1 Department of Chemistry and Biochemistry, Concordia University, 7141 rue Sherbrooke Ouest, H4B?1R6, Montreal, Québec, Canada.
2 Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 rue Sherbrooke Ouest, H4B?1R6, Montreal, Québec, Canada.
3 Centre Énergie Matériaux Télécommunications, Institut national de la recherche scientifique (INRS), 1650 Bd Lionel-Boulet, J3X?1P7, Varennes, Québec, Canada.
4 Department of Physics, Concordia University, 7141 rue Sherbrooke Ouest, H4B?1R6, Montreal, Québec, Canada.
5 Centre for Nanoscience Research (CeNSR), Concordia University, 7141 rue Sherbrooke Ouest, H4B?1R6, Montreal, Québec, Canada.

Molecular p-dopants designed to undergo electron transfer with organic semiconductors are typically planar molecules with high electron affinity. However, their planarity can promote the formation of ground-state charge transfer complexes with the semiconductor host and results in fractional instead of integer charge transfer, which is highly detrimental to doping efficiency. Here, we show this process can be readily overcome by targeted dopant design exploiting steric hindrance. To this end, we synthesize and characterize the remarkably stable p-dopant 2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)acetonitrile) comprising pendant functional groups that sterically shield its central core while retaining high electron affinity. Finally, we demonstrate it outperforms a planar dopant of identical electron affinity and increases the thin film conductivity by up to an order of magnitude. We believe exploiting steric hindrance represents a promising design strategy towards molecular dopants of enhanced doping efficiency.