Circularly polarized light (CPL) has diverse applications in a myriad of fields. Crucial to CPL technologies is the ability to discern between left- and right-handed CPL through CPL-sensitive photodetectors. Here, we studied chiral photodetectors based on two enantiomers of chiral bulk heterojunctions (BHJ) consisting of fullerenes (${\mathrm{PC}}_{71}\mathrm{BM}$), chiral helicene molecules ($\mathrm{aza}[6]\mathrm{H}$), and π-conjugated donor-acceptor copolymers (F8BT), which exhibit significant circular dichroism (CD). We found that the photocurrent (PC) in the chiral photodiode is sensitive to the impinging light helicity and the chiral BHJ handedness, showing a large dissymmetry $g_{\mathrm{PC}}$-factor of ∼20%. Using optical and optoelectronic methods, we demonstrate that the device PC dissymmetry spectrum does not follow the CD spectrum of the chiral BHJ, which contrasts with other CPL photodetectors that rely on large CD, and is sensitive to an applied magnetic field. The methods include chiroptical response, steady-state PC spectroscopy, and time-of-flight transient PC. We show that the PC dissymmetry is caused by the chirality-induced spin selectivity (CISS) in the active layer, where it serves as a spin filter in the photogeneration and subsequent recombination processes across the polymer/fullerene interface, rather than the circularly polarized light absorption in the device or the spin-aligned carrier mobility. The CISS process is best manifested in the measured dissymmetry of the photocarrier’s lifetime under circularly polarized light that is influenced by a magnetic field. Our experiments could be used to prove the existence of CISS in other chiral materials, where the chiral chromophores are randomly oriented.

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• Chirality
• Photocurrent
• Spin optoelectronics
• Organic semiconductors
• Photodiodes