We employ time resolved and non linear spectroscopy to get an insight into the excited state mechanism of light to energy conversion processes in organic materials. The investigated organic compounds are new potential active materials for photons-to-current conversion in Organic Photovoltaics (electron donors or acceptors; singlet fission materials) or for current-to-photons conversion in Organic Light Emitting Diodes (fluorophores showing Aggregation Induced Emission, Room Temperature Phosphorescence and Thermally Activated Delayed Fluorescence).