Study of optical absorbance in porous silicon nanowires for photovoltaic applications

Abstract

Porous silicon nanowires (PSiNWs) layers fabrication was reported. Reflectance spectra were measured as a function of the nanowire length and were inferior to 0.1% and a strong photoluminescence (PL) signal was measured from samples. Models based on cone shape of nanowires located in circular and rectangular bases were used to calculate the reflectance using the Transfert Matrix Formalism (TMF) of PSiNWs layer. The modeling of the reflectance permits to explain this value by taking account into the shape of the nanowires and its porosity. Optical absorbance and transmission were also theoretically studied. The absorbance was superior to that obtained with silicon nanowires and the ultimate efficiency was about equal to 25% for normal incidence angle. These results could be applied to the potential application in low-cost and high efficiency PSiNWs based solar cells.

Aligned Array of Porous Silicon Nanowires for Gas-Sensing Application

“…This kind of porous SiNWs array open new opportunities for potential applications in photocatalysis, lithium ion battery, gas sensor, photovoltaic, etc, due to its unique microstructure. [17][18][19][20] Gas sensors with low operating temperature, excellent dynamic response-recovery characteristics and high selectivity are in great demand for the environmental protection and human health. The porous SiNWs array possessing high surface area and aligned configuration may be open a new door to develop potential applications in gas sensor with excellent response characteristic.…”

Silicon Nanowires with Mesopores: Fabrication and Optical Properties

“…QC substantially requires to have a characteristic size smaller than the Bohr radius of the free excitons of bulky Si (~5 nm), but the Si skeletons were evaluated larger than 5 nm [46]. Fourth, HF removes the oxide layers of n + -mpSiNWs and significantly causes λ PL red shift from ~700 nm to ~800 nm [47], However, Si is intact in HF, so it is indicated by QC that the reddish PL not shift after the HF etching. The removal of oxides does affect…”

“…The electrochemically-induced porosification of n -SiNWs significantly suppresses the vibrations of interfacial Si-O-Si, O-SiH x and SiH x , illustrating that the reddish PL should not be ascribed to hydrogenated amorphous Si, surface hydrides or polymer molecules on the surfaces [3]. It was proposed that surface states are the defects in the oxide layers [47]. XPS detects Si 0 (Si), Si + (Si 2 O), Si 3+ (Si 2 O 3 ) and Si 4+ (SiO 2 ) in n + -mpSiNWs.…”

“…Therefore, the enhanced antireflection with the porosity of n --mpSiNWs (Figure 9b) is more likely attributed to the tapered structures (Figure 9c). Recently, Charrier et al, created n + -mpSiNWs that have not only the tapered profile (Figure 10a), but also the porosity gradually reducing from the top to root portions (Figure 10b) [47]. The gradient-porosity structures give rise to a graded decrease of refraction index from the Si wafer to the air, resulting in specular reflectance less than 0.1% in the UV-visible spectrum at an incident angle of 6° (Figure 10b).…”

Synthesis, optical properties and residual strain effect of GaN nanowires generated via metal-assisted photochemical electroless etching

“…16 A recently developed photoetching system for n-type GaN, in KOH solution containing the strong oxidizing agent potassium peroxydisulphate (K 2 S 2 O 8 ), was studied by Weyher et al 17,18 The development of the metal-assisted electroless etching to synthesise silicon nanowires was well established during the last few years. 19,20 However, a few reports explored the synthesis of GaN NWs using metal-assisted electroless etching, but the etching mechanism was not well established. 21 Furthermore, the optical and mechanical properties of the GaN NWs, generated via the metal-assisted photochemical electroless method, are not well developed.…”