Contact Transfer Epitaxy of Halide Perovskites

Halide perovskite materials are very exciting because of their excellent optoelectronic properties and simple deposition with both solution and vapor-phase methods. Until now, solution deposition has received more attention, but there are growing indications that residual solvent may limit performance and in particular long-term stability. Evaporation is a promising alternative, but is more complicated to implement; it requires vacuum, multiple sources at different temperatures, is difficult to switch between different materials due to cross-contamination and typically leads to films with very small grain size. Here a novel contact transfer method is presented for fabricating single crystalline perovskites that maintains the simplicity and flexibility of solution deposition while avoiding the use of solvent. This contact transfer epitaxy method uses an acceptor substrate consisting of self-assembled perovskite nanocubes to control crystal orientation and a donor substrate of the desired perovskite film to determine the ultimate composition. By heating the two substrates under close contact in atmospheric conditions, the perovskite film is transferred from the donor to the acceptor substrate, showing cubic phase (100) orientation even with hexagonal donor films. It is shown that contact transfer epitaxy is compatible with a variety of compositions and does not require specialized evaporators or vacuum conditions.