An Exposure is all about light and sensor sensitivity! Ways to get a brighter exposure are to either get a slower shutter speed ( which you obviously dont want ), get a faster aperture ( which you could do by purchasing a faster lens ), or turn up your ISO.
However, all of these have drawbacks potentially.
Slower shutter speed = more light but may blur motion
Faster aperture = more light but shallower DOF and may cause things to be OOF
Higher ISO = brighter exposure but adds noise to the picture
Pick your poison!