  This work establishes the relaxation limit from a bipolar Euler-Poisson
system with friction towards a bipolar drift-diffusion system. A weak-strong
formalism is developed and, within this framework, a dissipative weak solution
of the bipolar Euler-Poisson system converges in the high-friction regime to a
conservative, bounded away from vacuum, strong solution of the bipolar
drift-diffusion system. This limiting process is based on a relative entropy
identity for the bipolar fluid system.
