3D Printing of Arbitrary Perovskite Nanowire Heterostructures

Deterministic integration of arbitrary semiconductor heterostructures opens a new class of modern electronics and optoelectronics. However, the realization of such heterostructures continues to suffer from impracticality, requiring energy- and labor-intensive, time-consuming fabrication processes. Here a 3D printing approach to fabricate freestanding metal halide perovskite nanowire heterostructures with a high degree of control over shape and composition is demonstrated. These features arise from freeform guiding of evaporation-driven perovskite crystallization by a femtoliter precursor meniscus formed on a printing nozzle. By using a double-barreled nanopipette as a printing nozzle, "all-at-once" heterostructure fabrication is achieved within seconds. The 3D-printed perovskite nanowire heterojunctions with multiple emission colors provide exciting optical functionalities such as programmable color mixing and encryption at the single nanopixel level. This "lithography-free" additive approach opens up the possibility to freely design and realize heterostructure-based devices without the constraints of traditional manufacturing processes.