Introduction Laser-driven white lighting has received much attention due to its high brightness, high efficiency, and compact size. Blue laser active inorganic color converter technology is a commonly used method to produce white laser lighting due to its cost-effectiveness and simple structure. However, the existing laser lighting endures a low color rendering index (CRI) because of insufficient cyan-green and red light components in the spectra of existing color converters. Therefore, there is a demand for the development of color converters with intense cyan-green and red emission to improve the optical performance of laser lighting.Methods (Ca0.98-xNaxCe0.02)3Sc2Si3O12 (x=0, 0.02, 0.04, 0.06, 0.08) (CSS) phosphors were synthesized by a solid-state reaction method. The prepared CSS phosphors were then blended with commercial CaAlSiN3: Eu2+ (CASN) phosphors at different weigh ratios (abbreviated as R/G), which were chosen to be 1/8, 1/12 and 1/20. An inorganic binder used was commercially available silica colloidal particles, while an organic binder was polyvinyl pyrrolidone (PVP). Firstly, phosphors, PVP and silica colloidal particles were prepared by thoroughly mixing at a mass ratio of 150:50:1. The resulting slurries were coated on the sapphire substrates via blade coating. Finally, the dried samples were sintered in a muffle furnace at 600 ℃ for 20 min to remove the organic residues.Results and discussion The CSS host has a cubic Garnet-type structure with the Iaˉ3d space group. Na+ ions are introduced into the CSS host to function as a charge compensator. This enables the elimination of the impurity phases of phosphors. Under the excitation of blue light at 450 nm, the CSS phosphors emit a broadband cyan-green light with a peak at 507 nm. As Na+ content increases, the emission intensity of CSS phosphors gradually increases due to the enhanced absorption efficiency (AE) and internal quantum efficiency (IQE). As x = 0.06, the emission intensity reaches its maximum, which is corresponding to internal/ external quantum efficiencies (IQE/EQE) of 86% and 55%, respectively.Dense CSS films were produced using colloidal silica. Clearly, the film is composed of tightly packed phosphors and the gaps between phosphor particles are also filled with SiO2. The film is bonded to the substrate tightly, which can be ascribed to the adhesion function of the colloidal SiO2. The surface of the film is sufficiently smooth without polishing, and its thickness is 135 μm. The SiO2 colloidal particles serve as an effective inorganic binder, a filler of gaps and a protective coating.The excitation and emission spectra, decay curves and quantum efficiency of the CSS film are similar to those of the related CSS phosphors. The unimpaired luminescence properties of the film indicate that sintering does not impair the intactness of CSS phosphors. The CSS film displays a thermal quenching at evaluated temperature, and the decrease of the integrated emission intensity of CSS film aligns with that of CSS phosphors, retaining 86% of its initial value at 200 ℃. When the incident laser power increases from 0.3 W to 5.30 W, the emission intensity of the film increases monotonously. However, when the laser power further increases to 6.20 W, the emission intensity of the film decreases sharply and a luminous saturation appears. The maximum luminous flux of 717?lm is achieved at an incident laser power of 5.30 W, and the corresponding luminous efficacy is 135 lm/W.Although the CSS film exhibits a high thermal stability and a high luminous efficacy, the CRI of this phosphor-converted white light is 57 due to the deficiency of red light components. To improve the CRI, a composite film comprising CASN and CSS phosphors was fabricated. When the mass ratio of CSS and CASN phosphors is 1/12, the spectral analysis of the composite film reveals a uniform distribution of cyan-green, yellow and red light components, with a half-height width of 176 nm. Also, when excited by 5.3 W blue laser, the composite film emits a white light with a high luminous flux of 647 lm, a luminous efficacy of 122?lm/W and a CRI of 88.Conclusions Highly efficient cyan-green CSS phosphors with an IQE/EQE of up to 86%/55% were prepared via introducing charge compensatory additives Na+. A composite phosphor film was developed on thermally conductive sapphire substrates using silica colloidal particles as an inorganic binder via combining the prepared cyan-green CSS and commercial red CaAlSiN3:Eu2+ phosphors. The phosphor film exhibited a superior thermal stability and it maintained 84% of its room-temperature luminescence intensity even at 200 ℃. The spectral analysis of the film showed an even distribution of cyan-green, yellow and red light components, with a half-height width of 176 nm. Under 5.3 W blue laser excitation, the composite film emitted a white light with a high luminous flux of 647 lm, a luminous efficacy of 122 lm/W and a CRI of 88. These results indicated that the composite phosphor film could have a promising potential for application in high-brightness laser lighting with superior color rendering.