Layered-Perovskite Nanowires with Long-Range Orientational Order for Ultrasensitive Photodetectors.

2D layered metal-halide perovskites combine efficient exciton radiative recombination in crystal interior with long-distance free-carrier conduction at layer edges, which are promising candidates for realizing high-performance photovoltaic, light-emission and photodetection devices. The anisotropic electrical conductivity in layered perovskites imposes an additional requirement of orientational control for enabling favorable charge transport. However, rational fabrication of single-crystalline nanostructures with pure crystallographic orientation is still elusive. Herein, large-scale pure (101)-orientated 2D-perovskite single-crystalline nanowire arrays are realized by combining solvent engineering with the capillary-bridge lithography technique. Ordered nucleation at liquid-air interface and unidirectional growth along the dewetting direction are demonstrated by fluorescence microscopy and grazing-incidence X-ray scattering in discrete capillary bridges. In consideration of crystal interior exhibiting high resistance arising from the serial insulating organic barriers and ultrafast dissociation of excitons to generate long-lived free carriers at layer edges, ultrasensitive photodetectors are demonstrated with average responsivity exceeding 1.1 × 10 A W and detectivity exceeding 9.1 × 10 Jones.