TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: In the method for bi-layer passivation on the surface of the silicon substrate, the bi-layer passivation is applied to the light receiving side of a high-efficiency back-contact/back-junction crystalline silicon solar cell. The method further comprises cleaning the silicon surface before the formation of the chemical oxide thin film in order to form a clean hydrophobic hydrogen-passivated silicon surface, where the cleaning of the silicon surface utilizes a cleaning solution selected from ammonium hydroxide (NH4OH), hydrogen peroxide (H2O2), hydrochloric acid (HCl) followed by removal of the native oxide and hydrogen passivating the surface by a diluted hydrofluoric acid (HF) solution. The thin chemical oxide layer has a thickness in the range of 0.3-5 nm and is formed in a nitric acid (HNO3) aqueous solution at a temperature in the range of 20-80 degrees C. The deposition of the hydrogenated amorphous silicon nitride thin film is performed in an in-line or batch/cluster tool utilizing one of the following processes: plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), atmospheric chemical-vapor deposition (APCVD), or physical vapor deposition (PVD). The deposition of the hydrogenated amorphous silicon nitride thin film comprises a first layer with a higher index of refraction and higher relative silicon-to-nitrogen ratio and a second layer with a lower index of refraction and lower silicon-to-nitrogen ratio. The deposition of the hydrogenated amorphous silicon nitride thin film further comprises positioning the silicon substrate into a plasma enhanced chemical vapor deposition (PECVD) chamber and depositing an amorphous silicon nitride film having a thickness in the range of 10-200 nm at temperatures in the range of 100C-500 degrees C utilizing at least one silicon-containing gas selected from silicon tetrahydride (SiH4), silicon hydride (Si2H6), or metal-organic silicon sources, and at least one nitrogen and hydrogen containing gas selected from ammonia (NH3), H2, and N2 gas precursors, and the silicon nitride deposition conditions are tuned to obtain a refractive index between 1.85 and 2.3. The silicon nitride thin film comprises a stack of at least two silicon nitride films with two different refractive indices, the layer with the higher refractive index positioned closer to the silicon substrate and the layer with the lower refractive index positioned farther from the silicon substrate. The hydrogenated amorphous silicon nitride film has a thickness in the range of 10-200 nm, the deposition parameters such as temperature, gas flows of SiH4, Si2H6, NH3, H2, and N2, chamber pressure, and plasma power are optimized to provide for a relatively high Si-H bond density for improved surface passivation, and the refractive index is maintained between 1.85-2.2 for an antireflection coating with minimal light absorption at all wavelengths 300-1600 cm-1. The step of annealing the silicon substrate further comprises annealing the silicon substrate in a vacuum, or N2, H2, NH3, or forming gas (N2+H2) ambient for 1-120 minutes at or above the temperature of deposition of amorphous silicon nitride thin film. Alternatively, the method for bi-layer passivation on the surface of the silicon substrate comprises: cleaning the surface of the silicon substrate to remove native oxides and other metallic and organic surface contaminants; depositing a hydrogenated amorphous silicon thin film at a temperature substantially in the range of 100-500 degrees C on the surface of the silicon substrate; depositing a hydrogenated amorphous silicon nitride thin film at a temperature substantially in the range of 100-500 degrees C on the hydrogenated amorphous silicon thin film; and annealing the silicon substrate at a temperature substantially in the range of 100-500 degrees C. The hydrogenated amorphous silicon thin film is selected from amorphous silicon (a-Si), amorphous silicon containing oxygen and/or carbon (a-SiOC) or amorphous silicon containing oxygen and/or nitrogen (a-SiON). The bi-layer passivation is applied to the front-side light receiving side of a high-efficiency back-contact/back-junction crystalline silicon solar cell. Preferred Substrate: In the surface-passivated crystalline silicon solar cell substrate, the passivated bi-layer thin film comprises a first layer of chemical oxide having a thickness in the range of 0.5-5 nm and a second layer of silicon nitride positioned on the first layer and having a thickness in the range of 10-200 nm. Preferred Solar Cell: In the high-efficiency back-contact, back-junction thin monocrystalline silicon solar cell, the thinner bottom layer is hydrogenated amorphous sub-stoichiometric silicon oxide, silicon nitride, silicon oxynitride, or silicon carbide with a thickness in the range of 1-10 nm.