We report the bi-polaron transport and magnetic field induced Pauli spin-blockade in solid-state molecular junctions (MJs) evidenced by a positive magnetoresistance (MR). The junction was made of thin layers of redox-active ruthenium polypyridyl-oligomers Ru(tpy)2 sandwiched between conducting amorphous carbon (a-C) electrodes. The redox-active Ru(tpy)2 molecule, which enables small polaron and deep traps in the charge transport of the Ru(tpy)2 MJ as revealed by the temperature-dependent current-voltage response, leads to the formation of the bi-polaron and magnetic field induced Pauli spin blockade, resulting into the MR. At the meantime, the reliable and controllable device performance renders a rigid thickness-dependent MR evolution. The bi-polaron transport revealed in our study underscores the importance of the multi-particle transport by molecular design in MJs and laid the foundation for magnetic-electronic function in molecular-scale devices.
Keywords: Electron Transport; Magnetic Properties; Molecular Devices; Molecular Electronics.
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