Regensburg 2025 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Energy Storage and Batteries II

CPP 40.1: Talk

Friday, March 21, 2025, 09:30–09:45, H34

Nanoscale Agglomeration Mechanisms of BF-DPB:BPyMPM Donor-Acceptor Systems for Organic Optoelectronic Devices — •Milena Merkel¹, Philipp Wiesener¹, Robert Schmidt¹, Rishi Shivhare^2,3, Rudolf Bratschitsch¹, Saeed Amirjalayer⁴, Koen Vandewal^2,3, and Harry Mönig¹ — ¹Physikalisches Institut, Münster University, Münster, Germany — ²Institute for Materials Research (imo-imomec), Hasselt University, Hasselt, Belgium — ³imec, imo-imomec, Diepenbeek, Belgium — ⁴Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany

The molecular order of photo-active molecules of organic optoelectronic devices has major impact on their performance. However, it is usually investigated only by indirect measurements or simulations. Here we use low-temperature scanning probe microscopy to image the molecular assembly and interfaces of the donor and acceptor molecules BF-DPB and BPyMPM with submolecular resolution. We illustrate the crucial effect of the substrate and the position of the nitrogen atoms in the BPyMPM molecules on the formation of intermolecular C-H..N hydrogen bonds, metal coordination bonds and corresponding self-assemblies. Using scanning tunneling spectroscopy, we are able to correlate the increasing disorder at the BF-DPB:BPyMPM interface with an increase in the HOMO-LUMO gap of BF-DPB. Photoluminescence measurements on BF-DPB indicate a significant increase in intersystem crossing due to molecule-substrate interactions. Our results provide new insights for a tailored design of active molecules and contact layers for organic optoelectronic devices.

Keywords: Organic solar cells; Molecular assembly; Scanning tunneling microscopy; Hydrogen bonds; Metal coordination bonds