Abnormal bandgap enlargement resulted in a promising mid-infrared nonlinear optical material Rb2CdBrI3 with an ultrahigh laser damage threshold

Abstract

The low laser damage threshold of commercial infrared nonlinear optical materials is the main bottleneck that hinders their high-power coherent source applications. Here, a new compound Rb₂CdBrI₃ was successfully synthesized in a controlled manner by using a rational halogen substitution. It features a zero-dimensional [CdBrI₃]²⁻ tetrahedron and inserted Rb⁺ cations were used as the counter cations. In contrast to the isomorphic Rb₂CdBr₂I₂, Rb₂CdBrI₃ exhibits an anomalously enlarged bandgap of 4.01 eV and an unprecedented high laser damage threshold up to 46 times that of AgGaS₂. Theoretical calculations determine that the abnormal bandgap attributes to weak conduction band dispersion from the reduced net dipole moment and the enhanced halogen s–p orbital mixing when Br is replaced by I. This work not only promotes Rb₂CdBrI₃ as a promising infrared nonlinear converter, but also supplies new modulating viewpoints for the band-sensitive optoelectronic devices, such as hybrid perovskite solar cells with mixed halogen.