Transparent Ho3+/Tm3+/Er3+/Yb3 codoped Nano-Glass-Ceramics for Upconversion Head-Up Display
The commonly used automotive head-up display (HUD) technology is confronted with the problems of poor stability in organic resin counterpart and the unsatisfactory display effect of projection lighting source. To solve these issues, developing state-of-the-art materials and designing new HUD schemes with wide color gamut are of necessity. Herein, a series of pure red/green/blue (R/G/B) upconverting (UC) nano-glass-ceramics (GCs) containing lanthanide-doped NaLuF4 nanocrystals (NCs) are synthesized in a cost-effective, environment-friendly, and scalable manner, simultaneously achieving high crystallinity (~45.44 %) and high transparency (>80 %). Yb3+ was chosen as the sensitizer to Tm3+ (blue UC)/Ho3+ (green UC), due to its large absorption cross section from ground state 2F7/2 to excited state 2F5/2; meanwhile Er3+, Tm3+ co-doped into NCs can obtain pure red UC emission via promoting the population of Er3+ red-emitting 4F9/2 state. Consequently, the as-prepared materials exhibit high R/G/B color purity of > 80 % owing to the energy transfer between different lanthanide ions (Yb3+, Tm3+, Ho3+ and Er3+) upon 980 nm near-infrared (NIR) laser excitation, and possess superior thermal reversibility/water resistivity. Remarkably, two unprecedented HUD prototypes were constructed to demonstrate the application feasibility of developed pure R/G/B UC GCs.