• complex systems
• excitation energy transfer
• light-harvesting systems
• optical electronic spectroscopy
• photosynthesis
• spectral density

This work deals with the exploration of strategies for simulating lineshapes of optical spectroscopies of photosynthetic pigments and complexes. The first part of the thesis shows the effectiveness of a single tool, the spectral density, for reproducing high-resolution vibronic structure of single pigments. This tool can be applied to the simulation of both linear and nonlinear spectroscopies, such as absorption, fluorescence, Resonance Raman and two-dimensional optical spectroscopies. The second part of the thesis extends this formalism to multichromophoric systems. Exciton mixing, spectral densities of chromophores, the use of multiscale modelling and the inclusion of disorder effects, together with a suitable level of open quantum systems theory, are successfully applied to the study of optical spectra and energy transfer dynamics of a selected light-harvesting complex-Peridinin Chlorophyll Protein.