LAUSR

DOI: 10.1002/aelm.201900318 recombination in organic light-emitting diodes and organic magnetoresistance (MR) devices.[9–12] Moreover, organic semiconductors have obvious advantages, lower cost, and better flexibility, and they have greater possibility in wearable and large area applications.[13–20] The most common prototype organic device using spin freedom is organic spin valves (OSVs),[5,11,21–25] which consist of a nonmagnetic spacer sandwiched between two ferromagnetic (FM) electrodes, and based on the alignment of the electron spin relative to the FM layer magnetization orientation. In this research field, there are tunneling and diffusive regimes.[26] The tunneling regimes occur in relatively thinner spacers (<15 nm), and the mode is weakly dependent on temperature. The diffusive regimes are also called hoping in organic spintronics. This mode occurs in relatively thicker layers (≥15 nm), and it is strongly dependent on temperature. In addition, the present study lies in the diffusive regime owing of the conductivity mismatch problem and more abundant phenomena like Hanle effect in organic spintronics. For organic semiconductor, both spin–orbit interaction and the hyperfine interaction play very significant parts in determining the spin relaxation, but the origin of determining the spin relaxation in organic semiconductors is still unknown. Herein, OSV effect is characterized by the MR ratios, defined as MR = (Rap − Rp)/Rp, where Rap and Rp denote the resistance in the antiparallel and parallel states of FM electrode magnetization direction, respectively. There are lots of efforts to explore organic spintronics Organic materials are proposed to be excellent spin transport layers due to their weak hyperfine and spin–orbit coupling interaction. Donor−acceptortype polymers PTDCNTVT-420 and PTDCNTVT-320 with diketopyrrolopyrrole (DPP) units are employed as the spacers in the organic spin valves, which have more advantages such as solution processing, higher mobility, and large area fabrication. The performance of polymers spin valves based on DPP units with different alkyl side chain lengths are studied. The different top ferromagnetic (FM) electrodes Co and Ni80Fe20 are used for spin detection resulting in obvious distinct magnetoresistance (MR) values. The MR ratio of approaching 30% at 10 K is achieved with the Ni80Fe20 electrodes using PTDCNTVT-420 with longer alkyl side chain lengths. Moreover, the MR behaviors are observed depending on various temperatures, which are related with the FM electrodes spin injection efficiency. The direct spinterface are also investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). In addition, the series of results indicate that the PTDCNTVT polymers can be used as good spin transport model materials and give clues for future polymers spintronic studies.