Toshinori Matsushima

Current density–voltage (J-V) characteristics of hole-only devices using indium tin oxide (ITO) anode and N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layers were measured with various thicknesses of a molybdenum trioxide (MoO3) buffer layer inserted between ITO and α-NPD. The device with a 0.75-nm-thick MoO3 layer forms Ohmic hole injection at the ITO∕MoO3∕α-NPD interfaces and J-V characteristics of this device are controlled by a space-charge-limited current. Results o

A very high hole mobility of 15 cm² V^-1 s^-1 along with negligible hysteresis are demonstrated in transistors with an organic-inorganic perovskite semiconductor. This high mobility results from the well-developed perovskite crystallites, improved conversion to perovskite, reduced hole trap density, and improved hole injection by employing a top-contact/top-gate structure with surface treatment and MoO_x hole-injection layers.

Organic–inorganic halide perovskites are promising as the light absorber of solar cells because of their efficient solar power conversion. An issue frequently occurring in perovskite solar cells (PSCs) with a hole transport layer of N,N ‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (spiro‐OMeTAD) is a quick performance degradation at high temperature. Herein, it is discovered that postdoping of the spiro‐OMeTAD layer by iodine released from the perovskite layer is one possible mechanism for th

Quasi-2D perovskites have attracted wide attention as the emitter of light-emitting diodes (LEDs) in recent years because of the ease of obtaining high external quantum efficiencies (EQEs). However, the quick degradation under continuous operation and significant EQE roll-off at high current densities are issues that need to be overcome for future practical applications using quasi-2D perovskite LEDs (PeLEDs). In this context, we discuss the mechanism of the degradation and EQE roll-off on the b

We show that the performance of organic light-emitting diodes (OLEDs) is markedly improved by optimizing the thickness of a hole-injection layer (HIL) of molybdenum oxide (MoO3) inserted between indium tin oxide and N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD). From results of the electroluminescence (EL) characteristics of OLEDs with various thicknesses of a MoO3 HIL, we found that the OLED with a 0.75-nm-thick MoO3 HIL had the lowest driving voltage and the highest pow

Organic light-emitting diodes with p-doped alpha-sexithiophene and n-doped phenyldipyrenylphosphine oxide carrier transport layers are fabricated. In the doped diodes, the authors demonstrate an extremely low driving voltage of 2.9V at a current density of 100mA∕cm2 and very high luminance at a low driving voltage: 1000cd∕m2 at 2.4V, 10000cd∕m2 at 2.8V, and 920000cd∕m2 at 4.5V. Such lowered driving voltages and enhanced luminance characteristics are attributed to the generation of free charge ca

Organic–inorganic metal halide perovskite solar cells (PSCs) are one of the emerging technologies in photovoltaic research. The certified maximum power conversion efficiency (PCE) of PSCs has reached as high as 25%. In particular, the development of hole transport layer (HTL) materials plays a key role in increasing PCEs. Among a vast number of HTL materials developed to date, the most common HTL material is 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), be

Large electron injection barriers and electrode degradation are serious issues that need to be overcome to obtain n-channel operation in field-effect transistors with an organic-inorganic layered perovskite (C6H5C2H4NH3)2SnI4 semiconductor. By employing low-work-function Al source/drain electrodes and by inserting C60 layers between the perovskite semiconductor and the Al electrodes to reduce the injection barrier and to suppress the electrode degradation, we demonstrate n-channel perovskite tra

Current density-voltage characteristics of hole-only devices are influenced by thicknesses of molybdenum dioxide (MoO2) and molybdenum trioxide (MoO3) as buffer layers. A space-charge-limited current of N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) is observed in a wide range of MoO2 thicknesses from 0.25 to 10 nm and at a specific MoO3 thickness of 0.75 nm. Charge transfer characteristics at interfaces of MoO2/α-NPD and MoO3/α-NPD are investigated from changes in fluores

We have found that molybdenum dioxide (MoO2) is an excellent dopant for enhancing electrical conductivities in organic hole-transporting layers. We fabricated hole-only devices with an alpha-sexithiophene (α-6T) layer doped with MoO2 at various concentrations to investigate how doping MoO2 into the α-6T layers influences the hole-injection and hole-transport characteristics of these layers. We observed a marked increase in electrical conductivity as a result of the MoO2 doping. The 30-mol % MoO2

Abstract Quasi‐2D metal halide perovskite films are promising for efficient light‐emitting diodes (LEDs), because of their efficient radiative recombination and suppressed trap‐assisted quenching compared with pure 3D perovskites. However, because of the multidomain polycrystalline nature of solution‐processed quasi‐2D perovskite films, the composition engineering always impacts the emitting properties with complicated mechanisms. Here, defect passivation and domain distribution of quasi‐2D pero

The authors investigated the influence of O2 and H2O molecules absorbed in carbon-60 (C60) films on their electron trap and n-type field-effect transistor (FET) characteristics. Electron traps in the C60 films were directly measured using a thermally stimulated current (TSC) technique. The TSC results demonstrate that the absorption of O2 and H2O molecules in the C60 films induced an increase in the electron trap concentration, which degrades C60 FET characteristics. By annealing the C60 films a

The material 2-phenylethylammonium tin iodide perovskite (C6H5C2H4NH3)2SnI4 [abbreviated as (PEA)2SnI4] has shown promising performance as a polycrystalline semiconductor for field-effect transistors (FETs). However, grain boundaries and structural disorder in polycrystalline films limit performance, and so the fundamental upper bounds of the material are yet to be studied. Here, we prepared large crystals of (PEA)2SnI4 for FETs and demonstrated carrier mobilities of 40 cm2 V−1 s−1 or higher, al