Ultra-low reflectance, high absorption microcrystalline silicon nanostalagmite
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NANO EXPRESS
Open Access
Ultra-low reflectance, high absorption microcrystalline silicon nanostalagmite Subramani Thiyagu1, Balasubramaniam Parvathy Devi1, Zingway Pei1*, Yu-Hung Chen2 and Jun-Chin Liu2
Abstract In this work, microcrystalline silicon nanostalagmite [μc-SiNS] arrays have been successfully fabricated on glass by catalytic etching process through a template. The template, polystyrene [PS] nanospheres, with diameter and density of 30 to approximately 50 nm and 1010/cm2, respectively, was obtained by a modified nanophase separation of PS-containing block copolymer. The length of μc-SiNS could be controlled by the duration of etching time. The μc-SiNS exhibits ultra-low reflection approximately 0.3% and absorption around 99% over 300 to 800 nm in wavelength. Reflection is also suppressed for a wide range of angles of incidence in wide range of wavelength. This indicates the extensive light-trapping effect by the μc-SiNS and could possibly harvest a large amount of solar energy at infrared regime. Keywords: ultra-low reflection, microcrystalline silicon, nanostalagmite, polystyrene nanospheres, light trapping
Introduction Silicon thin film solar cells are promising candidates for future generations of photovoltaic devices [1,2]. They offer cost effectiveness and the possibility of deposition on flexible substrates [3-5]. However, the efficiency of thin film Si solar cell is relatively low compared to crystalline solar cell. The low absorption rate, relative poor material quality and narrow absorption spectra are the major factors. In the past few years, there is an enormously growing interest in the development of nanostructure materials to improve the light-harvesting efficiency for achieving high-efficiency Si thin film solar cell while maintaining low cost. Feasible silicon nanostructures such as silicon nanowires [SiNWs] have gained much attention due to their unique properties and possible applications in the fields of nanoelectronics [6-9], nanooptoelectronics [9,10], nanophotovolatics [11-17] and for sensor applications [18]. SiNWs are usually produced via vapour-liquid-solid [VLS] growth mechanism [19], which introduced one-dimensionality growing of nanostructure by a metal nanocatalyst droplet containing gases such as silane or grow from the gas phase by supplying Si vapour. However, the VLS growth * Correspondence: [email protected] 1 Graduate Institute of Optoelectronic Engineering, Department of Electrical Engineering, National Chung Hsing University, Taichung, Taiwan, 40227, Republic of China Full list of author information is available at the end of the article
mechanism generally requests high temperature that is not the adequate method for Si thin film nanostructure. In particular, the microcrystalline silicon [μc-Si] solar cells grown on glass or plastic substrate cannot sustain high temperature. Nanoelectronics and nanooptoelectronics require vertically oriented, length tuneable and high density silicon nanostructures to obtain processing compatibility. To obtain such nanos
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