This course offers an introduction to electronic processes in conjugated organic materials nowadays used in many different optoelectronic devices such as lightemitting diodes and organic solar cells. The theoretical basics of electronic transitions and excited states (excitons) are discussed first, followed by an overview of basic measurement (spectroscopy) techniques. Furthermore, emission spectra of single molecules,ensembles, and aggregates are reviewed and basic concepts of energy transfer and photoexcitations in conjugated polymers are introduced. Finally, the course offers an overview of technological applications of semiconducting organic materials and an introduction to advanced (time-resolved) spectroscopy and data analysis techniques.