The combination of mixed quantum-classical dynamics with efficient electronic structure methods was developed in order to simulate light-induced processes in complex molecules, multichromophoric aggregates and metallic nanostructures. We will first demonstrate how the combination of real-time simulations with experimental pump-probe techniques such as time-resolved photoelectron imaging (TRPEI) allows to fully resolve the mechanism of excited state relaxation through conical intersections in prototype organic molecules. Currently, there is growing evidence that nonadiabatic relaxation processes also play a fundamental role in determining the efficiency of excitonic transfer or charge injection in materials for energy conversion. Since such systems are currently out of the reach of the state-of-the-art quantum chemistry a development of even more efficient quantum chemical approaches is necessary in order to describe the excited state dynamics in such assemblies. For this purpose we have recently introduced long-range corrected timedependent density functional tight binding (LC-TDDFTB) method and have combined it with our field-induced surface hopping dynamics (FISH). The methodology has been applied to the simulations of energy transfer dynamics and exciton relaxation in several classes of materials including organic crystals, self-organized dye-foldamers and donoracceptor systems leading to a molecular level insight into the energy conversion processes. As an outlook, we will present recently introduced multistate metadynamics methodology, which allows for fully automatic sampling of conical intersections seams in complex systems, thus providing fundamental information about their nonradiative decay channels.