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Organized nano‐ and microstructures of molecular semiconductors display interesting optical and photonic properties, and enhanced charge carrier mobilities, as compared to disordered thin films. However, known directed‐growth and self‐organization strategies cannot create structured molecular heterojunctions and cannot be practically incorporated into existing device fabrication routines to create large‐area optoelectronic devices. Here, an ultrathin (<2 nm) seed layer of the compound coronene creates 1D nanostructures of an electron‐transporting molecule (IFD) is shown, which possesses an intrinsic proclivity to form disordered thin films in the absence of the seed layer. It is revealed that nanostructured IFD films exhibit enhanced light absorption and emission, and greater electron mobilities, as compared to amorphous counterparts. This seed layer strategy creates uniform IFD nanowires over large areas of up to 18 mm²at low processing temperatures. Notably, the coronene seed layer creates IFD nanowires when applied over either oxide surfaces or predeposited organic layers, meaning that this structuring approach can be integrated into diode manufacturing routines to realize large‐area flexible optoelectronic devices. Flexible organic light‐emitting diodes and fullerene‐free organic solar cells containing IFD nanowires in the photoactive layer to demonstrate that molecular nanostructures can lead to robust, large‐area device arrays on flexible substrates being fabricated.

 

Understanding how dipolar, non-centrosymmetric organic semiconductors self-assemble, nucleate, and crystallize is integral for designing new molecular solids with unique physical properties and light-matter interactions. However, dipole–dipole and van der Waals interactions compete to direct the assembly of these compounds, making it difficult to predict how solids are formed from individual molecules. Here, we investigate four small molecules ( TpCPD , TpDCF , AcCPD , and AcDCF ) possessing anisotropic, non-planar structures and large dipole moments, and establish robust algorithms to control their molecular self-assembly via simple physical vapor deposition. Each molecule contains a central polar moiety, consisting of either a cyclopentadienone (CPD, ca. 3.5 D dipole moment) or dicyanofulvene (DCF, ca. 7.0 D dipole moment) core, that is surrounded by either four twisted phenyl (Tp) groups or a fused aromatic (acenaphthene, Ac) ring system. We find that only molecules containing the fused ring system form 1D nanowires due to the stronger van der Waals associations of the long, planar acenaphthene moieties. We examine the kinetics of self-assembly for AcDCF and create diverse 1D morphologies, including both curved and linear nanostructures. Finally, using conductive AFM (c-AFM) measurements, we show that 1D AcDCF wires support higher current densities relative to randomly-oriented clusters lacking long-range order.