In OSCs in particular, orientation at the solid and vapour interface is important for improving the performance of a variety of devices, with different functionalities requiring different alignments. In organic field-effect transistors (OFETs), for example, charge mobility is greater when molecules are aligned side-on at the solid dielectric interface, as charge transport can occur in the π-stacking direction rather than having to proceed through the often insulating side-chains. Conversely, in organic photovoltaics (OPVs), the face-on orientation at the electron donoracceptor bulk heterojunction (BHJ) interface is favoured as it reduces charge recombination by allowing efficient charge transport away from the interface, while also ensuring better charge generation by increasing donor-acceptor orbital overlap. More specifically, charge separation at the donor-acceptor interface has been shown to be favoured by a displaced planar (slipstacked) molecular arrangement rather than a perfectly stacked (cofacial) arrangement because it leads to weakly bound charge-transfer states that can readily separate but are less susceptible to recombination. Organic light-emitting diode (OLED) performance also depends on the orientation of the emitter's transition dipole moment with respect to the substrate, with planar alignment preferred. The design of molecules for these devices should therefore focus not only on the electronic properties of the individual molecule, but also on how the molecules align at important interfaces in the device in order to maximise performance.