Water contact angles (WCAs) were measured on a homemade instrument
equipped with a Charge-Coupled Device (CCD) at room
temperature. The droplet used was 1.5 μL. The WCA was the average
value of five measurements on different locations. The wetting process
was monitored by CCD at 25 frames per second. The antifogging
behavior of silica film was assessed by holding the half-coated glass
slide on the top of a beaker containing hot water. Another method
was to cool the half-coated glass slide in refrigerator at −22 °C for
20 min and then put the slide in humid air (relative humidity: 60%).
The microstructure of the film was observed by field emission scanning
electron microscopy (FE-SEM, Hitachi S-4300) operating at
15 kV. The hardness of the film was assessed by Mitsubishi pencils.
Transmittance of the coated and uncoated glass slides was recorded
on a Shimadzu UV-1601 PC spectrophotometer. The power output
of the crystalline silicon solar cell was measured by Solar Module
Tester (Qinhuangdao Boostsolar Photovoltaic Equipment Co., Ltd) by
a standard protocol (IEC61215, IEC904, IEC891, IEC60904).