Reciprocal and Non-reciprocal Chiroptical Features in Thin Films of Organic Dyes

The study of chiroptical properties in thin films of chiral organic pi-conjugated dyes is more complex than isotropic solutions, due to the interference of macroscopic anisotropies often present in the solid state. The experimental circularly polarized (CP) absorption (electronic circular dichroism, ECD) and CP emission (circularly polarized luminescence, CPL) of a thin film can be expressed as the sum of several terms, some of which are non-reciprocal upon film flipping. In this review, we shall discuss the fundamental theoretical concepts about reciprocal and non-reciprocal chiroptical features in thin films of organic dyes, describing their correlation with the solid-state structural organization and suggesting a practical toolbox to quantify their relative weight on an experimental ECD or CPL spectrum. Moreover, we shall also take into account the literature on thin films of organic pi-conjugated dyes showing strong non-reciprocal CP absorption and/or CP emission, due to their potential high interest in the flourishing field of chiral photonics and electronics.