Do standard white LEDs produce a full spectrum of light?
@Shamtam have already commented that:
(1) the light from a typical while LED doesn't match the spectrum of the sunlight
(2) white LEDs are blue LEDs with additional phosphor  

This is to expand on @Shamtam's comment.

 
Spectrum of a white LED showing blue light directly emitted by the GaN-based LED (peak at about 465 nm) and the more broadband emitted by the phosphor.
(source: Wikipedia)


Diagram of the spectrum a LED lamp (blue), a CFL (green) and an Incandescent (purple) superimposed the solar spectrum (yellow). Note that the energy used by each lamp is at least the area underneath its curve.
(source)