Tetracyanoanthracenediacenaphthalimides\nas n‑Type\nOrganic Semiconductors: Control of Molecular Orientation

We investigated tetracyanoanthracenediacenaphthalimides\n(TCDADIs)\nas n-type organic semiconductors (OSCs) and assessed their molecular\nself-assembly in forming monolayers and thin films using optical absorption\nspectroscopy, scanning tunneling microscopy (STM), atomic force microscopy\n(AFM), and grazing incidence wide-angle X-ray scattering (GIWAXS).\nThe absorption spectra, along with quantitative GIWAXS analysis, reveal\nthe influence of molecular structure (alkyl chain length) and film\nprocessing conditions (annealing temperature and spin-coating speed)\non the orientation of TCDADI molecules in films. Our findings indicate\nthat increasing the spin-coating speed and annealing temperatures\ncauses a transition from a mixed phase to a predominantly edge-on\nmolecular orientation. This transition significantly enhances the\nelectron mobility, from 0.01 to 0.05 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> for TCDADI-C16 and from 0.13 to 0.20 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> for TCDADI-C24.\nIn addition, we highlight the potential of TCDADIs for photodetector\napplications, showing a photoresponse gain of over 2000 under white\nlight.