Sr6(Li2Cd)A4S16(A = Ge, Sn): How to Go beyond the Band Gap Limitation via Site-Specific Modification

Band gap tuning is at the core of current optical and electronic device applications, the wide-band-gap chalcogenides are especially challenging and highly desired in many fields, such as nonlinear optical materials. On the basis of our in-depth investigation on the complicated cubic AII6(BI2CII)DIV4S16family, we reveal that the structural complexity causes the band gap tuning to be determined by multiple factors, in which a “bucket effect” is uncovered. Guided by such a bucket effect strategy, we rationally synthesized two new members, Sr6(Li2Cd)A4S16(A = Ge (1; a= 13.916 Å), Sn (2; a= 14.237 Å), via a site-specific substitution. 1exhibits the widest band gap (3.8 eV) in this family known to date. Benefiting from their wide band gaps, 1and 2exhibit excellent laser irradiation duration capability, with laser-induced damage thresholds (LIDTs) of 55.5 and 44.4 MW/cm2at a 1.064 μm incident laser, which are 21 and 17 times higher than that of the benchmark AgGaS2(2.69 MW/cm2). Especially, the LIDT of 1is the highest known to date among the cubic AII6BI2CIIDIV4S16family. Our insight into the band gap tuning in a complex system should shed useful light on the future design of functional materials and band gap engineering.