2,4,6-trimethylphenyl)amine] (PTAA) [7] as the hole transport material (HTM). However, there is still a gap of more than 5% between the record efficiency and the maximum efficiency of thermally stable PSCs. So far, the thermal stability of perovskite absorber materials has been improved by engineering perovskite composition; both cation [8][9][10][11] and halide [10][11][12][13] composition engineering have been conducted. Also, 2D-3D incorporated perovskite materials for high thermal stability have been recently suggested. [14][15][16] On the other hand, multication approach is one of the promising ways to achieve highly efficient PSCs. [7,17] However, at the same time, it is more and more difficult to understand and control such a large number of components for highly efficient and highly stable PSCs. In case of our previous study for quadruple cation PSCs, [7] seven components of formamidinium (FA), methylammonium (MA), Cs, Rb, Pb, I, and Br should be controlled. Furthermore, not only effect of single element but also combination effect of these elements should be important. Thus, careful studies are required for further development. Indeed, even though more and more studies have been reported on multication approach, [18][19][20][21] there are still no reports of PSCs that meets international standard (IEC 61215); 85 °C/85% relative humidity (RH) stress test with high efficiency. Here we focus on the dependence of device thermal stability on perovskite composition by using state-of-the-art highly efficient PSCs (≈20%) to achieve compatibility of high efficiency and high thermal stability.We tested the thermal stability of devices with a structure of indium tin oxide (ITO)/compact titanium dioxide (TiO 2 )/ mesoporous TiO 2 /perovskite/PTAA/gold (Au). The starting perovskite composition used here was Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb (I 0.83 Br 0.17 ) 3 because this composition has been reported to display high efficiency and high operational stability. [17] We chose PTAA as the HTM because its high efficiency [22][23][24] and high thermal stability [7] have been reported respectively. In addition, we used a low doping concentration of 3 mol% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in PTAA in this experiment to minimize any adverse effects of the additives on the device thermal stability reported so far. [25][26][27] First, we examined the relationship between efficiency and thermal stability for devices with different PbI 2 ratios in the Perovskite solar cells have received great attention because of their rapid progress in efficiency, with a present certified highest efficiency of 23.3%. Achieving both high efficiency and high thermal stability is one of the biggest challenges currently limiting perovskite solar cells because devices displaying stability at high temperature frequently suffer from a marked decrease of efficiency. In this report, the relationship between perovskite composition and device thermal stability is examined. It is revealed that Rb can suppress the growth of PbI 2 even un...

Electron field emission from boron nitride nanofilm and its application to graphite nanofiber

GaN layers are grown on sapphire substrates with AlN buffer layers by the metalorganic chemical vapor deposition method. GaN layers are doped with Si. The electron density of the n-type GaN is 2×1017 cm−3. It is found that the GaN surface is etched with hydrogen (H2) plasma produced by supplying microwave power leading to the formation of the roughened surface of GaN. A variation in the surface morphology occurs due to microwave power and gas pressure. Field emission measurements are carried out for GaN with various surface morphologies. It is observed that the turn-on electric field decreases with increasing surface roughness of the GaN. A turn-on electric field of the electron emission is estimated to be as low as 12.4 V/μm.

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A synchrotron X-ray diffractometer incorporating a pulsed field magnet for high fields up to 40 T has been developed and a detailed description of this instrument is reported. The pulsed field magnet is composed of two coaxial coils with a gap of 3 mm at the mid-plane for passage of the X-rays. The pixel detector PILATUS 100K is used to store the diffracted X-rays. As a test of this instrument, X-ray diffraction by a powder sample of the antiferromagnet CoO is measured below the Néel temperature. A field-dependent lattice distortion of CoO due to magnetostriction is observed up to 38 T.

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Lead halide perovskite is a candidate for nextgeneration solar cells. Improvements in photovoltaic conversion efficiency and cell durability in different environments, such as moisture, heat, and light, are pertinent for practical use. Researchers must solve the problem of light-induced degradation (LID) of perovskite solar cells. Oxygen accelerates LID. However, a buffer layer between the electron transport layer (ETL)/ perovskite interface suppresses LID. Herein, we report the influence of oxygen and the buffer layer on LID at the perovskite [(FA 0.83 MA 0.17 ) 0.95 Cs 0.05 (I 0.95 Br 0.05 ) 3 with 2.5 mol % RbI additive]/ hole transport layer (HTL) and ETL/perovskite interfaces by hard X-ray photoelectron spectroscopy. We confirmed that oxygen accelerated the increase in the fraction of neutral iodine at the perovskite/HTL interface after light illumination and the introduction of a self-assembled monolayer as the buffer layer greatly suppressed the increase in the fraction of neutral lead at the ETL/perovskite interface, suggesting that photoelectrochemical reactions at the interfaces play an important role in the LID of perovskite solar cells.

No abstract