Octupole Moment Driven Free Charge Generation in Partially Chlorinated Subphthalocyanine for Planar Heterojunction Organic Photodetectors

Abstract In this study, high-performance organic photodetectors (OPDs) are presented which utilize a pristine chlorinated subphthalocyanine (Cl6-SubPc) photoactive layer. Optical and optoelectronic analyses indicate that the device photocurrent is primarily generated through direct charge generation within the Cl6-SubPc layer, rather than exciton separation at layer interfaces. Molecular modelling suggests that this direct charge generation is facilitated by Cl6-SubPc’s high octupole moment (-80 DÅ2), which generates a 200 meV shift in molecular energetics. Increasing the thickness of Cl6-SubPc leads to faster OPD response times, correlated with a decrease in trap density. Notably, PHJ OPDs with a 50 nm thick Cl6-SubPc photoactive layer exhibit detectivities approaching 1013 Jones, with a dark current below 10− 7 A cm− 2 up to -5 V. Based on these findings, we conclude that Cl6-SubPc is a promising material for high-performance OPDs employing a single-component photoactive layer.