Freeform Fabrication of Layered Halide Perovskite Nanowire Heterojunctions

Layered halide perovskites assembled into heterostructures offer precise manipulation of interfaces and electronic structures, making them ideal candidates for a wide range of optoelectronic applications such as photovoltaics, light-emitting diodes, lasers, and photodetectors. Here, we demonstrate freeform fabrication of layered halide perovskite nanowire heterojunctions with programmed geometry and composition. The method utilizes a femtoliter meniscus of precursor solution to draw a path of solution-mediated layered halide perovskite crystallization at will, enabling the deterministic assembly of freestanding, multi-segmented nanowire heterojunctions. The interdiffusion kinetics of halide anions across the layered halide perovskite nanowire heterojunctions have been investigated, revealing suppressed ion migration and enhanced stability compared to their 3D perovskite counterparts. Furthermore, we demonstrate proof-of-concept self-powered photodetectors that exhibit rectification, zero-bias photocurrent, and fast response, directly validating the functional translation of structural programmability. This work establishes femtoliter meniscus-guided nanoprinting as a versatile and scalable platform for programmable optoelectronic nanodevices.