In this work, time-resolved luminescence on thin-film semiconductors is studied by meansof analytical and numerical mathematical methods. The calculations are based on the continuityequations, the current equations as well as the Poisson equation. These are solvedboth numerically using the simulation tool Synopsys®TCAD and approximate analytically. In course of there, the effect of band-to-band and Shockley-Read-Hall-recombinationin the bulk and at the surfaces, as well as the impact of drift and diffusion of charge carrierson the time-dependent decay of the luminescence are investigated. The results show that for single absorber layers under low injections, an exponential time-dependent decay of the luminescence is expected.