Threshold bandgap of lead halide hybrid perovskites for making stable single crystal by NIR laser trapping

Abstract

The remarkable optoelectronic properties of hybrid halide perovskites position them as pivotal materials for the next generation of electronic devices, LEDs, lasers, and solar cells, potentially revolutionizing these technological domains. In this study, we harness the capabilities of contemporary laser trapping technology—a non-contact method for manipulating particles—to elucidate the conditions necessary for stable perovskite crystal formation. Using a 1064 nm near-infrared (NIR) continuous-wave (CW) laser, commonly selected for trapping experiments, we establish the threshold bandgap essential for the stable crystallization of MAPbX3 perovskite crystals. Our research reveals that MAPbI3, with a bandgap of 1.59 eV, undergoes rapid explosive crystallization when subjected to the 1064 nm laser, making it unsuitable for stable crystal growth. In contrast, MAPbBr3 with a bandgap of 2.26 eV forms stable single crystals within 6 min at the air-solution interface, when exposed to the same 1064 nm NIR laser at 1.0 W output power. Notably, a minor reduction in bandgap to 2.23 eV in the mixed halide MAPbBr2.75I0.25 results in an abrupt transition to explosive crystallization. These findings introduce a novel insight into the bandgap dependency for the crystallization process, delineating a threshold bandgap of 2.26 eV for MAPbBr3, below which the crystal growth becomes unstable under a 1064 nm laser. The study provides a significant advancement in the field by defining the precise bandgap necessary for the formation of robust, stable perovskite crystals using laser trapping techniques. This threshold bandgap knowledge is crucial for developing controlled synthesis protocols for perovskites, optimizing their optoelectronic properties for application in modern technologies. Moreover, the investigation suggests that to achieve stable crystallization of perovskites with a bandgap below 2.26 eV, laser trapping with wavelengths longer than 1064 nm may be required, opening new avenues for material processing and device fabrication.