Upconversion luminescence, intensity saturation effect, and thermal effect in Gd2O3:Er3,Yb3+ nanowires

Abstract

In this paper, the upconversion luminescent properties of Gd2O3:Er3+,Yb3+ nanowires as a function of Yb concentration and excitation power were studied under 978-nm excitation. The results indicated that the relative intensity of the red emission (4F(9/2)-4I(15/2)) increased with increasing the Yb3+ concentration, while that of the green emission (4S(3/2)/2H(11/2)-4I(15/2)) decreased. As a function of excitation power in ln-ln plot, the green emission of 4S(3/2)-4I(15/2) yielded a slope of approximately 2, while the red emission of 4F(9/2)-4I(15/2) yielded a slope of approximately 1. Moreover, the slope decreased with increasing the Yb3+ concentration. This was well explained by the expanded theory of competition between linear decay and upconversion processes for the depletion of the intermediate excited states. As the excitation power density was high enough, the emission intensity of upconversion decreased due to thermal quenching. The thermal effect caused by the exposure of the 978-nm laser was studied according to the intensity ratio of 2H(11/2)-4I(15/2) to 4S(3/2)-4I(15/2). The practical sample temperature at the exposed spot as a function of excitation power and Yb3+ concentration was deduced. The result indicated that at the irradiated spot (0.5 x 0.5 mm2) the practical temperature considerably increased.

Synthesis and upconversion luminescence properties of monodisperse Y2O3:Yb, Ho spherical particles

“…This can be further demonstrated by the slope values of the ln-ln plot of the green emission intensity as a function of excitation power. Based on the reports by Pollnau et al [26] and Song et al [27,28] Fig. 5(c)).…”

Upconversion and colour tunability of Gd2O3:Er3+ phosphor prepared by combustion synthesis method

“…When graph is plotted between 'log I' and 'log P' for different emission bands it shows linear relation between them with the slope 'n'. Value of 'n' represents the number of photons participating to populate the emitting stark levels [30,31]. The value of 'n' for red emission band at 667 nm, green emission bands at 553 nm and 568 nm, and blue emission band at 409 were 1.67, 1.56, 1.61 and 2.53 respectively (Fig 8).…”

Up-conversion luminescence of Er3+ doped and Er3+/Yb3+ co-doped YTaO4

“…For the Er 3+ /Yb 3+ co-doped system, according to Lei et al [17] , if two-step energy transfer is the dominant mechanism, then as Yb 3+ concentration increases, the dependence of up-conversion emissive intensity on pumping power will vary from quadratic to liner, namely the slope will decrease in the range of 1-2. However, Figure 4 shows an inconsistent result.…”