Regulation of Bi3+ emission in Ca3Ga4O9 phosphors through doping concentration and solid-solution component design

Cyan phosphors that emit light in the 480–520 nm range are crucial to achieving high-quality full-spectrum lighting with superior color rendering index and color temperature. In this study, we employed doping concentration and solid-solution component design strategies to control the luminescence properties of Ca3Ga4O9 (CGO): Bi3+ phosphors. CGO crystallized in the orthorhombic crystal system with a Cmm2 (35) space group and exhibited a band gap energy of 4.56 eV. Optimal excitation at 345 nm resulted in CGO: xBi3+ with asymmetric emission spectra in the 370–650 nm range, with a peak at 490 nm. These spectra can be decomposed into two distinct peaks: the long-wave peak Bi(1) at 495 nm, resulting from the occupation of Ca(Ⅰ) (CaO6) by Bi3+, and a short-wave peak Bi(2) at 445 nm, resulting from the occupation of Ca(Ⅱ) (CaO8) by Bi3+. Furthermore, the introduction of Sr2+ ions led to enhanced emission from Bi(2) ions and reduced emission from Bi(1) ions, resulting in tunable luminescence. The decrease in decay lifetime indicated the migration of Bi3+ ions from the luminescence center Ca(Ⅰ) to Ca(ⅠⅠ). The quantum yield and activation energy of the CGO: 0.01Bi3+, 0.7Sr2+ phosphor were 28.82% and 0.3469 eV, respectively. Lastly, the color rendering index values of the LED devices based on CGO: 0.01Bi3+, 0.7Sr2+ were high (R5 = 96.9 and R12 = 90.0), indicating its potential as a broadband cyan phosphor for full-spectrum LED applications.