This book is focused on the application of temperature dependent photo- and electroreflectance spectroscopy in order to study novel and potential materials in solar energy conversion. Photoreflectance and electroreflectance belong to the modulation spectroscopy techniques, where during reflectance measurements, the external modulation is applied in respect to one system parameter. Within the techniques used in this work, the periodically modulated parameter was the built-in surface/internal electric field. Changes in the electric field cause changes in the complex dielectric function and this...