The present invention provides a novel substance having an excellent color purity of blue, a light-emitting element and a light-emitting device using the novel substance. The multi-speed transmission assembly outputs rotary power to a differential assembly. The housing includes a bottom wall, a sidewall extending upwardly from the bottom wall and a bracket for supporting the impeller thereon. The output driver also includes a number of series capacitors, each associated with one of the driver segments. In an axial direction of the rotor, the retaining plate extends to be above and within a rotational area of the blades to retain the rotor to avoid departure of the rotor from the housing, even if the heat-dissipating fan is hit hard while it is packed, moved, transported or operating.