Unique insights are gained with advanced optical spectrscopy into the working mechanisms of semiconductor materials for optoelectronics, which are crucial to advance device efficiencies. Scientifically, the connection between material structure and electronic properties is a fundamental question, for which mainly the limits of ordered (crystalline) and disordered (amorphous) semiconductors have been studied. Recently, the class of metal-halide perovskites have emerged as an intermediate semiconductor type, in which the soft-crystalline material structure leads to unexpected excited state dynamics, and for which the underlying physics remain unexplored. Unusually strong spin-orbit coupling was predicted to introduce Rashba-type state splitting in the electronic band structure of these materials, which is expected to affect recombination dynamics and spin-populations. It remains an open question, how dynamic changes in the material structure and electronic state populations, in combination with Rashba effects, control application-relevant electronic state nature and relaxation. In my talk I will present how we use advanced optical spectroscopy to study the dynamics of optically-excited electronic state populations, crystal structure and spin in functional hybrid perovskite semiconductors on ultrafast timescales. I will present results on layered and bulk metal-halide perovskites of varying dimensionality, for which I will discuss how the crystal structure and composition controls the properties and recombination of electronic states, and how these can enable highly-efficient optoelectronic devices and novel functionality.