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To clarify the role of buffer layer in organic solar cells (OSCs), the electronic properties of bathocuproine (BCP)/Mg interface were systematically investigated by using ultraviolet photoemissions spectroscopy, high-resolution X-ray photoemission spectroscopy, angle-resolved X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results show there are gap states at the interface, which are caused by the interaction between BCP and Mg. The formation of Mg-N bond was found at the interface. The NEXAFS measurements show that BCP molecules for 1-2 monolayers are lying-down on the substrate, whereas orient randomly for thick BCP layer. It was supposed that the gap states and the highly-ordered orientation of thin BCP layer are the reasons for improving the performance of OSC with BCP buffer layer and low work function metal cathode. [ABSTRACT FROM AUTHOR]

The exploration of new physical properties for various THz-based applications, such as THz-wave sensing, modulation, and imaging devices, is a key challenge in the research on organic–inorganic hybrid perovskite materials. These THz-based applications require satisfactory, sensitive, and stable absorption properties with values between 0.5 and 3 THz. To achieve these properties, candidate materials should possess a purified structure that induces regular and fixed phonon modes without any defects or impurities. CH3NH3PbBr3, an organic–inorganic hybrid perovskite thin film produced by a sequential vacuum evaporation method on a flexible PET substrate, was investigated in this study. Although the thin film contains only molecular defects related to CH3NH2 incorporated into the perovskite structure, our THz-wave absorption measurement and first-principles simulation confirmed that these molecular defects do not influence the three phonon modes originating from the transverse vibration (0.8 THz), the longitudinal optical vibrations (1.4 THz) of the Pb–Br–Pb bonds, and the optical Br vibration (2.0 THz). After spin-casting an ultrathin PTAA polymer protective layer (5 nm) on the hybrid perovskite thin film, it was additionally observed that there was no significant effect on the phonon modes. Thus, this novel flexible organic–inorganic hybrid perovskite material is a potential candidate for THz-based applications. NPG Asia MaterialsOptical materials: a new choice for security imaging A material useful for security imaging has been identified by an international team of scientists. Radiation between the infrared and microwave parts of the electromagnetic spectrum can pass through clothing. This so-called terahertz radiation is valuable for security screening technology as it can identify a wider range of materials than metal detectors and is much quicker than a manual pat-down. A team led by Young-Kyun Kwon from Kyung Hee University, Seoul, South Korea, and Min-Cherl Jung from the University of Tsukuba, Ibaraki, Japan, demonstrated that a material already used with great success in optoelectronic and solar cell applications, known as an organic–inorganic hybrid perovskite, also has useful terahertz properties. The team created thin films of this material on a flexible substrate and showed that it absorbed radiation at fixed terahertz frequencies. Phonon modes of CH3NH3PbBr3 hybrid perovskite thin film. [ABSTRACT FROM AUTHOR]

Working principle of OM. [Display omitted] • It resolves problems such as burdensome preprocessing method order, fluctuating optimization outcomes, and a lack of sufficient statistical information. • It can significantly extract spectrum information and develop high valuable calibration models. • It can offer various types of crucial statistical data to guarantee the objectivity of the outcomes. • It is simple to use, and the results optimized by it are simple to interpret. • It can therefore be utilized to efficiently eliminate a lot of repetitive manual labor. An essential step in the application of near infrared spectroscopy technology is the spectrum preprocessing. A reasonable implementation of it ensures that the effective spectral information is correctly extracted and, also that the model's accuracy is increased. However, some analysts' research still uses the manual approach of trial and error, particularly those less skilled ones. Previous papers have provided preprocessing optimization algorithms for NIR, but there are still some problems that need to be resolved, such as the unwieldy sequence determination of preprocessing method or, the fluctuated optimization outcomes or, lack of sufficient statistical information. This research suggests a spectrum auto-analysis methodology named self-expansion full information optimization strategy, a new powerful open-source technique for concurrently addressing all of these above issues simultaneously. For the first time in the field of chemometrics, this algorithm offers a reliable and effective automatic near infrared auto-modelling method based on the statistical informatics. With the aid of its built-in modules, such as information generators, spectrum processors, etc., it is able to fully search the common preprocessing techniques, which is determined by Monte Carlo cross validation. Then the final ensemble calibration model is built by employing the optimized preprocessing schemes, along with the wavelength variables screening algorithm. The optimization strategy can offer the user objective useful statistics information created throughout the modeling process to further examine the model's effectiveness. The results demonstrate that the suggested method can easily and successfully extract spectrum information and develop calibration models by putting it to the test on two groups of actual near-infrared spectral data. Additionally, this optimization strategy can also be applied to other spectrum analysis areas, such Raman spectroscopy or infrared spectroscopy, by changing a few of its parameters, and has extraordinary application value. [ABSTRACT FROM AUTHOR]