We discuss a set up for the Boltzmann - Poisson system for full electronic bands with a variety of boundary condition, including the effect of roughness. We present a a detailed numerical by means of DG schemes study of specular vs diffusive reflection conditions for a two dimensional domain with transport in full phase $k$-space (work in collaboration with Jose Morales Escalante-UT Austin and TU Wien). In addition, we also discuss a numerical implementation for a model of reactive interfaces in photoelectrochemical (PEC) solar cells, consisting in a hybrid domain decomposition model of a coupled Semiconductor/Electrolyte system implemented by LDG schemes through a Schwarz iteration for a electron/hole with couple to a red/ox coupled through a reactive interface (work in collaboration with Michael Harmon-UT Austin and JPMorgan Chase &Co, NYC, and Kui Ren (UT Austin)).