Sub‐30 nm 2D Perovskites Patterns via Block Copolymer Guided Self‐Assembly for Color Conversion Optical Polarizer

Abstract Despite the remarkable advances made in the development of 2D perovskites suitable for various high‐performance devices, the development of sub‐30 nm nanopatterns of 2D perovskites with anisotropic photoelectronic properties remains challenging. Herein, a simple but robust route for fabricating sub‐30 nm 1D nanopatterns of 2D perovskites over a large area is presented. This method is based on nanoimprinting a thin precursor film of a 2D perovskite with a topographically pre‐patterned hard poly(dimethylsiloxane) mold replicated from a block copolymer nanopattern consisting of guided self‐assembled monolayered in‐plane cylinders. 1D nanopatterns of various 2D perovskites (A′ ₂ MA _{n −1} Pb _n X _{3 n +1} ,A′ = BA, PEA, X = Br, I) are developed; their enhanced photoluminescence (PL) quantum yields are approximately four times greater than those of the corresponding control flat films. Anisotropic photocurrent is observed because 2D perovskite nanocrystals are embedded in a topological 1D nanopattern. Furthermore, this 1D metal‐coated nanopattern of a 2D perovskite is employed as a color conversion optical polarizer, in which polarized PL is developed. This is due to its capability of polarization of an incident light arising from the sub‐30 nm line pattern, as well as the PL of the confined 2D perovskite nanocrystals in the pattern.