Abstracts 2001

Abstract of Publication No. 405

Oliver S. Wenger, Rafael Valiente and Hans U. Güdel
Optical spectroscopy of the Ni2+-doped layer perovskites Rb2MCl4 (M = Cd, Mn):
Effects of Ni2+-Mn2+ exchange interactions on the Ni2+ absorption, luminescence, and upconversion properties

Phys. Rev. B 64, 235116/1-8 (2001)      Full Text (PDF)      DOI-Link     

Abstract: Single crystals of Ni2+-doped Rb2CdCl4 and Rb2MnCl4 are studied by polarized optical absorption and luminescence spectroscopy at 15 K. In Ni2+:Rb2MnCl4, Ni2+-Mn2+ exchange interactions, which occur exclusively within the perovskite layers of this material, dramatically affect the absorption, luminescence, and up-conversion properties of Ni2+ for light polarized within the layers (s): The Ni2+ 3A2g 1Eg and 1A1g ground-state-absorption (GSA) transitions are each enhanced by about an order of magnitude when compared to Ni2+:Rb2CdCl4. Similarly, in Ni2+:Rb2MnCl4 the 3T2g 1T2g excited-state absorption (ESA) as well as its reverse luminescence transition experience an intensity enhancement in their electronic origin region in s polarization. One- and two-color up-conversion-excitation experiments show that, due to the in-plane exchange enhancement of the up-conversion-relevant GSA and ESA transitions in Ni2+:Rb2MnCl4, the near-infrared-(NIR) to-visible (VIS) up-conversion process at 15 K in this material is up to a factor of 55 more efficient for s than for p-polarized excitation, and also one to two orders of magnitude more efficient than in Ni2+:Rb2CdCl4 at the same temperature. The structural conditions for efficient Ni2+-Mn2+ exchange interactions are discussed. The NIR-to-VIS up-conversion efficiency can be further enhanced by an energy-transfer step from Ni2+ 1T2g to Mn2+ 4T1g, however, this occurs very inefficiently in Ni2+:Rb2MnCl4.

Last modified: 13.12.11 by Gabriela Frei