Perovskites have high potential for future electronic devices, in particular, in the field of opto-electronics. However, the electronic and optic properties of these materials highly depend on the morphology and thus on the preparation; in particular, highly crystalline layers with large crystals and without pinholes are required. Here, nanoimprint is used to improve the morphology of such layers in a thermal imprint step. Two types of material are investigated, MAPbI3 and MAPbBr3, with MA being methylammonium, CH3NH3+. The perovskite layers are prepared from solution, and the crystal size of the domains is substantially increased by imprinting them at temperatures of 100–150 °C. Although imprint is performed under atmospheric conditions which, in general, enhances the degradation, the stamp that covers the layer under elevated temperature is able to protect the perovskite largely from decomposition. Comparing imprinting experiments with pure annealing at a similar temperature and time proves this. Furthermore, imprint is capable of patterning the surface of the perovskite layers; lines and spaces of 150 nm width were reproducibly obtained under imprint at 150 °C. Moreover, a through-layer patterning is possible by using the partial cavity filling approach. Although not yet optimized, this simple way to define isolated perovskite patterns within a layer simply by thermal nanoimprint is of impact for the preparation of devices, as patterning of perovskite layers by conventional techniques is limited.

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Flexible stamps are common for roll-to-roll processing but less common with planar processing, although they offer a number of benefits as, e.g., an improved conformal contact at reduced pressure. A simple way to realize such a flexible stamp is to use a two layer system with a structured top layer and a flexible backplane. The structured top layer is most easily obtained by molding, the backplane provides the flexibility envisaged. For use in a thermal nanoimprint process, a high thermal stability is required for both. This investigation addresses the preparation of flexible composite stamps with OrmoStamp as the structured top layer and polyimide as the flexible backplane. The process recommended for stamp preparation with OrmoStamp has to be modified to avoid bending after the hard bake that is required after ultraviolet-curing of the material to obtain a high stability of the top layer. Reduction of bending is advised, in particular, for large area stamps, where the hard bake step is in conflict with preparation of a flat stamp and limits applicability for thermal nanoimprint. A small scale almost flat flexible composite stamp is prepared and employed for low-pressure nanoimprint; it provides full area imprint at a reduced pressure of 25 bar. The replicated structures, lines of 300 nm, are of high quality and image the stamp structures. Stamps prepared in this way allow a tuning of the flexibility simply by changing the thickness of the backplane.

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