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We report the time-profile of the THz wave from GaAs-based photovoltaic devices depending on its structure. Bias dependence of the THz waveforms indicates that the picosecond drift current depends on the device structure even with the same depletion layer condition. This result is critical for the photovoltaic device characterization with the measurement of the THz radiation.
Hybrid lead halide perovskites, such as methylammonium lead halides CH3NH3PbX3 (MAPbX3, X = I, Br, Cl), are emerging as an excellent class of materials for various optoelectronic applications including solar cells, light-emitting diodes, lasers, and photodetectors [1,2]. As for these perovskite-based devices, deep understanding of transport properties of excitons and charge carriers in perovskite...
Recently, metal-halide perovskite semiconductors have been extensively studied because of their potential use in solar-cell, photodetector, light-emitting-diode, and laser applications. In particular, perovskite nanocrystals (NCs) are gaining more and more attention because their optical spectra can be manipulated by changing the NC size and the halogen composition [1]. In contrast to the conventionally...
We performed time-resolved terahertz reflection spectroscopy in a GaAs p-i-n device. While p- and n-doped layers are not transparent in low frequency region, we observed the characteristic spectral modulation under the photoexcitation. From the spectral analysis, we quantitatively evaluate the carrier density in the active layer with low concentration. We propose this scheme for a new tool for evaluating...
The effects of alkali doping (Na, Li, K) on the carrier transport in Cu2ZnSn(S, Se)4 (CZTSSe) thin films have been studied systematically using time-resolved THz spectroscopy. Na and Li doping seem to have no influence on the carrier mobility, whereas K doping leads to a noticeable decrease. In addition, we found that Na doping increases the lifetime of photocarriers, but Li and K doping do not. Consequently,...
We studied the carrier multiplication efficiency in bulk silicon using optical-pump/THz-probe spectroscopy. By the close analysis of the time resolved data, we observed the enhancement of the quantum efficiency due to carrier multiplication for incident photon energy above 4.1 eV. It agrees well with the results of photo current measurements. We believe that the present results enable us to correlate...
A real-time noninvasive and unconstrained method is proposed to determine the respiratory rhythm and pulse rate with an under-pillow sensor during sleep. The sensor is composed of two fluid-filled polyvinyl tubes set in parallel and sandwiched between two acrylic plates. One end of each tube is hermetically sealed, and the other end is connected to one of two pressure sensors. Inner pressure in each...
Intrinsic microcrystalline silicon (/spl mu/c-Si:H) grown by SiH/sub 4/-H/sub 2/ plasma at different growth temperatures have been applied to superstrate-type p-i-n solar cells in order to investigate effect of i-layer growth temperature (T/sub s/) on p/i interface properties. Although high quality /spl mu/c-Si:H films (low defect density and large grain size) are obtained at T/sub s//spl sim/250/spl...
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