Highly Efficient and Tunable Filtering of Electrons' Spin by Supramolecular Chirality of Nanofiber‐Based Materials

Organic semiconductors and organic–inorganic hybrids are promising materials for spintronic‐based memory devices. Recently, an alternative route to organic spintronic based on chiral‐induced spin selectivity (CISS) is suggested. In the CISS effect, the chirality of the molecular system itself acts as a spin filter, thus avoiding the use of magnets for spin injection. Here, spin filtering in excess of 85% in helical π‐conjugated materials based on supramolecular nanofibers at room temperature is reported. The high spin‐filtering efficiency can even be observed in nanofibers assembled from mixtures of chiral and achiral molecules through chiral amplification effect. Furthermore and most excitingly, it is shown that both “up” and “down” orientations of filtered spins can be obtained in a single enantiopure system via the temperature‐dependent helicity (P and M) inversion of supramolecular nanofibers. The findings showcase that materials based on helical noncovalently assembled systems are modular platforms with an emerging structure–property relationship for spintronic applications. Helical supramolecular nanofibers of π‐conjugated molecules exhibit high spin‐filtering efficiency at room temperature. The magnitude of spin filtering is controlled through chiral amplification. Interestingly, the orientation of the spins transferred through the nanofibers is modulated by temperature‐dependent helicity switching of nanofibers. Thus, a molecular design is presented for complete control over both the efficiency and the polarity of spin filtering.