PTCDI-Ph Molecular Layer Stack-Based Highly Crystalline Microneedles As Single-Component Efficient Photodetector

Phenyl-substituted perylene diimide derivative N,N-diphenyl perylene tetracarboxylic diimide (PTCDI-Ph) has been used as a single-component organic material to fabricate an efficient photodetector. PTCDI-Ph grows as one-dimensional microneedles composed of stacks of molecular layers with substrate temperatures. Such structure formation is due to the lower diffusion activation energy (0.21 eV) of the molecules along the length of the microneedles than along the width (0.34 eV). The photoresponse from these structures has been significantly enhanced because of the reduction of traps as a result of enhanced diffusion of the molecules at higher substrate temperatures. The observed photosensitivity and photoresponse time of the devices fabricated with the films grown at a 140 °C substrate temperature are 333 and 0.12 s, respectively. The decrement of the traps due to the defect states with the increment of substrate temperature is confirmed by the photoluminescence (PL) and time-resolved photoluminescence spectra (TRPL). The photocurrent covers the visible-light spectrum, indicating that the PTCDI-Ph microneedle is a promising candidate for the fabrication of single-material-based photodetectors.