This process formed a dispersed silica nanoparticle layer on the Si wafer. Subsequently, a 20-nm-thick silver film was deposited on the wafers with silica nanoparticles using a DC sputtering system. After removing the silica nanoparticles by ultrasonication in deionized
water, Si wafers with a nano-patterned silver film were obtained. The wafer was chemically etched using 4.8 M HF and 0.15M H2O2 at room temperature CHIR98014 chemical structure to form SiNW arrays. The remaining silver film on the bottom of the SiNW arrays was removed by HNO3 wet etching. Finally, the oxide layer existing on the surface of the SiNW array was removed with a HF solution. Details of the SiNW array fabrication process are shown elsewhere . After the fabrication of SiNW arrays, intrinsic amorphous silicon was deposited by PECVD under the same condition as the heterojunction crystalline silicon solar cell in which the fabrication temperature is 210°C and the operating pressure is 0.3 Torr. After the deposition, the SiNW
array was annealed in a forming gas at 200°C, which is the best annealing temperature for the surface passivation of our a-Si:H. On the other hand, Al2O3 was also deposited using Al(CH3)3 Selleckchem AZD2014 and H2O alternately at 200°C by an ALD system. After the deposition, the SiNW arrays were annealed in a forming gas at 400°C. These nanostructures of the prepared SiNW arrays were characterized by field emission selleck kinase inhibitor scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) with JEOL JSM-7001F (JEOL, Tokyo, Japan). The structure of the interface between SiNW and Al2O3 was observed by transmission electron microscopy (TEM) with HITACHI H-9000NAR (HITACHI, Tokyo, Japan) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with HITACHI HD-2700. Minority carrier lifetime
was measured by the μ-PCD method with KOBELCO LTE-1510EP (KOBELCO, Tokyo Japan). To investigate the carrier lifetime in a SiNW region (τ SiNW), one-dimensional numerical simulations were carried out using PC1D. The electrical transport was calculated by solving Poisson equations and carrier continuity equations. In the simulations, we employed a simple structure in which a homogeneous single-phase material O-methylated flavonoid with a small carrier lifetime is stacked on a crystalline silicon substrate with a large carrier lifetime as shown in Figure 2. The homogeneous single-phase material is equivalent to the SiNW region. We calculated the effective minority carrier lifetime in the structure (τ whole) as a function of the minority carrier lifetime in the equivalent SiNW region (τ SiNW) to investigate the relationship between τ whole and τ SiNW. τ whole corresponds to the measured effective lifetime (τ eff). Electrical parameters used in our simulations are summarized in Table 1.