Polymer solar cells are one of the promising energy sources because of the easy solution-processable production with large area at a low cost without toxicity. Among the polymer materials, a donor-acceptor conjugated copolymer PTB7 has been extensively studied because of the typical high-performance polymer solar cells. Here, we show operando direct observation of charge accumulation in PTB7:PCBM blend solar cells from a microscopic viewpoint using electron spin resonance spectroscopy. The accumulation of ambipolar charges in the PTB7-based cells is directly observed for the first time, which shows a clear correlation with the performance deterioration during device operation. The sites of the ambipolar charge accumulation are elucidated at the molecular level, whose information would be useful for improving the cell durability in addition to the performance improvement.

A low band-gap polymer, PTB7-Th, is one of the typical p-type semiconductors among the next-generation solar-cell materials that have achieved power conversion efficiencies of over 10%. However, the internal deterioration mechanism of high-efficiency polymer solar cells such as PTB7-Th-based cells is still an open issue and has been extensively studied. Here, we report a study with operando electron spin resonance (ESR) spectroscopy for PTB7-Th polymer solar cells with an n-type semiconductor PC71BM to clarify the internal deterioration mechanism at a molecular level. We have directly observed ambipolar charge accumulation with a face-on molecular orientation in the cells under simulated solar irradiation using an operando light-induced ESR technique. Moreover, we have found a clear correlation between the charge accumulation and performance deterioration of the cells. The charge accumulation sites have been clarified by the ESR analysis and density functional theory calculation. The prevention of such charge accumulation on the basis of the present finding would be important for the commercialization of high-efficiency polymer solar cells.

Noise sources of 70-nm NMOS transistors the model by presenting a noise parameter simulation of were extracted to reveal the channel noise is dominant up to MOS transistors. 26 GHz. Gate induced noise increased in proportion to , however, its level was 1 to 2 orders of magnitude lower than II. NOISE PARAMETER MEASUREMENT the channel noise. A new approach to accurately capturing In this study, ATN NP-5 (from 0.5 to 6 GHz) and the behavior of thermal noise by compensating for the Maury ATS (from 4 to 26 GHz) systems were used for discrepancy between extracted and simulated channel noise noise parameter (NFmin, Rn, Fopt) measurement. NMOS through the addition of an excess noise source was l-, , Xdemonstrated. The excess noise source was incorporated into transistors with physical gate lengths of 70 nm and fixed our RFMOS model, which enabled us to accurately simulate finger width of 2.5 pm were characterized by the systems. noise parameters. By using this technique the noise figure ofThe total gate width, Wtotai, was varied from 10 to 160 ptm.

Ferrite films with a chemical composition Ni 0 2 Zn 0 3 Fe 2 O 4 of 3 m thickness were deposited at 90 C from an aqueous solution directly on the inner ground and/or the power source layers of the following two different types of four-layered printed wiring boards (PWBs), in order to suppress the electromagnetic noise emission due to high frequency currents generated in the inner layers. PWB (a), which is the most commonly used structure, is composed of two outer signal layers, an inner ground layer, and an inner power layer. PWB (b) is composed of two outer signal layers, which contain the power supply lines as well, and two inner ground layers. Radiated emission from the ferrite film-embedded PWB (a) was successfully suppressed to be 2 to 5 dB lower than that without the ferrite film. This tendency became more prominent with increasing frequency. A similar noise suppression effect was also observed for the ferrite film-embedded PWB (b), up to 4 dB. This suggests that we can suppress radiated emission also in the case where the ground and the power planes are not placed symmetrically in the inner layers. The frequency dependence of radiated noise suppression effect by the ferrite film corresponded to the frequency dependence of transmission attenuation power ratio ( loss in ), i.e. the suppression effect upon conducted noise due to magnetic loss characteristics of the film. This indicates that the suppression of radiated emission from the four-layered PWBs was due to the attenuation of GHz-range noise current in the ground and/or the power layers.Index Terms-Electromagnetic radiated emission, ferrite-plated film, four-layered printed wiring board, transmission attenuation power ratio.

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