Browsing by Author "Shirai, H."

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Poly(3,4ethylenedioxythiophene): poly(styrenesulfonate)/GaAs hybrid solar cells with 13% power conversion efficiency using front- and back-surface field
(2015-09-21)
Lin, C. H.
;
Sun, K. W.
;
Liu, Q. M.
;
Shirai, H.
;
Lee, C. P.
Planar hybrid solar cells based on bulk GaAs wafers with a background doping density of 1016 cm(-3) and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) demonstrated an excellent power conversion efficiency of 8.99%. The efficiency of the cell was enhanced to 9.87% with a back-surface field feature using a molecular beam epitaxially grown n-type GaAs epi-layer. The efficiency and fill factor reach 11.86% and 0.8 when an additional p + GaAs epi-layer is deposited on the surface of the solar cells, which provides a front-surface field. The interface between the high-and low-doped regions in the polymer/GaAs and GaAs formed an electric field that introduced a barrier to minority carriers flow to the substrate and effectively reduced front surface carrier recombination, thereby enhancing light-generated free carrier collection efficiency and open-circuit voltage. Compared with the device without the front-and back-surface field, the fill factor and open-circuit voltage of the hybrid solar cell were improved from 0.76 to 0.8 and from 0.68 V to 0.77V, respectively. The highest efficiency reaches a record 13% when the Zonyl fluorosurfactant-treated PEDOT: PSS is used as a hole-transporting conducting layer for hybrid cells. (C) 2015 Optical Society of America
Single-shot detection of mid-infrared spectra by chirped-pulse upconversion with four-wave difference frequency generation in gases
(2013-07-29)
Nomura, Y.
;
Wang, Y. -T.
;
Kozai, T.
;
Shirai, H.
;
Yabushita, A.
Single-shot detection of ultrabroadband mid-infrared spectra was demonstrated by using chirped-pulse upconversion technique with four-wave difference frequency generation in gases. Thanks to the low dispersion of the gas media, the bandwidth of the phase matching condition of the upconversion process becomes very broad and the entire mid-infrared spectrum spanning from 200 to 5500 cm(-1) was upconverted by using a 10 ps chirped pulse to visible wavelength radiation, which was detected with a conventional visible dispersive spectrometer. This method was demonstrated by the successful measurement of infrared absorption spectra of organic polymer films. (C) 2013 Optical Society of America