Highly efficient NIR to visible upconversion in a ZnO:Er,Yb thin film deposited by a AACVD atmospheric pressure process

Abstract

ZnO:Er³⁺,Yb³⁺ thin films with a hexagonal wurtzite structure were successfully deposited on Si (111) substrates at 430 °C by an aerosol-assisted chemical vapor deposition (AACVD) atmospheric pressure process. The films were deposited with fixed 3 mol% erbium concentration and various ytterbium concentrations of 6, 8, 9 and 10 mol%. The annealing treatment at 1000 °C was found to enhance the crystallinity and the upconversion (UC) emission of the films. UC emissions were investigated under 980 nm excitation, and the ZnO:Er³⁺,Yb³⁺ films exhibited the intense red 665 nm upconverted emissions of Er³⁺ ions originating from an efficient Yb–Er energy transfer process. The absolute upconversion Quantum Yield (UC-QY) of each film was measured for the UC emissions centered at 410, 540 and 665 nm at varying excitation power densities. UC-QY analysis has revealed that the ZnO:3 mol% Er,9 mol% Yb thin film possesses the highest total quantum yield of 5.59 ± 0.1% with a power density of 19.3 ± 3 W cm⁻². These results show that this film is promising as an efficient upconversion layer suitable for many photonic applications.