Orientation Engineering in Low-Dimensional Crystal-Structural Materials via Seed Screening.

The orientation of low-dimensional crystal-structural (LDCS) films significantly affects the performance of photoelectric devices, particularly in vertical conducting devices such as solar cells and light-emitting diodes. According to film growth theory, the initial seeds determine the final orientation of the film. Ruled by the minimum energy principle, lying (chains or layers parallel to the substrate) seeds bonding with the substrate through van der Waals forces are easier to form than standing (chains or layers perpendicular to the substrate) seeds bonding with the substrate by a covalent bond. Utilizing high substrate temperature to re-evaporate the lying seeds and preserve the standing seeds, the orientation of 1D crystal-structural Sb2 Se3 is successfully controlled. Guided by this seed screening model, highly [211]- and [221]-oriented Sb2 Se3 films on an inert TiO2 substrate are obtained; consequently, a record efficiency of 7.62% in TiO2 /Sb2 Se3 solar cells is achieved. This universal model of seed screening provides an effective method for orientation control of other LDCS films.