SPECTROSCOPY AND UP-CONVERSION MECHANISMS OF CSCDBR3-DY3+

The upconversion luminescence of a Dy3+-doped system is presented and analyzed. CsCdBr3:x% Dy3+ (x = 0.2,1,5) was synthesized and grown as c rystals using the Bridgman technique. Dy3+ ions preferentially enter t his host as charge-compensated dimers. Due to the low-phonon energy th e efficiency of multiphonon-relaxation processes is significantly redu ced in this host compared to oxides and fluorides. Yellow-green upconv ersion luminescence originating from F-4(9/2) can be induced upon exci tation into F-6(5/2) or F-6(3/2) in the near infrared (NIR). Depending on the excitation wavelength, upconversion occurs by an energy-transf er or excited-state absorption mechanism. The two are distinguished by their temporal behavior after an excitation pulse. Analysis of the up conversion-luminescence transient of CsCdBr3:0.2% Dy3+ at 10 K leads t o a rate constant W-t=165 s(-1) for the energy-transfer step. This is very small, and thus upconversion based on one excitation wavelength i s inefficient. In addition, the intermediate NIR level F-6(5/2) is sig nificantly depopulated by multiphonon relaxation at room temperature. [S0163-1829(98)02208-5].