electronic components. Feynman [1] first proposed the concept of "molecular electronics" in 1959 at the annual meeting of the American Physical Society. The formal birth of molecular electronics was marked by Aviram and Ratner's theoretical prediction of the rectifier properties of the donor-bridge-receptor system of organic molecules. [2] Due to technical limitations, the research of molecular electronics has been a semi-empirical theoretical calculation for quite a long time. [3] The breakthrough in molecular electronics was the development of the scanning probe microscope (SPM), [4] which enables the visual analysis of the surface morphology of the sample. With the update of research methods and techniques, Reed achieved conductivity measurement of the single Benzene-1,4-dithiol (BDT) molecule junction by mechanically controllable break junction (MCBJ). [5] This is the first experimental work in molecular electronics. Xu [6] reported the repeated measurement of single molecule resistance using scanning tunneling microscope (STM) and developed a set of statistical methods for the research of single molecule electron transport. Since then, the preparation of molecular junctions and the measurement of electrical properties have been greatly developed. [6,7] The multilayer edge molecular electronics device (MEMED) approach [8] can better connect the tunnel junctions with the metal electrodes to achieve higher control accuracy. Such as SPM, MCBJ, electromigration nanogap, [9] electrochemical deposition, [10] surfacediffusion-mediated deposition, [11] nanoimprint lithography, [12] nanopores, [13] graphene-based junction, [14] silicon-based junction, [15] etc.The variety and characteristics of organic molecules have driven many researchers to explore molecular devices. Unsurprisingly, molecular devices also exhibit excellent functional properties. The spin transport properties of a single organic molecule and ferromagnetic electrodes were first theoretically investigated by Emberly, [16] and the spin valve function of molecular junctions were predicted. Yaish [17] et al. reported the Kondo effect and Coulomb blockage in single-atom transistors where the single-molecule Kondo effect is often manifested in spin molecular electronics. Molecular spintronics is an important branch of molecular electronics, and its spin filtering, tunneling magnetoresistance, and giant magnetoresistance effects have been extensively studied. Raymo [18] et al. designed the rotaxane molecular logic gate to make molecular switch Molecular devices have given impetus to the development of new electronic components. The transport process of organic molecules has a significant impact on device performance. Diketopyrrolopyrrole (DPP n , n = 1,2,3,4.) and derivative molecules have been widely explored due to their long-range and efficient transport properties. In this paper, the electronic, optoelectronic, and thermoelectric properties of single diketopyrrolopyrrole molecular devices with different molecular units are investigated. By adjusting t...
