Crystallization, the phenomenon that transforms disordered atoms or molecules into ordered solid-state structures, is an immensely studied process. However, while researchers have made significant strides in controlling the nucleation of crystals from precursor solutions, directing their subsequent growth to form defect-free single crystals with tailored shapes has proven far more challenging. This limitation has been particularly problematic for materials like halide perovskites, where controlling the formation of defects results in better photoelectric properties. Conventional techniques like inverse temperature crystallization or antisolvent vapor-assisted crystallization allow some control over average growth conditions, but their ability to pattern arbitrary single-crystal geometries while suppressing defect formation has remained confined.
Now, researchers at Tsinghua University have demonstrated optofluidic crystallithography (OCL), a novel approach that leverages a laser as a precise "pen" to simultaneously control the shape and quality of single-crystal halide perovskites as they grow from solution at record speeds.
The scientists used a laser beam to manipulate the molecular motion in the native precursor environment and create inhomogeneous spatial distribution of the molecular species. Harnessing the coordinated effect of laser-controlled local supersaturation and interfacial energy, they precisely steered the ionic reaction at the growth interface and directly printed arbitrary single crystals of halide perovskites of high surface quality, crystallinity, and uniformity at a high printing speed of 102 μm s−1.
The OCL technique can be potentially extended to the fabrication of single-crystal structures beyond halide perovskites, once crystallization can be triggered under the laser-directed local supersaturation. Looking forward, the researchers anticipate that OCL's unprecedented control over crystal formation will impact numerous arenas. Its ability to rapidly map composition-structure-property relationships in multidimensional perovskite libraries may transform materials discovery, while the printing of device-integrated single-crystal components could disrupt optoelectronic manufacturing. The prospect of continuous roll-to-roll printing of wafer-scale single-crystal semiconductors further highlights OCL's disruptive potential.
