Modification of the band gap of Ruddlesden‒Popper perovskites Srn+1TinO3n+1 (n=1, 2, 3, and ∞) by Fe ion irradiation doping

Ruddlesden‒Popper (RP)-type perovskite materials Srn+1TinO3n+1 (n = 1, 2, 3, and ∞) have important application prospects in photocatalysis. However, their wide band gap limits their visible light absorption ability. Doping is an efficient method that can be used to reduce the band gap and improve its light absorption range. In this work, irradiation doping with the advantages of compulsivity and controllability, rather than a chemical doping method, is used to manipulate the band gaps of Srn+1TinO3n+1 to understand the respective contributions of the substitution of the Sr and Ti sites to the band gap reduction as a function of the n value. The solid-state reaction-prepared RP-type perovskites Srn+1TinO3n+1 (n = 1, 2, 3, and ∞) irradiated by a 270 keV Fe ion beam with 0–1 × 1016 ions/cm2 doses were characterized by SEM, XRD and UV–vis diffuse reflectance spectra. Tauc plot analysis showed that the band gaps of Srn+1TinO3n+1 decreased with an increase in Fe doping dose, which was confirmed by DFT calculations. Meanwhile, the effects of the perovskite and rock-salt layers of the RP-type perovskite on the band gap modification were demonstrated, showing that the band gap of Srn+1TinO3n+1 with smaller n values decreases less when the Fe irradiation dose increases. This is explained by more salt SrO layers found in Srn+1TinO3n+1 for smaller n values, which prevents the substitution of Sr and Ti atoms in perovskite layers, significantly influencing the band gap.