Study On Organic Optoelectric Materials By Transient Photovoltage Technique And Magnetic Modulation Study

Due to the promising future of small-weight molecular organic solar cells, much attention has been paid in this research field over the past two decades. Although steady progress in the performance of organic photovoltaic cells has been achieved, the power conversion efficiency and the lifetime of an OPV cell is still not applicant for manufacturing. Without the clear grasp of basic mechanisms in physical processes of OPVs, lots of problems are still unsolved, which is crucial to the improvement of OPVs.Our research is based on the excitonic process of small-weight molecular organic solar cells. We mainly worked on two aspects, the transient photovoltage study and magnetic field effect of OPVs.We applied the transient photovoltage technique to investigate the interfacial dissociation properties at ITO/Pentacene interface. At room temperature, it was found that no interfacial dissociation could be observed, even changing the direction of built-in field or the thickness of Pentacene. Moreover, PL intensities of thin-film pentacene increase with decreasing temperature, which is similar to inorganics rather than organic ones. According to former results, the lowest-lying excitons of pentacne cannot be frenkel excitons and should be some excitons with larger diameters. Thus, we could get the conculsion that excitons in pentacene tend to separate into free carriers at room temperature, which leads to the result of no interfacial dissociation signal in transient photovoltage results.On the magnetic field effect, an increase of Isc of 2.5% is observed at the magnetic field of 1500Oe while the dark current has no change. This means that the photocurrent can be changed by magnetic field. The photocurrent increases with increasing magnetic field.Besides, a matlab software was programmed to stimulate organic solar cell. It's based on genetic algorithm. This small software is very useful for guidance of experiment.