Self-aligned CH3NH3PbBr3 perovskite nanowires via dielectrophoresis for gas sensing applications

• Morphological evolution of MAPbBr 3 nanocubes to nanowires. • Self-alignment of single-crystalline MAPbBr 3 nanowires. • MAPbBr 3 channels exhibits the highest sensitivity for H 2 S gas molecules. • Adsorbed O 2 molecules determine the MAPbBr 3 response to the environmental species. Metal halide perovskites (MHPs) with environment-dependent optoelectronic properties can provide a new platform for highly sensitive and active gas sensor materials. While MHPs are a crystalline semiconductor with high carrier mobility and long carrier diffusion length, the formation of efficient channels for charge carriers can be hindered by the intrinsic point defects and impurities as well as grain boundaries in the solution-cast films with an uncontrolled morphology. Furthermore, a precise control of nanostructured MHP materials and their distribution with respect to device electrodes still remains challenging, which requires tedious efforts for additional fabrication. Herein, we demonstrate that the dielectrophoresis process can allow for self-alignment of single-crystalline MHP nanowires (NWs) with a uniform spatial distribution and orientation on interdigitated electrodes. We found that MAPbBr 3 NWs array sensors exhibited the highest sensitivity (∼120% and τ = 40 s at 100 ppm) for H 2 S gas molecules among oxidizing (NO 2 ) and reducing gases (NH 2 and H 2 S), whereas no significant response was observed for MAPbCl 3 NWs. The MAPbBr 3 NW array-based sensor showed a long time stability exceeding one month with less than 20% derivation during first two weeks. The characteristic response of MHP NWs array significantly depends on the interaction of oxygen molecules adsorbed at their surface with the environmental target species, in which their surface conductivity can be modulated by the variation of trap states related to surface defects. Our work demonstrates a simple and facile route to synthesis and self-alignment of MHP NWs for chemiresistive gas sensors, broadening the range of technological applications of MHPs. Single-crystalline MAPbBr 3 and MAPbCl 3 NWs with high surface area and characteristic surface moieties provide not only distinct optoelectronic properties but also strong and abundant analyte adsorption sites. Self-alignment of single-crystalline MAPbBr 3 nanowires via dielectrophoresis provides a potential platform for chemiresistive gas sensors with high selectivity owing to their atmosphere-dependent electrical properties associated with the intermolecular interactions in the reversible adsorption and desorption process.