Defective [Bi2O2]2+ Layers Exhibiting Ultrabroad Near-Infrared Luminescence

Graphical Beyond ferroelectricity : The defective [Bi 2 O 2 ] 2+ layers in Aurivillius phases show broadband near-IR luminescence that covers the telecommunication and biological optical windows (see figure). The luminescence was identified to stem from oxygen vacancies and defect complexes. This offers a probe for the examination of defect states in Aurivillius-phase ferroelectrics and possibilities for coupling both physical behaviors. Aurivillius phases have been routinely known as excellent ferroelectrics and have rarely been deemed as materials that luminesce in the near-infrared (NIR) region. Herein, it is shown that the Aurivillius phases can demonstrate broadband NIR luminescence that covers telecommunication and biological optical windows. Experimental characterization of the model system Bi 2.14 Sr 0.75 Ta 2 O 9− x , combined with theoretical calculations, help to establish that the NIR luminescence originates from defective [Bi 2 O 2 ] 2+ layers. Importantly, the generality of this finding is validated based on observations of a rich bank of NIR luminescence characteristics in other Aurivillius phases. This work highlights that incorporating defects into infinitely repeating [Bi 2 O 2 ] 2+ layers can be used as a powerful tool to space-selectively impart unusual luminescence emitters to Aurivillius-phase ferroelectrics, which not only offers an optical probe for the examination of defect states in ferroelectrics, but also provides possibilities for coupling of the ferroelectric property with NIR luminescence.