Protected Light-Trapping Silicon by a Simple Structuring Process for Sunlight-Assisted Water Splitting

L. Santinacci (1) , M.W. Diouf (1) , M.K.S. Barr (1) , Bruno Fabre (2) , L. Joanny (3, 4) , F. Gouttefangeas (4, 3) , Gabriel Loget (2)

1 CINaM - Centre Interdisciplinaire de Nanoscience de Marseille
2 ISCR - Institut des Sciences Chimiques de Rennes
3 ScanMAT - Synthèse Caractérisation Analyse de la Matière
4 C.M.E.B.A. - Centre de Microscopie Electronique à Balayage et microAnalyse

Macroporous layers are grown onto n-type silicon by successive photoelectrochemical etching in HF containing solution and chemical etching in KOH. This specific latter treatment gives highly antireflective properties of the Si surface. The duration of the chemical etching is optimized to render the surface as absorbent as possible and the morphology of the as-grown layer is characterized by scanning electron microscopy. Further functionalization of such structured Si surface is carried out by atomic layer deposition of a thin conformal and homogenous TiO 2 layer that is crystallized by an annealing at 450°C. This process allows using such surfaces as photoanodes for water oxidation. The 40 nm-thick TiO 2 film acts 2 indeed as an efficient protective layer against the photocorrosion of the porous Si in KOH, enhances its wettability and enlarge the light absorption of the photoelectrode. The macroporous Si has a beneficial effect on water oxidation in 1 M KOH and leads to a considerable negative shift of onset potential of ~400 mV as well as a 50 % increase in photocurrent at 1 V vs SCE.

Keywords: Black silicon; Photo-anodes; Functionalizations; Nano structuration; Photo-electrochemical etching; Structuring process; Porous silicon; Water splitting; Antireflective properties; Titanium dioxide; Semiconducting silicon; Scanning electron microscopy; Silicon; Photoelectrochemical cells; Light absorption; Hydrofluoric acid; Electrochemistry; Electromagnetic wave absorption; Electrochemical etching; Deposition; Atomic layer deposition; Black Silicon; Electrochemical Etching; Atomic Layer Deposition; Nanostructuration; Photoanode; Water Splitting; Photoelectrochemical Cells

Domains: Chemical Sciences

L. Santinacci, M.W. Diouf, M.K.S. Barr, Bruno Fabre, L. Joanny, et al.. Protected Light-Trapping Silicon by a Simple Structuring Process for Sunlight-Assisted Water Splitting. ACS Applied Materials & Interfaces, 2016, 8 (37), pp.24810--24818. ⟨10.1021/acsami.6b07350⟩. ⟨hal-01381130⟩