An increase in kVp increases the :
Increasing the kVp of an x-ray machine increases:

The number of photons generated.
The mean energy of the photons.
The maximal energy of the photons.

Ref:Ref: Oral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 10
Number of photons generated
Their mean energy
Their maximal energy
All of the above