  We present a theoretical account of some of the most likely hydrogen-related
reactions with impurities in n-type and p-type solar-grade silicon. These
include reactions with dopants and carbon, which are relevant in the context of
life-time degradation of silicon solar cells, most notably of light and
elevated temperature degradation (LeTID) of the cells. Among the problems
addressed, we highlight a comparative study of acceptor-enhanced dissociation
of hydrogen molecules in B- and Ga-doped material, their subsequent reaction
steps toward formation of acceptor-hydrogen pairs, the proposal of mechanisms
which explain the observed kinetics of photo-/carrier-induced dissociation of
PH and CH pairs in n-type Si, analysis of reactions involving direct
interactions between molecules with P and C, and the assignment of several
electron and hole traps with detailed atomistic- and wavefunction-resolved
models.
