BT via Lewis acid BCF agree well with our simulated vertical excitation spectra for an ensemble of protonated species with increasing amounts of protons. Our results highlight the important role of multiple protonation of the OSC backbone in completing the mechanistic picture of Lewis acid doping. [1] F. Bauch, C. Dong, and S. Schumacher, RSC Advances 12, 13999 (2022).