Search

The π-conjugated rigid molecule Bph is a candidate for use as a channel system of single-molecule transistors. In this first-principles study, the practicality of the chemical modification of the channel molecule Bph for enhancing stability and improving performance is discussed. The insertion of methylene groups into the edges of a channel is suggested to enhance the stability of the cross-linking structures between electrodes because of the relaxation of S bonds. The calculation of electronic states and transmission indicates the sufficient on current of the methylene-inserted Bph derivative (Bph–CH2) in transistors through resonant tunneling. These results suggest the practicality of inserting methylene groups as a method of modifying channel molecules for achieving high stability and large on currents to realize single-molecule transistors. [ABSTRACT FROM AUTHOR]

The energetic driving force for electron transfer must be minimized to realize efficient optoelectronic devices including organic light‐emitting diodes (OLEDs) and organic photovoltaics (OPVs). Exploring the dynamics of a charge‐transfer (CT) state at an interface leads to a comprehension of the relationship between energetics, electron‐transfer efficiency, and device performance. Here, we investigate the electron transfer from the CT state to the triplet excited state (T1) in upconversion OLEDs with 45 material combinations. By analyzing the CT emission and the singlet excited‐state emission from triplet–triplet annihilation via the dark T1, their energetics and electron‐transfer efficiencies are extracted. We demonstrate that the CT→T1 electron transfer is enhanced by the stronger CT interaction and a minimal energetic driving force (<0.1 eV), which is explained using the Marcus theory with a small reorganization energy of <0.1 eV. Through our analysis, a novel donor–acceptor combination for the OLED is developed and shows an efficient blue emission with an extremely low turn‐on voltage of 1.57 V. This work provides a solution to control interfacial CT states for efficient optoelectronic devices without energy loss. [ABSTRACT FROM AUTHOR]

Despite the rapid progresses in the field of organic semiconductors, aided by the development of high-mobility organic materials, their high carrier mobilities are often unipolar, being sufficiently high only for either electrons or holes. Yet, the basic mechanisms underlying such significant mobility asymmetry largely remains elusive. We perform angle-resolved photoelectron spectroscopy to reveal the occupied band structures and the many-body interactions for low-mobility hole carriers in a typical n-type semiconductor perylene diimide derivative. The band dispersion exhibits strong renormalization to the calculated non-interacting electronic structure. The analysis including many-body interactions elucidate that the significant mass enhancement can be understood in terms of strong charge–phonon coupling, leading to an important mechanism of polaron band transport of low intrinsic carrier mobility in organic semiconductors. [ABSTRACT FROM AUTHOR]