The Nanosprouts Structural Inhomogeneity of Organic Semiconductors and the Optical Memory Properties

Abstract

Structural inhomogeneities are extensively observed in organic films. Detailed understanding of the crystal lattice packing modes and orientations of these inhomogeneity structures will provide insightful views in revealing the relationship between film morphology and device performance. Herein, this study reports a characterization approach utilizing the lateral force microscopy (LFM) to directly obtain lattice structure information on a commonly used organic small molecular material, i.e., 2,9-Diphenyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes (DPh-DNTT) deposited by thermal evaporation. By enhancing sensitivity, the spatial resolution of the LFM approach is optimized. The crystal structure information up to sub-molecular scale can be resolved through the optimization of the LFM test, enabling precise determination of molecular arrangements. Based on the nanosprouts structural inhomogeneity, DPh-DNTT nonvolatile optical memory transistors (OMTs) are developed and the devices demonstrate intrinsic optical memory property with a long retention time of over 1 × 10⁴ s, accompanied by a binary state current ratio greater than 10⁵. Besides proposing the utilization of Kelvin probe force microscope (KPFM) and LFM to identify the charge trapping sites of the OMT, a 16 × 16 flexible active matrix OMT array is fabricated with image processing capability. The devices showcase their potential for applications in the field of machine vision.