Tunable photoluminescence and energy transfer of Eu3+,Ho3+-doped Ca0.05Y1.93-xO2 nanophosphors for warm white LEDs applications
Arpita Dwivedi, Monika Srivastava, Amit Srivastava, Chandan Upadhyay, Sanjay Srivastava
Abstract
Abstract A series of Eu 3+ ions doped Ca 0.05 Y 1.93- xO 3 :0.02Ho 3+ (CYO:Ho 3+ ,xEu 3+ ) nanophosphors having multicolour tuneability have been synthesised by following a simplistic solution combustion approach. The synthesised samples have been characterised by employing X-ray diffraction (XRD), Transmission electron microscope (TEM), and Fourier transforms infrared spectroscopy (FTIR). The optical properties have been engrossed by UV–visible and photoluminescent excitation and emission spectra, and decay lifetimes measurements. The characteristic emission, which occurs due to the f-f transition of Ho 3+ and Eu 3+ has been observed in emission spectra with excitation of 448 nm. By adjusting the doping ratio of Ho 3+ /Eu 3+ , the as-synthesized nanophosphor accomplishes multicolour tunability from green-yellow to red. Emission spectra and decay lifetime curve recommend dipole–dipole interaction causes energy transfer from Ho 3+ → Eu 3+ . The energy transfer process from Ho 3+ to Eu 3+ has been confirmed through electric dipole–dipole interaction with critical distance 15.146 Å. Moreover, temperature dependent emission spectra show the high thermal stability with an activation energy ⁓ 0.21 eV, with the quantum efficiency of 83.6%. CIE coordinate illustrates that the singly doped Ho 3+ and Eu 3+ lie in the green and red region, respectively, while the as-synthesized CYO:Ho 3+ ,xEu 3+ shows tunability from green to red with low CCT and high colour purity values. Hence, the CYO:Ho 3+ ,xEu 3+ nanophosphor may be a near-UV excited multicolour colour-tunable pertinent candidate with potential prospects for multicolour- display and near-ultraviolet lighting applications.