Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

Abstract

Titanium oxide (TiO 2 ) films and TiO 2 /SiN x stacks have potential in surface passivation, anti-reflection coatings and carrier-selective contact layers for crystalline Si solar cells. A Si wafer, deposited with 8-nm-thick TiO 2 film by atomic layer deposition, has a surface recombination velocity as low as 14.93 cm/s at the injection level of 1.0 × 10 15 cm −3 . However, the performance of silicon surface passivation of the deposited TiO 2 film declines as its thickness increases, probably because of the stress effects, phase transformation, atomic hydrogen and thermal stability of amorphous TiO 2 films. For the characterization of 66-nm-thick TiO 2 film, the results of transmission electron microscopy show that the anatase TiO 2 crystallinity forms close to the surface of the Si. Secondary ion mass spectrometry shows the atomic hydrogen at the interface of TiO 2 and Si which serves for chemical passivation. The crystal size of anatase TiO 2 and the homogeneity of TiO 2 film can be deduced by the measurements of Raman spectroscopy and spectroscopic ellipsometry, respectively. For the passivating contacts of solar cells, in addition, a stack composed of 8-nm-thick TiO 2 film and a plasma-enhanced chemical-vapor-deposited 72-nm-thick SiN x layer has been investigated. From the results of the measurement of the reflectivity and effective carrier lifetime, TiO 2 /SiN x stacks on Si wafers perform with low reflectivity and some degree of surface passivation for the Si wafer.

Substrate-insensitive atomic layer deposition of plasmonic titanium nitride films

“…ALD of TiN films was carried out using a homemade system described elsewhere [15,16]. We use titanium tetrachloride (TiCl 4 ) and ammonia (NH 3 ) as precursors and argon (Ar) as purging gas, with a gas flow rate of 32 sccm for NH 3 , 40 sccm for Ar, and the flow rate of TiCl 4 is controlled by the deposition temperature (here 25 °C).…”

Highly efficient GeSe micro-air-brick-based thin film standalone solar water-splitting photoelectrode with solar-light-soaking accumulation process

“…TiO 2 fully passivates the GeSe MAB surface, and the conformal coverage does not change the inherent morphology of the GeSe MABs. More interestingly, a TiO 2 layer prepared by the atomic layer deposition method has been reported as an anti-reflection thin film, 63 which means that the TiO 2 coverage adopted on the GeSe MABs would further reduce the surface light reflectance, enhance light absorptivity and promote light-to-heat performance. Therefore, in this work, ALD-TiO 2 was chosen not only to accelerate the separation rate of the photoexcited carriers but also to decrease the surface incident light reflectance of the GeSe MABs.…”

Fresnel calculations of double/multi-layer antireflection coatings on silicon substrates

“…Minimum of spectra shifts to the higher wavelengths as the thickness of SLARC increases. Experimental measurement of TiO2/SiNx DLARC was performed in a polished p-type FZ Silicon wafer and deposited using PECVD at a substrate temperature of 200ºC [32]. MgF2/ZnS DLARC was deposited using electron beam with a substrate temperature of 125ºC for ZnS and 200ºC for MgF2 [33].…”