Scaling-Up of Thin-Film Photoelectrodes for Solar Water Splitting Based on Atomic Layer Deposition

Abstract

Atomic layer deposition (ALD) is an established method to prepare protective layers for Si-based photoelectrodes for photoelectrochemical (PEC) water splitting. Although ALD has been widely used in microelectronics and photovoltaics, it remains a great challenge to design simple and effective ALD systems to deposit large and uniform protective films for Si-based photoelectrodes with industrial sizes. This paper describes the design and realization of a simple ALD chamber configuration for photoelectrodes with large sizes, in which the influence of a gas redistributor over the gas flow and heat transfer during film growth was revealed by computational fluid dynamics simulations and experimental investigations. A simple circular baffle-type redistributor was proposed to establish a uniform gas flow field throughout the ALD reactor, resulting in a uniform temperature profile. With this simple baffle redistributor, the large-area Al2O3 monitor film (46 nm thickness) reached a good nonuniformity (Nu %) of 0.88% over a large area of 256 cm2. This design enables the fabrication of large-scale photocathodes from standard industrial-grade 166 mm Si(100) wafers (276 cm2) by depositing 50 nm TiO2 protective films with Nu % less than 5%. The obtained photocathode achieves a saturation current of 6.45 A with a hydrogen production rate of 43.2 mL/min under outdoor illumination. This work elucidates how flow pattern and heat transfer may influence the deposition of protective layers over large photoelectrodes, providing guidance for future industrial applications of PEC water splitting.

Tandem cells for unbiased photoelectrochemical water splitting

“…272 However, the uniformity, components, thickness, and other associated properties of the photoelectrode materials, protective layer and catalyst deposition cannot be guaranteed in mass production. Therefore, it is necessary to develop a large area or batch thin-film deposition techniques, 273 to overcome this dilemma. Moreover, when operating tandem cells at high current densities, mass transfer and pH gradients become significant concerns.…”

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

“…ALD is an established method, by which we have deposited a 50 nm TiO 2 protective layer on industrial-grade 166 mm Si (100) wafers. 58 Another issue is the redesign of the large-size devices, in which the light management, mass transfer, gas separation, etc., need to be carefully considered. Finally, the cost-effectiveness should be another essential factor, which needs a detailed technoeconomic assessment.…”

“…First, it is important to deposit films with controllable properties over a large area. ALD is an established method, by which we have deposited a 50 nm TiO 2 protective layer on industrial-grade 166 mm Si (100) wafers . Another issue is the redesign of the large-size devices, in which the light management, mass transfer, gas separation, etc., need to be carefully considered.…”

Biofuels and hydrogen production: back to the Langmuir–Blodgett approach for large-scale structuration of Bi-based photoelectrodes

“…For the specific applications in photoelectrocatalysis as well as photovoltaics, the dimensions of the support aforementioned for the LB are really typical of the semi or fully-industrial scale as recently seen for the atomic layer deposition technique dealing with photelectrodes of large area (256 cm 2 ) and silicon wafer (166 cm 2 ). 71 Dilger et al 72 also tried to design 40 cm 2 of LaTiO 2 N photoanodes for water splitting by electrophoretic process, followed by a dip coating and thermal treatment. The volume used for all these depositions by LB or other approaches remains under 100 mL and, most of the time, is in the mL or mL range.…”