_Article_  
**Atomic Layer Deposition TiO\({}_{2}\) Films and TiO\({}_{2}\)/SiN\({}_{x}\) Stacks Applied for Silicon Solar Cells**  
**[PERSON] 1, [PERSON] 2, [PERSON] 2 and [PERSON] 3,* 1**  
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passivation, but also can serve as anti-reflection coating layers to lower the reflectivity of solar cells, such as Al\({}_{2}\)O\({}_{3}\)/TiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\)/ZnS, Al\({}_{2}\)O\({}_{3}\)/HfO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\)/SiN\({}_{x}\) stacks [9; 10; 11]. Recently, the concept of passivating contact was proposed to further increase the conversion efficiency of c-Si solar cells by using these dielectric materials. Carrier selection and integration of tunneling contacts have been developed to reduce the recombination losses between the photoactive part of the solar cell and the metal contacts. The ultrathin dielectric layers for conductive silicon surface passivation layers can be fabricated easily by the ALD technique [12; 13; 14]. Titanium oxide (TiO\({}_{2}\)) film has been used in the photovoltaic industry as an anti-reflection coating since the 1980s due to its low growth temperature, nontoxic liquid precursors, excellent chemical resistance, optimal reflective index, and low absorbance at wavelengths of the solar spectrum (except the ultraviolet region) [15; 16]. However, stoichiometric TiO\({}_{2}\) films afford little surface passivation on bare silicon wafer [17]. [PERSON] et al. reported that nonstoichiometric titanium oxide films deposited by pulsed laser deposition had a certain degree of passivation for the non-diffused \(p\)-type Si surface [18]. [PERSON] et al. proposed that the TiO\({}_{2}\) thin films deposited by atmospheric pressure chemical vapor deposition (APCVD) could effectively passivate \(n\)-type Si and boron-diffused surfaces. These films were also annealed at 300 \({}^{\circ}\)C in nitrogen (N\({}_{2}\)) ambient and subjected to light soaking by a halogen lamp to create negative charges for further improving the performance of surface passivation [19; 20]. Si surface passivation by TiO\({}_{2}\) thin films using the ALD technique was first reported in 2013 by [PERSON] et al. [21]. In the study, 66-nm-thick TiO\({}_{2}\) films were deposited by ALD on the float-zone (FZ) Si wafers at different substrate temperatures (200 \({}^{\circ}\)C, 300 \({}^{\circ}\)C, 400 \({}^{\circ}\)C and 500 \({}^{\circ}\)C). The results showed that a certain degree of Si surface passivation was observed for relatively lower deposition temperature of TiO\({}_{2}\) films. Recently, [PERSON] et al. reported excellent c-Si surface passivation by atomic layer-deposited amorphous TiO\({}_{2}\) films at even lower temperature (100 \({}^{\circ}\)C) and realized ultralow effective surface recombination velocities down to 2.8 cm/s and 8.3 cm/s for \(n\)-type and \(p\)-type FZ c-Si wafers, respectively [22]. They also demonstrated the excellent performance of passivation for the TiO\({}_{2}\) films on boron-doped industrial Si emitters, which further proved the feasibility of applying TiO\({}_{2}\) film in surface passivation for high efficiency \(n\)-type Si solar cells in the future [23]. In addition, [PERSON] et al. reported that the TiO\({}_{2}\)/Si heterojunction structure can selectively block the transport of holes from Si to the TiO\({}_{2}\) layer [24]. [PERSON] et al. proposed ultrathin amorphous TiO\({}_{2}\) film as the carrier-selective contact layer in \(n\)-type Si solar cells and demonstrated the high conversion efficiency of Si solar cells with a simplified process [25; 26]. Although many research groups demonstrated that TiO\({}_{2}\) films by ALD perform good surface passivation for Si solar cells [27], the characterization of those TiO\({}_{2}\) films is rarely reported in order to understand the mechanisms of Si surface passivation of TiO\({}_{2}\) films (chemical passivation and field-effect passivation).