Effect of temperature and excitation power on down-conversion process in Tb3+/Yb3+-activated silica-hafnia glass-ceramic films

TL;DR

This study investigates how temperature and excitation power influence the down-conversion process in Tb3+/Yb3+-activated silica-hafnia glass-ceramic films, revealing temperature-dependent emission characteristics and energy transfer mechanisms relevant for photovoltaic applications.

Contribution

It provides new insights into the temperature and power dependence of down-conversion luminescence in Tb3+/Yb3+ doped silica-hafnia glass-ceramics, highlighting mechanisms that enhance photovoltaic efficiency.

Findings

Yb3+ emission intensity and broadening are temperature-dependent

Energy transfer from Tb3+ to Yb3+ involves specific mechanisms

Power dependence spectra reveal details of luminescence processes

Abstract

Transparent glass ceramics, when activated by rare earth ions, are excellent photonic materials. Regarding photonic glass-ceramics based on silicates, hafnia and silica in a binary system has proved to be an excellent matrix to incorporate rare earth ions in the hafnia nanocrystals, resulting in important luminescence enhancement and, consequently, allowing a large spectrum of critical applications. Here we will focus on the downconversion mechanism driven by the couple Tb3+/Yb3+, largely exploited in photovoltaic systems. The research presented here has been performed on 70SiO2-30HfO2 silica-hafnia glass-ceramic films activated with 19 % rare earth ions: [Tb + Yb]/[Si + Hf] = 19 %. Two main results will be discussed: (a) the intensity and the broadening of the Yb3+ emission band at 975 nm were found to be temperature-dependent, as shown in the figure; (b) the energy transfer mechanism Tb3+ >> Yb3+ will be discussed, referring to the mechanisms that have been proposed in the literature. In relation to the latter topic, the power dependence spectra for the luminescence of Yb3+: 2F5/2 >> 2F7/2 will be discussed.