ABSTRACT
It has been found the influence of magnetic nanoparticles (Ni, Cu-Ni alloy, Fe in carbon nanotubes (Fe-CNT), Fe3O4) stabilized by polyalkanetherimide
(PAEI) on photoelectric sensitivity (PES), carrier photogeneration quantum yield β and the residual potential of composite films based on soluble photoconductive polyimides (PI) with PAEI, and also on p – and n – transport layers of photovoltaic cells based on polymer p-n heterostructures. It has been shown that the magnitude and sign of the effect is determined by the structure of PI, type of charge transfer interaction (interchain or intrachain) and also by the degree of surface coating of MNP with adsorbed PAEI macromolecules. At zero and low coverage (N < 50 macromolecules per MNP) the changing of positive effect to negative is observed. For N=100-200 there is the maximum positive effect (growth of PES by 4.7-5.0 times and the photogeneration quantum yield by 1.6-2.5 times), and for N > 200 effect decreases. It is suggested that the effect is connected with the redistribution of PAEI in the volume caused by effective adsorption of PAEI macromolecules on the surface of MNP. This redistribution significantly affects PES, the magnitude of β and carrier drift length lD both because of the interchain nature of EDA interaction in PI and because of the strong (exponential) dependences of these values on the distance between transport centers for carrier hopping conductivity and photogeneration mechanisms. Alternative explanations (magnetic-spin effects in the field of MNP, the scattering of light by particles) is also considered. The magnitude of the magnetic field of Ni-Cu MNP has been estimated using studied earlier low field magnetic effect on the luminescence of PAEI composites with rubrene. Although the chaotic orientation fields of individual particles the magnetic spin effect from MNP, depending on square of local field strength, is not zero. Measurements showed that the luminescence intensity change in the MNP field (–3%) corresponds to a magnetic effect in homogeneous external field with the strength H0 > 10 Oe. This value has been taken for the effective average MNP field strength within the composite film at particles content of 6 mass.%.
