Manifestation of chirality induced spin selectivity in chiral-photodiodes

We studied two enantiomers of chiral blends consisting of fullerenes (PC₇₁BM), chiral molecules (aza[6]H) and -conjugated donor-acceptor copolymers (F8BT), which exhibit significant circular dichroism (CD). These were examined using optical and optoelectronic methods in films and chiral photodiodes, where the chiral blend serves as the active layer. These techniques include chiroptical response, steady state photocurrent (PC) spectroscopy and time-of-flight transient PC. We found that the PC in the chiral photodiode is sensitive to the impinging light helicity and the chiral blend handedness, showing large dissymmetry with g_PC-factor ~20%. We show that the PC dissymmetry is caused by the chirality induced spin selectivity (CISS) in the active layer, where it serves as spin filter in the processes of the photogeneration and subsequent recombination across the polymer/fullerene interface, rather than the dissymmetry of the circularly polarized light absorption in the device, or the spin aligned carrier mobility. In particular, we demonstrate that the device PC dissymmetry spectrum does not follow the circular dichroism spectrum of the chiral blend and is sensitive to an applied magnetic field (i.e. Hanle effect). The CISS process is best manifested in the measured dissymmetry of the photocarriers lifetime under circular polarized light and by the Hanle effect.