Molecular doping has been shown to improve the performance of various organic (opto)electronic devices. When compared to p-doped systems, research into n-doped organic small-molecules is relatively limited, primarily due to the lack of suitable dopants and the often encountered unfavourable microstructural effects. These factors have prevented the use of n-doping in a wider range of existing materials, such as non-fullerene acceptors (NFAs), that have already shown great promise for a range of (opto)electronic applications. Here, we show that several different molecular n-dopants, namely [1,2-b:2′,1′-d]benzo[i][2.5]benzodiazocine potassium triflate adduct (DMBI-BDZC), tetra-n-butylammonium fluoride (TBAF) and 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (N-DMBI), can be used to n-dope the molecular semiconductor O-IDTBR, a promising NFA, and increase the electron field-effect mobility to >1 cm2 V-1 s-1. By combining complementary experimental techniques with computer simulations of doping and charge carrier dynamics, we show that improved charge transport arises from synergistic effects of n-type doping and morphological changes. Specifically, a new, previously unreported dopant-induced packing orientation results in one of the highest electron mobility values reported to-date for an NFA molecule. Overall, this work highlights the importance of dopant-semiconductor interactions and their impact on morphology, showing that dopant-induced molecular packing motifs may be generic and a key element of the charge transport enhancement observed in doped organics.
KAUST Repository Item: Exported on 2021-04-20
Acknowledgements: The authors acknowledge the King Abdullah University of Science and Technology (KAUST) for financial support. LT acknowledges the use of the GRNET HPC facility ARIS under project STEM-2. This research used CMS beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory
under Contract No. DE-SC0012704. DA received funding from the BMBF grants InterPhase and MESOMERIE (FKZ 13N13661,
FKZ 13N13656) and the European Union Horizon 2020 research and innovation program ‘‘Widening materials models’’ under
Grant Agreement No. 646259 (MOSTOPHOS). D. A. also acknowledges KAUST for hosting his sabbatical. A. M. acknowledges
postdoctoral support of the Alexander von Humboldt Foundation.