High length-to-width aspect ratio lead bromide microwires via perovskite-induced local concentration gradient for X-ray detection

Abstract

Semiconducting microwires with high length-to-width (L : W) aspect ratio are well suited for electronic and optoelectronic applications. Conventional approaches that first crystallize wires in a solution then mechanically transfer to device-integrable substrates are vulnerable to wire breakage and contamination, resulting in poor reproducibility. Here we introduce a strategy to grow long, thin lead bromide (PbBr₂) microwires with the aid of a gradient. We take advantage of PbBr₂ and methylammonium lead bromide (MAPbBr₃) perovskite co-crystallization to create a local increase in the PbBr₂ to methylammonium bromide (MABr) concentration ratio. We then present the successful growth of well-oriented PbBr₂ microwires over 1 cm in length and as thin as 1.6 μm in diameter, reaching a maximum 5000 L : W ratio under optimized conditions; this value is almost 200 times larger than we found in pure PbBr₂ solution. Structural characterization and elemental composition mapping show no additional phases or impurities present in the dried crystals, and planar-integrated microwires on conductive substrates show an ON/OFF ratio of 10 when exposed to X-ray photons.