Side-Chain Engineering Controls Molecular Packing and Vertical Electron Transport in Discrete n-Type NDI-T2 Oligomers
Abstract
High-efficiency vertical charge transport in multilayer organic optoelectronic devices highly depends on molecular structure and arrangement. Using two T2-(NDI-T2)2 conjugated oligomers with ethylhexyl (EH) and octyldodecyl (OD) side chains as a model system, their effects on electron transport are investigated using, among other techniques, atomic force microscopy (AFM), conductive atomic force microscopy (C-AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS), steady-state optical spectroscopy, and time-dependent density functional theory (TDDFT) calculations. The oligomers of both materials exhibit relatively disordered structures in the as-cast state, whereas annealing enhances structural order and leads to side-chain-dependent changes in molecular stacking. EH-based films show a smaller annealing-induced photoluminescence shift than OD-based films, suggesting less pronounced stacking and conformational rearrangements, consistent with TDDFT-supported exciton analysis. The current-voltage characteristics are analyzed using the space-charge-limited current (SCLC) model. After annealing, both materials exhibit improved vertical electron mobility. The EH-based films reach a maximum mobility of 1.2 x 10^-4 cm^2 V^-1 s^-1. The combined results suggest that the shorter EH side chains modify the out-of-plane packing environment and facilitate vertical electron transport. These results establish a structure-property relationship between side-chain structure, molecular order, exciton coupling and vertical mobility, providing a molecular design basis for optimising organic semiconductors through side-chain engineering.
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BibTeX
@misc{liu2026sidechain,
title = {{Side-Chain Engineering Controls Molecular Packing and Vertical Electron Transport in Discrete n-Type NDI-T2 Oligomers}},
author = {Zihao Liu and Hajar Komekoz and Nisarg Trivedi and Max Dorfner and Lokesh Rasabathina and Rico Ehrler and Mike Hambsch and Chen Wang and Dietrich R. T. Zahn and Jörg Matysik and Stefan C. B. Mannsfeld and Carsten Deibel and Olav Hellwig and Frank Ortmann and Michael Sommer and Georgeta Salvan},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32456},
eprint = {2610.32456},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32456},
}
RIS
TY - UNPB
TI - Side-Chain Engineering Controls Molecular Packing and Vertical Electron Transport in Discrete n-Type NDI-T2 Oligomers
AU - Zihao Liu
AU - Hajar Komekoz
AU - Nisarg Trivedi
AU - Max Dorfner
AU - Lokesh Rasabathina
AU - Rico Ehrler
AU - Mike Hambsch
AU - Chen Wang
AU - Dietrich R. T. Zahn
AU - Jörg Matysik
AU - Stefan C. B. Mannsfeld
AU - Carsten Deibel
AU - Olav Hellwig
AU - Frank Ortmann
AU - Michael Sommer
AU - Georgeta Salvan
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32456
UR - https://arxiv.org/abs/2610.32456
AB - High-efficiency vertical charge transport in multilayer organic optoelectronic devices highly depends on molecular structure and arrangement. Using two T2-(NDI-T2)2 conjugated oligomers with ethylhexyl (EH) and octyldodecyl (OD) side chains as a model system, their effects on electron transport are investigated using, among other techniques, atomic force microscopy (AFM), conductive atomic force microscopy (C-AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS), steady-state optical spectroscopy, and time-dependent density functional theory (TDDFT) calculations. The oligomers of both materials exhibit relatively disordered structures in the as-cast state, whereas annealing enhances structural order and leads to side-chain-dependent changes in molecular stacking. EH-based films show a smaller annealing-induced photoluminescence shift than OD-based films, suggesting less pronounced stacking and conformational rearrangements, consistent with TDDFT-supported exciton analysis. The current-voltage characteristics are analyzed using the space-charge-limited current (SCLC) model. After annealing, both materials exhibit improved vertical electron mobility. The EH-based films reach a maximum mobility of 1.2 x 10^-4 cm^2 V^-1 s^-1. The combined results suggest that the shorter EH side chains modify the out-of-plane packing environment and facilitate vertical electron transport. These results establish a structure-property relationship between side-chain structure, molecular order, exciton coupling and vertical mobility, providing a molecular design basis for optimising organic semiconductors through side-chain engineering.
ER -