The effect of annealing temperature on the luminescence properties of Y₂O₃ phosphor powders doped with a high concentration of Bi³⁺

The effect of different annealing temperatures on the photoluminescent properties of bismuth doped yttrium oxide (Y_2−xO₃:Bi_x)phosphor powders was investigated with various optical spectroscopy instruments for a possible down-conversion candidate for solar cells. Results showed that the emission intensity increased by increasing the annealing temperature to 1400 °C.Time of flight secondary ion mass spectroscopy and X-ray photoelectron spectroscopy were used to characterize the surface of the samples after annealing. The intensity increase up to 1200 °C was due to the segregation of Bi³⁺ ions from the bulk to populate the particles' surfaces as a result of tthe Bi³⁺ionГ—Віs concentration on the sampleГ—Віs surface. The decrease in the dopant concentration then resulted in a lesser effect from concentration quenching. Further increase in the annealing temperature to 1600 °C resulted in a decrease in the intensity because the majority of the Bi³⁺ ions evaporated as volatile species, from the sampleГ—Віs surface.