6 research outputs found
Isolating the photovoltaic junction: atomic layer deposited TiO2-RuO2 alloy Schottky contacts for silicon photoanodes
We synthesized nanoscale TiO2-RuO2 alloys by atomic layer deposition (ALD) that possess a high work function and are highly conductive. As such, they function as good Schottky contacts to extract photogenerated holes from n-type silicon while simultaneously interfacing with water oxidation catalysts. The ratio of TiO2 to RuO2 can be precisely controlled by the number of ALD cycles for each precursor. Increasing the composition above 16% Ru sets the electronic conductivity and the metal work function. No significant Ohmic loss for hole transport is measured as film thickness increases from 3 to 45 nm for alloy compositions >= 16% Ru. Silicon photoanodes with a 2 nm SiO2 layer that are coated by these alloy Schottky contacts having compositions in the range of 13-46% Ru exhibit average photovoltages of 525 mV, with a maximum photovoltage of 570 mV achieved. Depositing TiO2-RuO2 alloys on nSi sets a high effective work function for the Schottky junction with the semiconductor substrate, thus generating a large photovoltage that is isolated from the properties of an overlying oxygen evolution catalyst or protection layer
Collective investments for pension savings: Lessons from Singapore's central provident fund scheme
opinions are solely those of the authors who acknowledge research support from the Wharton-SM
Isolating the Photovoltaic Junction: Atomic Layer Deposited TiO<sub>2</sub>–RuO<sub>2</sub> Alloy Schottky Contacts for Silicon Photoanodes
We synthesized nanoscale TiO<sub>2</sub>–RuO<sub>2</sub> alloys by atomic layer deposition
(ALD) that possess a high work
function and are highly conductive. As such, they function as good
Schottky contacts to extract photogenerated holes from n-type silicon
while simultaneously interfacing with water oxidation catalysts. The
ratio of TiO<sub>2</sub> to RuO<sub>2</sub> can be precisely controlled
by the number of ALD cycles for each precursor. Increasing the composition
above 16% Ru sets the electronic conductivity and the metal work function.
No significant Ohmic loss for hole transport is measured as film thickness
increases from 3 to 45 nm for alloy compositions ≥ 16% Ru.
Silicon photoanodes with a 2 nm SiO<sub>2</sub> layer that are coated
by these alloy Schottky contacts having compositions in the range
of 13–46% Ru exhibit average photovoltages of 525 mV, with
a maximum photovoltage of 570 mV achieved. Depositing TiO<sub>2</sub>–RuO<sub>2</sub> alloys on nSi sets a high effective work
function for the Schottky junction with the semiconductor substrate,
thus generating a large photovoltage that is isolated from the properties
of an overlying oxygen evolution catalyst or protection layer
Titanium Oxide Crystallization and Interface Defect Passivation for High Performance Insulator-Protected Schottky Junction MIS Photoanodes
Atomic layer deposited
(ALD) TiO<sub>2</sub> protection layers
may allow for the development of both highly efficient and stable
photoanodes for solar fuel synthesis; however, the very different
conductivities and photovoltages reported for TiO<sub>2</sub>-protected
silicon anodes prepared using similar ALD conditions indicate that
mechanisms that set these key properties are, as yet, poorly understood.
In this report, we study hydrogen-containing annealing treatments
and find that postcatalyst-deposition anneals at intermediate temperatures
reproducibly yield decreased oxide/silicon interface trap densities
and high photovoltage. A previously reported insulator thickness-dependent
photovoltage loss in metal–insulator–semiconductor Schottky
junction photoanodes is suppressed. This occurs simultaneously with
TiO<sub>2</sub> crystallization and an increase in its dielectric
constant. At small insulator thickness, a record for a Schottky junction
photoanode of 623 mV photovoltage is achieved, yielding a photocurrent
turn-on at 0.92 V vs NHE or −0.303 V with respect to the thermodynamic
potential for water oxidation