Quantum dot (QD) color-converted mini/micro-LED displays are considered as the most promising technology for next-generation display with the benefits of high production yield, low cost and good process reproducibility. However, it is still facing the challenge of optical crosstalk among adjacent subpixels, which degrades the display resolution and worsens the color rendering. To reduce the optical crosstalk, this paper presents an effective structure to confine the blue backlight paths by a deep reactive ion etching (DRIE)-fabricated silicon light confining grid. By optical simulations, this paper validates the effectiveness of silicon light confining grid on optical crosstalk reduction, and the influence on pattern design of silicon light confining grid is also discussed. A prototype display based on designed structure is assembled and the reduced optical crosstalk effect is confirmed by a microscope. Both simulation and experiment results demonstrate the effectiveness of the crosstalk-reduced design.