Polymer-Assisted Nanoimprinting for Environment- and Phase-Stable Perovskite Nanopatterns.

Despite the great interest in inorganic halide perovskites (IHPs) for a variety of photoelectronic applications, environmentally robust nanopatterns of IHPs have hardly been developed mainly owing to the uncontrollable rapid crystallization or temperature and humidity sensitive polymorphs. Herein, we present a facile route for fabricating environment- and phase-stable IHP nanopatterns over large areas. Our method is based on nanoimprinting of a soft and moldable IHP adduct. A small amount of poly(ethylene oxide) was added to an IHP precursor solution to fabricate a spin-coated film that is soft and moldable in an amorphous adduct state. Subsequently, a topographically prepatterned elastomeric mold was used to nanoimprint the film to develop well-defined IHP nanopatterns of CsPbBr and CsPbI of 200 nm in width over a large area. To ensure environment- and phase-stable black CsPbI nanopatterns, a polymer backfilling process was employed on a nanopatterned CsPbI. The CsPbI nanopatterns were overcoated with a thin poly(vinylidene fluoride--trifluoroethylene) (PVDF-TrFE) film, followed by thermal melting of PVDF-TrFE, which formed the air-exposed CsPbI nanopatterns laterally confined with PVDF-TrFE. Our polymer backfilled CsPbI nanopatterns exhibited excellent environmental stability over one year at ambient conditions and for 10 h at 85 °C, allowing the development of arrays of two-terminal, parallel-type photodetectors with nanopatterned photoactive CsPbI channels. Our polymer-assisted nanoimprinting offers a fast, low-pressure/temperature patterning method for high-quality nanopatterns on various substrates over a large area, overcoming conventional costly time-consuming lithographic techniques.