Antireflective silicon surface with vertical-aligned silicon nanowires realized by simple wet chemical etching processes

Abstract

Silicon antireflection is realized with vertical-aligned SiNWs by using improved metal-induced etching technique. The spectral responses of the transmission, reflection, and absorption characteristics for the SiNWs of different lengths are investigated. In order to realize short SiNWs to provide sufficiently low reflection, a post chemical etching process is developed to make the nanowires have a larger length fluctuation and/or tapered structure. The use of short SiNWs can allow a faster process time and avoid the sub-bandgap absorption that frequently occurs in long nanowires. Short SiNWs can also provide more compatible material structure and fabrication procedures than long ones can for applying to make optoelectronic devices. Taking the applications to solar cells as examples, the SiNWs fabricated by the proposed technique can provide 92% of solar weighted absorption with about 720 nm long wires because of the resultant effective graded index and enhanced multiple optical scattering from the random SiNW lengths and tapered wires after KOH etching.

Fabrication and Photosensitivity of CdS/Silicon Nanoscrew Photoresistor

“…Silicon nano structures with high aspect ratio have recently attracted extensive attention due to their excellent optical properties . For photoelectric devices such as photovoltaic devices and photoresistors, enhancements in the incident photon absorption by the semiconductor materials with nanostructure can improve the photoelectric energy conversion efficiency and device sensitivity .…”

Porous anodic alumina with low refractive index for broadband graded-index antireflection coatings

“…Different methods of making graded-index AR coatings have been reported, including lithography and wet etching [3], sol-gel process [4], integrated nanoisland coating arrays on nano-conical-frustum arrays [5], improved metal-induced chemical etching [6], and oblique-angle deposition [7,8]. At present, the lowest refractive index n 1.05 was reported by Xi and Schubert et al [7] using oblique-angle deposition, and their study showed that oblique-angle deposition has good control over the refractive index profile when the substrates are flat.…”

Ultra‐High Optical Transparency of Robust, Graded‐Index, and Anti‐Fogging Silica Coating Derived from Si‐Containing Block Copolymers

“…Thus, an effective antirefl ection coating (ARC) for a higher optical transmittance can contribute to the accomplishment of improved contrast and brightness in display devices and higher levels of energy conversion effi ciency in solar panels. [2][3][4][5][6] Various methods, such as lithography, obliqueangle deposition, catalytic etching, chemical vapor deposition, and a sol-gel process, have been reported. An ideal ARC should satisfy the requirements of a quarter-wavelength fi lm thickness and a fi lm η of ( η s ) 0.5 , where η s denotes the η of the substrate.…”

“…Traditional ARCs improve optical transmittance by introducing destructive interference between refl ected light beams from the air-fi lm and fi lm-substrate interfaces. [2][3][4][5] However, these methods may lack cost-effectiveness and high-throughput capabilities due to the requirements of vacuum processing, multiple etching steps, or because of the limited controllability of η .Recently, highly porous block copolymer (BCP) thin fi lms were applied to the fabrication of ARC due to the excellent low-cost solution processability and facile tunability of η when controlling the fraction of the pores generated by the selective removal of one block. [ 1 ] However, an ARC with a homogeneous η can achieve high transmittance only in narrow wavelength and incidence angle ranges, which are fi xed by its thickness and refractive index.…”

“…As a result, the Fresnel refl ection can be effectively minimized in a wide wavelength range and high optical transparency can be achieved. [2][3][4][5] However, these methods may lack cost-effectiveness and high-throughput capabilities due to the requirements of vacuum processing, multiple etching steps, or because of the limited controllability of η . Theoretical studies showed that a quintic profi le of η varying from that of the substrate (typically 1.5-2) to 1 is best for achieving the lowest refl ectance (<0.1% in the visible range).…”