Designing a novel perovskite-type KCd(NH2SO3)3 with deep-ultraviolet transparency and strong second-harmonic generation response†

Designing deep-ultraviolet (DUV) nonlinear optical (NLO) materials that simultaneously achieve DUV transparency and strong second-harmonic generation (SHG) remains a significant challenge. Here, we overcome this hurdle by harnessing the versatility of the perovskite (ABX₃) structure to develop a novel DUV NLO crystal. Specifically, we have successfully synthesized a non-centrosymmetric Cd-containing sulfamic compound, KCd(NH₂SO₃)₃, inspired by the perovskite architecture. The strategic incorporation of SO₃NH₂⁻ groups at the X-sites not only induces distorted [CdO₃N₃] octahedra, thereby enhancing the SHG response, but also ensures an ultrawide bandgap, which enables excellent DUV transparency. Consequently, this material exhibits a strong SHG response, approximately 1.1 times that of KH₂PO₄ (KDP), with a DUV cutoff edge below 190 nm. Furthermore, large transparent single crystals (20 × 17 × 5 mm³) can be readily grown via a simple aqueous solution method, underscoring its potential for practical application. This innovative approach offers new design strategies for DUV NLO materials, overcoming the traditional trade-off between SHG response and UV transparency.