Rubrene

The excited-state energy transfer widely exists in mixed-material systems and devices. The modulation of an electric field on the energy transfer in photoluminescence has been demonstrated. However, to date, no studies on the electric-field modulation of the excited-state energy transfer in organic optoelectronic devices have been reported. Herein, we investigate the effect of an electric field on the energy transfer in the poly( N -vinylcarbazole) (PVK) thin films doped with iridium(iii)[bis(4,6-difluorophenyl)pyridinato-N,C2' ]-tetrakis(1-pyrazolyl)borate (Fir6) and 5,6,11,12-tetraphenylnaphthacene (rubrene) (PVK:Fir6:rubrene) and the corresponding light-emitting diodes...

ConspectusThe crystal structure of organic semiconductors has been regarded as one of the crucial factors for realizing high-performance electronic devices, such as organic field-effect transistors. However, although the control of crystal structures of organic semiconductors has been examined in the last two decades of intensive efforts of the development of organic semiconductors, active measures to control crystal structures enabling high carrier mobility are still limited. In 2016, our research group noticed that regioselective methylthiolation could provide a selective crystal structure change from an ordinary herringbone structure to a pitched π-stacking structure, similar to the crystal structure of rubrene, in the benzo[1,2- b :4,5- b ']dithiophene (BDT) system...

Lateral growth of thin films is crucial for organic electronic devices, such as field-effect transistors. Here, we report a strategy to improve the lateral growth of pentacene films using rubrene as a surfactant-like additive. Atomic force microscopy (AFM) images confirm the enhanced lateral growth with the presence of rubrene, resulting in smooth and enlarged molecule domains in the films in comparison to those without rubrene. Molecular dynamics simulations are conducted to explore the interlayer diffusion of pentacene molecules during the growth...

Three-dimensional electron diffraction (3D-ED) is a powerful technique for crystallographic characterization of nanometre-sized crystals that are too small for X-ray diffraction. For accurate crystal structure refinement, however, it is important that the Bragg diffracted intensities are treated dynamically. Bloch wave simulations are often used in 3D-ED, but can be computationally expensive for large unit cell crystals due to the large number of diffracted beams. Proposed here is an alternative method, the `scattering cluster algorithm' (SCA), that replaces the eigen-decomposition operation in Bloch waves with a simpler matrix multiplication...

5,6,11,12-tetraphenylnaphthacene (rubrene) exhibits resonant energy properties (ES1,rub≈2ET1,rub), resulting in rubrene-based OLED devices that undergo singlet fission (STT) process at room temperature. This unique process gives rise to a distinct magneto-electroluminescence (MEL) profile, differing significantly from the typical intersystem crossing (ISC) process. Therefore, toward investigate charge generation and separation in the interconnector, and the mechanism of charge transport in tandem OLEDs at room temperature using MEL tools...

Metal halide perovskite films have gained significant attention because of their remarkable optoelectronic performances. However, their poor stability upon the severe environment appears to be one of the main facets that impedes their further commercial applications. Herein, a method to improve the stability of flexible photodetectors under water and humidity environment without encapsulation is reported. The devices were fabricated using the physical vapor deposition method (Pulse Laser Deposition & Thermal Evaporation) under high-vacuum conditions...

Materials that undergo singlet fission are of interest for their use in light-harvesting, photocatalysis, and quantum information science, but their ability to undergo fission can be sensitive to local variations in molecular packing. Herein we employ transient absorption microscopy, molecular dynamics simulations, and electronic structure calculations to interrogate how structures found at the edges of orthorhombic rubrene crystals impact singlet fission. Within a micrometer-scale spatial region at the edges of rubrene crystals, we find that the rate of singlet fission increases nearly 4-fold...

Organic semiconductor materials featuring lightweight, and flexibility may play a significant role in various future applications, such as foldable displays, wearable devices, and artificial skin. For developing high-performance organic devices, organic crystals are highly desired, while a remaining fundamental issue is their contact problem. Here, we have grown a high-quality rubrene single crystal by utilizing a simple in-air sublimation technique. The contact characteristics (barrier height and contact resistance) are detail-studied by resist-free transfer electrodes (Au metal or graphene/Au)...

Singlet fission (SF) and its inverse, triplet-triplet annihilation (TTA), are promising strategies for enhancing photovoltaic efficiencies. However, detailed descriptions of the processes of SF/TTA are not fully understood, even in the most well-studied systems. Reports of the photophysics of crystalline rubrene, for example, are often inconsistent. Here we attempt to resolve these inconsistencies using time-resolved photoluminescence and transient absorption spectroscopy of 'pristine' rubrene orthorhombic single crystals...

Interfaces of ferromagnetic/organic material hybrid structures refer to the spin interface that governs physical properties for achieving high spin polarization, low impedance mismatch, and long spin relaxation. Spintronics can add new functionalities to electronic devices by taking advantage of the spin degree of freedom of electrons, which makes understanding the dynamic magnetic properties of magnetic films important for spintronic device applications. Our knowledge regarding the magnetic dynamics and magnetic anisotropy of combining ferromagnetic layer and organic semiconductor by microwave-dependent magnetic measurements remains limited...

Periodic density functional theory was employed to investigate the impact of chemical modifications on the properties of π-conjugated acenedithiophene molecular crystals. Here, we highlight the importance of the β-methylthionation effect, the position of the sulfur atoms of the thiacycle group and their size, and the number of central benzene rings in the chemical modification strategy. Our results show that the introduction of the methylthio groups at the β-positions of the thiophene and the additional benzene ring at the center of the BDT crystal structure are a promising strategy to improve the performance of organic semiconductors, as observed experimentally...

Perovskites have gained popularity both as the active material in photovoltaics and as bulk triplet sensitizers for solid-state triplet-triplet annihilation upconversion (TTA-UC). Prior to widespread implementation into commercial photovoltaics, an in-depth understanding of the environmental influences on device performance is required. To this point, the temperature-dependent structure-function properties of TTA-UC within methylammonium formamidinium lead triiodide (MAFA)/rubrene UC devices are explored. A strong temperature dependence of the underlying UC dynamics is observed, where the maximum UC efficiency is achieved at 170 K, reflecting the competition between triplet diffusion length, diffusion rate, and triplet-triplet encounter events...

Upconversion of near-infrared light into the visible has achieved limited success in applications due to the difficulty of creating solid-state films with high external quantum efficiency (EQE). Recent developments have expanded the range of relevant materials for solid-state triplet-triplet annihilation upconversion through the use of a charge-transfer state sensitization process. Here, we report the single-step solution-processed deposition of a bulk heterojunction upconversion film using organic semiconductors...

The surface molecular doping of organic semiconductors can play an important role in the development of organic electronic or optoelectronic devices. Single-crystal rubrene remains a leading molecular candidate for applications in electronics due to its high hole mobility. In parallel, intensive research into the fabrication of flexible organic electronics requires the careful design of functional interfaces to enable optimal device characteristics. To this end, the present work seeks to understand the effect of surface molecular doping on the electronic band structure of rubrene single crystals...

Fiber optic communication is becoming the central pillar of modern high-speed communication technology, which involves the abundant fiber components. Currently, most of photodetectors are fabricated on the silicon chip, so mass fiber-to-chip interfaces increase the complexity of advanced optoelectronic system, and also grow the risk of optical information loss. Here, we report an all-fiber organic phototransistor by employing rubrene single crystal and few-layer graphene to realize the "plug-to-play" operation...

For the last two decades, research has addressed whether the glass transition temperature and the molecular motions on the surface of organic films are significantly different from those inside the bulk glasses. It is reported that the surface of the photochromic diarylethene film prepared by vacuum deposition has fluidity and the vacuum deposition of small amount of rubrene molecules induces surface tension fluctuations, generating dents due to the Marangoni flow in nanoscale. The depth of the dents increases in proportion to these radii for the colorless diarylethene film with a bulk glass transition temperature (Tg) close to room temperature...

Although the effect of the electron blocking layer (EBL) material, deoxyribonucleic acid (DNA), on the electroluminescence (EL) performance of organic light-emitting diodes (OLEDs) has been studied, the process of DNA regulation of exciton recombination region within the device is still unclear. Herein, devices with and without EBL were fabricated using different DNA spin-coating speeds, and the photoelectric performance of device were measured. By using DNA compounded with CTMA as the EBL and hole buffer layer, so-called BioLEDs...

Although the effect of the conductive polymers PEDOT:PSS on the electroluminescence performance of doped-type organic light-emitting diodes (OLEDs) has been studied, the process of PEDOT:PSS regulation of exciton recombination region and concentration within the deoxyribonucleic acid (DNA)-based doped-type BioLEDs is still obscure. In this study, we fabricated Bio-devices with and without PEDOT:PSS using varying spin-coating speeds of PEDOT:PSS. The Alq3 :Rubrene-based BioLEDs achieve higher luminance (44,010 cd/m2 ) and higher luminance efficiency (8...

Organic semiconductors have opened up many new electronic applications, enabled by properties like flexibility, low-cost manufacturing, and biocompatibility, as well as improved ecological sustainability due to low energy use during manufacturing. Most current devices are made of highly disordered thin-films, leading to poor transport properties and, ultimately, reduced device performance as well. Here, we discuss techniques to prepare highly ordered thin-films of organic semiconductors to realize fast and highly efficient devices as well as novel device types...

Energy transfer processes may be engineered in van der Waals heterostructures by taking advantage of the atomically abrupt, Å-scale, and topologically tailorable interfaces within them. Here, we prepare heterostructures comprised of 2D WSe2 monolayers interfaced with dibenzotetraphenylperiflanthene (DBP)-doped rubrene, an organic semiconductor capable of triplet fusion. We fabricate these heterostructures entirely through vapor deposition methods. Time-resolved and steady-state photoluminescence measurements reveal rapid subnanosecond quenching of WSe2 emission by rubrene and fluorescence from guest DBP molecules at 612 nm (λexc = 730 nm), thus providing clear evidence of photon upconversion...