Browsing by Author "Cheng, Yu-Chih"

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Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes
(2011-02-14)
Hsu, Min-Hsiang
;
Yu, Peichen
;
Huang, Jen-Hsien
;
Chang, Chia-Hua
;
Wu, Chien-Wei
In this paper, we present evidence of balanced electron and hole transport in polymer-fullerene based solar cells by means of embedded indium-tin-oxide nanoelectrodes. Enabled by a controllable electrochemical deposition, the individual nanoelectrodes are uniformly enclosed by a poly (3,4-ethylenedioxythiophene) hole-conducting layer, allowing a relatively short route for holes to reach the anode and hence increasing the effective hole mobility. Consequently, the power conversion efficiency and photogenerated current are maximized with a deposition condition of 50 mu C, where the ratio of the electron to hole mobility is nearly unity. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556565]
Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes (vol 98, 073308, 2011)
(2011-03-14)
Hsu, Min-Hsiang
;
Yu, Peichen
;
Huang, Jen-Hsien
;
Chang, Chia-Hua
;
Wu, Chien-Wei
Characteristics of large-scale nanohole arrays for thin-silicon photovoltaics
(2014-04-01)
Chen, Ting-Gang
;
Yu, Peichen
;
Chen, Shih-Wei
;
Chang, Feng-Yu
;
Huang, Bo-Yu
Nanostructured crystalline silicon is promising for thin-silicon photovoltaic devices because of reduced material usage and wafer quality constraint. This paper presents the optical and photovoltaic characteristics of silicon nanohole (SiNH) arrays fabricated using polystyrene nanosphere lithography and reactive-ion etching (RIE) techniques for large-area processes. A post-RIE damage removal etching is subsequently introduced to mitigate the surface recombination issues and also suppress the surface reflection due to modifications in the nanohole sidewall profile, resulting in a 19% increase in the power conversion efficiency. We show that the damage removal etching treatment can effectively recover the carrier lifetime and dark current-voltage characteristics of SiNH solar cells to resemble the planar counterpart without RIE damages. Furthermore, the reflectance spectra exhibit broadband and omnidirectional anti-reflective properties, where an AM1.5 G spectrum-weighted reflectance achieves 4.7% for SiNH arrays. Finally, a three-dimensional optical modeling has also been established to investigate the dimension and wafer thickness dependence of light absorption. We conclude that the SiNH arrays reveal great potential for efficient light harvesting in thin-silicon photovoltaics with a 95% material reduction compared to a typical cell thickness of 200 mu m. Copyright (c) 2012 John Wiley & Sons, Ltd.
FABRICATION AND MODELING OF LARGE-SCALE SILICON NANOWIRE SOLAR CELLS FOR THIN-FILM PHOTOVOLTAICS
(2012)
Cheng, Yu-Chih
;
Chen, Ting-Gang
;
Chang, Feng-Yu
;
Huang, Bo-Yu
;
Pan, Huai-Te
Nanostructured crystalline silicon is promising for thin photovoltaic devices due to reduced material usage and wafer quality constraint. In this study, a simple and cost-effective method is presented for producing large-area silicon nanowire (SiNW) arrays with various lengths by employing the polystyrene nanosphere lithography and the metal-assisted chemical etching (MACE). The nanowire structure exhibits broadband and omnidirectional antireflection properties, where the lowest AM1.5G-spectrum-weighted reflectance of SiNW arrays is 4.38%, compared to 8.84% of the conventional single layer antireflection coating (SLARC). Next, we made SiNW array structures into solar cells and its power efficiency achieved 10.8%. Afterward, the SiNW array solar cells were analyzed by external and internal quantum efficiency measurement which shows the device performance primarily limited by direct and indirect interfacial recombination of charge carriers. We further develop a modeling technique based on three-dimensional (3) optical and two-dimensional (20) electrical simulations which are tailored for the nanostructured silicon photovoltaic devices. The optical simulation employs a rigorous couple wave analysis (RCWA) technique to calculate the distribution of electromagnetic field in order to obtain the generation rate within the nanostructure. Next, an electrical calculation is based on a 20 self-consistent drift-diffusion and Poisson solver using a finite element method (FEM). We investigate the influence to the device performance of carrier diffusion length with three different structures. The simulation results show that a short diffusion length does not seriously deteriorate the short-circuit current density and power conversion efficiency of a core-shell PN junction solar cell compared to the conventional planar structure. Our work suggests that SiNW solar cells can achieve efficient light harvesting and photoelectric conversion with less and lower-grade materials than the conventional technology, which is promising for thin silicon photovoltaics.
Ubiquitous carrier harvesting in organic solar cells with embedded indium-tin-oxide nano-electrodes
(2013-11-01)
Hsu, Min-Hsiang
;
Chen, Po-Han
;
Yu, Peichen
;
Huang, Jen-Hsien
;
Chang, Chia-Hua
Bulk heterojunction in organic solar cells allows adequate interfaces for the dissociation of photo-generated excitons. However, the intermixed donor- and acceptor-like materials do not guarantee successful carrier transport and collections. In this work, we demonstrate ubiquitous carrier harvesting characteristics by using embedded indium-tin-oxide nano-electrodes (NEs) with a conformal electro-polymerized coating of a hole conducting layer. Compared to its planar electrode counterpart, this device exhibits internal quantum efficiency insensitive to the distribution of carrier generation, as determined by angle-resolved absorption spectroscopy and photocurrent characteristics. The ubiquitous carrier harvesting characteristics offer a viable solution to organic thin-film devices fabricated on flexible substrates or operated under diffused ambient light. (C) 2013 Elsevier B.V. All rights reserved.