Semi-transparent, Chiral Organic Photodiodes with Incident Direction-dependent Selectivity for Circularly Polarized Light.

Detection of the circular polarization of light is possible using chiral semiconductors, yet the mechanisms remain poorly understood. Semitransparent chiral photodiodes allow for a simple experiment to investigate the basis of their selectivity: changing the side from which the diode is illuminated. We observe a reversal of circular selectivity in photocurrent generation when changing the direction of illumination on organic, bulk-heterojunction cells. The change in selectivity can be explained by a space charge limitation on the collection of photocarriers in combination with preferential absorption of one of the circular polarizations of near-infrared light by the chiral non-fullerene acceptor. The space charge limitation is supported by detailed measurements of frequency and intensity dependence of dc and ac photocurrents. This article is protected by copyright. All rights reserved.