Dresden 2026 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
O: Fachverband Oberflächenphysik
O 82: Focus Session: Unoccupied States by Inverse Photoemission III
O 82.5: Talk
Thursday, March 12, 2026, 12:00–12:15, WILL/A317
Effects of Crystallization on the Electronic Structure of Discrete Oligomers — •Alexander Ehm1, Rukiya Matsidik2, Michael Sommer2, and Dietrich R. T. Zahn1 — 1Semiconductor Physics and Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), TU Chemnitz, Chemnitz, Germany — 2Polymer Chemistry, TU Chemnitz, Chemnitz, Germany
Recently, organic photovoltaic cell efficiency surpassed the 20 % landmark, thanks to the development and improved crystallinity of non-fullerene acceptor (NFA) molecules and suitable polymer donors [1]. Low exciton binding energies (EBE), measured by the difference of the transport gap and the optical bandgap, were attributed as key factors in such improvements [2].
Photoemission and low-energy inverse photoemission spectroscopy (PES and LEIPES) in combination directly measure the transport gap. However, challenges are posed by their surface sensitivity in conjunction with the solution processing, low conductivity and radiation sensitivity of thin films of large organic molecules.
Here, we address strategies to avoid surface contamination and charging effects, while investigating the interfacial electronic structure of conjugated discrete oligomer films [3] spin-coated on Ag substrates. Their thermal crystallization reduced their bulk EBE to < 0.1 eV.
[1] F. Furlan, N. Gasparini, Nat. Mater. 24, 336 (2025)
[2] A. Sugie et al., J. Phys. Chem. Lett. 14, 11412 (2023)
[3] R. Matsidik et al., J. Am. Chem. Soc. 145, 8430 (2023)
Keywords: non-fullerene acceptor; inverse photoemission spectroscopy; organic photovoltaic; NDI-T2 oligomers