Mass Production of Gradient Perovskite Nanowires via Microscale Thermal Engineering

The bandgap engineering of halide perovskites at microscopic level is challenging due to fabrication complexity, environmental sensitivity and material stability. Here we report a facile approach to high-yield compositional graded perovskite nanowires (NWs) via vapor-phase anion exchange methods. Using rationally engineered thermal inhomogeneity along the length of single NWs, arrays of NWs with compositional gradient across tens of micrometers can be readily mass-produced via bottom-up as well as top-down exchange strategies. These exchanged NWs exhibit well-preserved single-crystallinity for efficient optical and electrical transport, while their halogen stoichiometry, fluorescence, and energy band structure demonstrate apparent axial gradient. Detailed analysis of elemental distribution and thermal simulation reveal that the ultralow thermal conductivity together with reduced dimensionality leads to microscale temperature gradient, which is further converted to compositional gradient upon anion exchange. In addition, the gradient NWs show excellent optoelectronic features suitable for further integration into functional devices. This work provides guidelines for composition manipulation of perovskites through thermal engineering, extending their applications in ultracompact microspectrometers, spectral imaging sensors, and other miniaturized optoelectronic devices.