Enhanced NIR optical properties of a single-site-occupied ultra-broadband InNbTiO6:Cr3+ phosphor at 965 nm through Ga3+ doping

Abstract

Most near-infrared (NIR) phosphors suffer from short emission wavelength (<1000 nm) and narrow full width at half maximum (FWHM) values below 200 nm, restricting their broader applications in non-destructive tests, spectral analysis and photovoltaic fields. This study presents the successful synthesis of the wolframite-type compound InNbTiO₆:Cr³⁺, with Cr³⁺ occupying a single In³⁺ site. Under green light irradiation, it emits an ultra-broadband NIR spectrum centered at 965 nm with a FWHM of 231 nm. Substituting In³⁺ with Ga³⁺ induces a blue shift in the emission peak from 969 nm to 934 nm, concomitant with an enhancement in the optical properties. To be specific, the NIR luminescence intensity of In_0.58NbTiO₆:0.02Cr³⁺,0.4Ga³⁺ is enhanced by a factor of 2.3, and its thermal stability is improved from 22.3%@400 K to 41.3%@400 K compared to In_0.98NbTiO₆:0.02Cr³⁺. The NIR pc-LED is fabricated by integrating the In_0.58NbTiO₆:0.02Cr³⁺,0.4Ga³⁺ phosphor with a 520 nm chip, showcasing its potential for multifunctional applications in solar cells, spectral analysis, and night vision technologies.