Low-Temperature Synthesis of a TiO₂/Si Heterojunction

Abstract

The classical SiO2/Si interface, which is the basis of integrated circuit technology, is prepared by thermal oxidation followed by high temperature (>800 °C) annealing. Here we show that an interface synthesized between titanium dioxide (TiO2) and hydrogen-terminated silicon (H:Si) is a highly efficient solar cell heterojunction that can be prepared under typical laboratory conditions from a simple organometallic precursor. A thin film of TiO2 is grown on the surface of H:Si through a sequence of vapor deposition of titanium tetra(tert-butoxide) (1) and heating to 100 °C. The TiO2 film serves as a hole-blocking layer in a TiO2/Si heterojunction solar cell. Further heating to 250 °C and then treating with a dilute solution of 1 yields a hole surface recombination velocity of 16 cm/s, which is comparable to the best values reported for the classical SiO2/Si interface. The outstanding performance of this heterojunction is attributed to Si-O-Ti bonding at the TiO2/Si interface, which was probed by angle-resolved X-ray photoelectron spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that Si-H bonds remain even after annealing at 250 °C. The ease and scalability of the synthetic route employed and the quality of the interface it provides suggest that this surface chemistry has the potential to enable fundamentally new, efficient silicon solar cell devices.

MOF‐Derived Bifunctional Iron Oxide and Iron Phosphide Nanoarchitecture Photoelectrode for Neutral Water Splitting

“…However, for PEC to become economically viable, the efficiency and durability of the electrode is still the most challenging task for researchers. [3][4][5][6][7] Tailoring the hierarchical structure, modification of co-catalyst, and doping are also important factors that control the photocatalytic activity. [2] However, the bare Si surface exhibits sluggish kinetics for water splitting and corrodes readily in harsh electrolyte solutions, which requires the Si surface to be covered with another photo-absorber or electrocatalyst.…”

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

“…[8][9][10] Therefore, to achieve effective solar-to-hydrogen (STH) process, all steps stated above should be in very efficient progress, which requires high optical response for the photoanode materials, [11] efficient carrier separation, and surface reaction. [26] As the conduction band (CB) of silicon is more negative than most of the common MO semiconductors (e.g., TiO 2 , [27,28] WO 3 ), [29] silicon can bring better electron reduction kinetics on the counter electrode. However, as intrinsic semiconductor, the PEC performance of pristine MO photoanode is always hindered by the poor carrier mobility, narrow optical-response range, and slow surface water oxidation kinetics.…”

“…[26] As the conduction band (CB) of silicon is more negative than most of the common MO semiconductors (e.g., TiO 2 , [27,28] WO 3 ), [29] silicon can bring better electron reduction kinetics on the counter electrode. Particularly, benefiting from the outstanding visiblelight response performance and carrier mobility within silicon, it has long been regarded as the most suitable material to build the solar energy conversion device.…”

“…However, as intrinsic semiconductor, the PEC performance of pristine MO photoanode is always hindered by the poor carrier mobility, narrow optical-response range, and slow surface water oxidation kinetics. [26] As the conduction band (CB) of silicon is more negative than most of the common MO semiconductors (e.g., TiO 2 , [27,28] WO 3 ), [29] silicon can bring better electron reduction kinetics on the counter electrode. [20][21][22] For instance, via constructing semiconductor heterojunction with matched band position, the separation and transportation of photoinduced carrier can be effectively enhanced (such as Bi 2 MoO 6 /Si, [23] Ag/Fe 2 O 3 , [24] NiFe-LDH/C 3 N 4 [25] heterojunction).…”

Heterophase-structured nanocrystals as superior supports for Ru-based catalysts in selective hydrogenation of benzene

“…Heterophase structures, sometimes called heterojunctions123, have unique physical and chemical properties due to the synergy between various physical properties and overlapping electronic energy levels456. The junctions of heterophase structures are frequently intriguing sites for physical and chemical processes including photocatalysis7891011.…”