Magnetoresistance In Organic Semiconductor

Organic Magnetoresistance (OMAR) has drawn researchers1 attention all around the world because of its great theoretical and practical value. So far, although there are many theoretical models attempting to explain OMAR, the models have their own limits. Most agree that magnetic field affects particles and quasiparticles through hyperfine interaction field, but how the current changes is still controversial.In previous studies, people try to use different types of materials and device structures to study the mechanism of OMAR, but the difference caused by materials and structures makes it difficult to study it accurately. We use new systems to control the variables so we can get better result.At the beginning, we have done a lot of work on the experimental method. After comparing different methods, we finally found the right experimental method for our system.We studied systematically on the OMAR of P3HT, which is a common material By studying the relationship between OMAR and the intensity of the magnetic field, the current/voltage, temperature, electrode material and other factors, we think there are two independent components contribute to the OMAR. One is MR+, which can be explained by bipolaron theory, the other is MR-, which can be explained by electron-hole theory.On this basis, we studied the effect of the polymer chain-length on OMAR. We found that the MR+ component was irrelevant to the interchain interaction, while the MR-was affected by the interchain interaction.Furthermore, we studied study the influence of the physical device on OMAR by using ferroelectric-polymer system so we can eliminate effect of device and electric field. Preliminary research have shown that the presence of a sufficient amount of carriers is a prerequisite for generating OMAR effect.