Dear Brother Dihak, Hope you are well! I will give you a conceptual answer that is suitable for ant semicondcutor material. When photons of light with proper wavelength are absorbed by a semiconductor material, the absorbed photons boiled excitons. The excitons are bound electron hole pairs. Their binding energy depends basically on the dielectric consatnt of the semiconductor material. In order to calculate the binding energy one uses the hydrogen - like model where where one considers the exciton as a hydrogen atom but with dielectric consatnt instead of the one for the original hydrogen atom. Based on this model one can get the exciton energy. Practically as an example for silicon with epsilon = 11, The exciton energy is in the order of the thermal energy at room temperature and the excitons are dissociated to free electrons and holes. Contrary, for organic semiconductors with epsilon of about 4, the excitons are strongly bonus in the order or 0.3 eV. Therefore they need a dissociation technique for getting electron and holes. This is practically accomplished by using the so-called acceptor materials. The perovskites are materials having high dielectric constant and they behave as silicon. As the molecules gets larger the dielectric consatnt increases. But the issue is the dielectric constant itself as I explained. For more information you may refer to the paper: https://www.researchgate.net/publication/332241539_Generic_Analytical_Models_for_Organic_and_Perovskite_Solar_Cells Best wishes

• 📷View full-textSourceConference Paper: Generic Analytical Models for Organic and Perovskite Solar Cells Abdelhalim abdelnaby Zekry · Imene Yahyaoui · Fernando TadeoFull-text available · Conference Paper · Mar 20