Charge transport in low-band gap polymers studied with the CELIV technique

Abstract: Charge transport is one of the most important properties in both organic and inorganic opto-electronic devices. Few experimental methods are typically used to measure this parameter in organic materials field, such as Time of flight method (TOF) and the recently proposed charge extraction in linear increase voltage (CELIV). In this project, we aim to design the experimental setup for the CELIV method in the laboratory at ITN. The thesis starts with simple definition for the conjugated polymers and materials used and then describe the theoretical part of the method to be able to extract some important parameters such as sample thickness, mobility, conductivity and electric field. The estimation of the thickness of the sample is compared with other well-established techniques as X-ray diffraction (XRD), Atomic force microscope (AFM), Ellipsometery and DekTak. Measured values of mobility and conductivity are compared to TOF results. We vary different parameters, such as polymer solution concentration, input bias, delay time, temperature and electric field. Poly (3-hexyl thiophene) or P3HT and Poly (Para-Phenylenevinylene) or PPV are the polymers characterized in this project because they have different chemical properties (side group) and physical one (regularity of the chain) and they are well-studied materials via other techniques.