@article {1174, title = {Mg $\less$sub$\greater$x$\less$/sub$\greater$ Zn$\less$sub$\greater$1-x $\less$/sub$\greater$O contact to CuGa$\less$sub$\greater$3$\less$/sub$\greater$Se$\less$sub$\greater$5$\less$/sub$\greater$ absorber for photovoltaic and photoelectrochemical devices}, journal = {Journal of Physics: Energy}, volume = {3}, year = {2021}, month = {jan}, pages = {024001}, abstract = {CuGa3Se5 is a promising candidate material with wide band gap for top cells in tandem photovoltaic and photoelectrochemical (PEC) devices. However, traditional CdS contact layers used with other chalcopyrite absorbers are not suitable for CuGa3Se5 due to the higher position of its conduction band (CB) minimum. Mg x Zn1- x O (MZO) is a transparent oxide with adjustable band gap and CB position as a function of magnesium composition, but its direct application is hindered by CuGa3Se5 surface oxidation. Here, MZO is investigated as a contact (n-type {\textquoteleft}buffer{\textquoteright} or {\textquoteleft}window{\textquoteright}) material to CuGa3Se5 absorbers pretreated in Cd2+ solution, and an onset potential close to 1 V vs reversible hydrogen electrode in 10 mM hexaammineruthenium (III) chloride electrolyte is demonstrated. The Cd2+ surface treatment changes the chemical composition and electronic structure of the CuGa3Se5 surface, as demonstrated by photoelectron spectroscopy measurements. The performance of CuGa3Se5 absorber with Cd2+ treated surface in the solid-state test structure depends on the Zn/Mg ratio in the MZO layer. The measured open circuit voltage of 925 mV is promising for tandem PEC water splitting with CuGa3Se5/MZO top cells.}, keywords = {Photocathode; PEC; Buffer layer; CuGaSe; MgZnO}, doi = {10.1088/2515-7655/abd3b3}, url = {https://doi.org/10.1088/2515-7655/abd3b3}, author = {Imran S Khan and Christopher P Muzzillo and Craig L Perkins and Andrew G Norman and James L Young and Nicolas Gaillard and Andriy Zakutayev} } @article {1089, title = {Molybdenum Disulfide Catalytic Coatings via Atomic Layer Deposition for Solar Hydrogen Production from Copper Gallium Diselenide Photocathodes}, journal = {ACS Applied Energy Materials}, volume = {2}, year = {2019}, pages = {1060-1066}, abstract = {

We demonstrate that applying atomic layer deposition-derived molybdenum disulfide (MoS2) catalytic coatings on copper gallium diselenide (CGSe) thin film absorbers can lead to efficient wide band gap photocathodes for photoelectrochemical hydrogen production. We have prepared a device that is free of precious metals, employing a CGSe absorber and a cadmium sulfide (CdS) buffer layer, a titanium dioxide (TiO2) interfacial layer, and a MoS2 catalytic layer. The resulting MoS2/TiO2/CdS/CGSe photocathode exhibits a photocurrent onset of +0.53 V vs RHE and a saturation photocurrent density of -10 mA cm{\textendash}2, with stable operation for \>5 h in acidic electrolyte. Spectroscopic investigations of this device architecture indicate that overlayer degradation occurs inhomogeneously, ultimately exposing the underlying CGSe absorber.

}, doi = {10.1021/acsaem.8b01562}, url = {https://doi.org/10.1021/acsaem.8b01562}, author = {Thomas R. Hellstern and David W. Palm and James Carter and Alex D. DeAngelis and Kimberly Horsley and Lothar Weinhardt and Wanli Yang and Monika Blum and Nicolas Gaillard and Clemens Heske and Thomas F. Jaramillo} } @article {1098, title = {Wide-Bandgap Cu(In,Ga)S2 Photocathodes Integrated on Transparent Conductive F:SnO2 Substrates for Chalcopyrite-Based Water Splitting Tandem Devices}, journal = {ACS Applied Energy Materials}, volume = {2}, year = {2019}, month = {08/2019}, pages = {5515-5524}, abstract = {

Published on August 26th, 2019.

}, issn = {2574-0962, 2574-0962}, doi = {10.1021/acsaem.9b00690}, url = {http://pubs.acs.org/doi/10.1021/acsaem.9b00690}, author = {Nicolas Gaillard and Dixit Prasher and Marina Chong and Alexander Deangelis and Kimberly Horsley and Hope A. Ishii and John P. Bradley and Joel Varley and Tadashi Ogitsu} } @article {798, title = {Low-Cost, Efficient, and Durable H2 Production by Photoelectrochemical Water Splitting with CuGa3Se5 Photocathodes}, journal = {ACS Applied Materials \& Interfaces}, volume = {10}, year = {2018}, note = {

{\textquoteright}doi: 10.1021/acsenergylett.0c01132\n - I.Am.Hydrogen{\textquoteright} {\textquoteright}\n - jyoungstrom{\textquoteright} {\textquoteright}Jason thinks this is great.\n\ \n - jyoungstrom{\textquoteright} {\textquoteright}\n - estechel{\textquoteright}

}, pages = {19573-19579}, abstract = {

Published on June 13th, 2018. Photoelectrochemical (PEC) water splitting is an elegant method of converting sunlight and water into H2 fuel. To be commercially advantageous, PEC devices must become cheaper, more efficient, and much more durable. This work examines low-cost polycrystalline chalcopyrite films, which are successful as photovoltaic absorbers, for application as PEC absorbers. In particular, Cu{\textendash}Ga{\textendash}Se films with wide band gaps can be employed as top cell photocathodes in tandem devices as a realistic route to high efficiencies. In this report, we demonstrate that decreasing Cu/Ga composition from 0.66 to 0.31 in Cu{\textendash}Ga{\textendash}Se films increased the band gap from 1.67 to 1.86 eV and decreased saturated photocurrent density from 18 to 8 mA/cm2 as measured by chopped-light current{\textendash}voltage (CLIV) measurements in a 0.5 M sulfuric acid electrolyte. Buffer and catalyst surface treatments were not applied to the Cu{\textendash}Ga{\textendash}Se films, and they exhibited promising stability, evidenced by unchanged CLIV after 9 months of storage in air. Finally, films with Cu/Ga = 0.36 (approximately stoichiometric CuGa3Se5) and 1.86 eV band gaps had exceptional durability and continuously split water for 17 days (\~{}12 mA/cm2 at -1 V vs RHE). This is equivalent to \~{}17\ 200 C/cm2, which is a world record for any polycrystalline PEC absorber. These results indicate that CuGa3Se5 films are prime candidates for cheaply achieving efficient and durable PEC water splitting.

}, issn = {1944-8244}, doi = {10.1021/acsami.8b01447}, url = {https://doi.org/10.1021/acsami.8b01447}, author = {Christopher P. Muzzillo and W. Ellis Klein and Zhen Li and Alexander Daniel DeAngelis and Kimberly Horsley and Kai Zhu and Nicolas Gaillard} } @article {1092, title = {Wide Band Gap CuGa(S,Se)2 Thin Films on Transparent Conductive Fluorinated Tin Oxide Substrates as Photocathode Candidates for Tandem Water Splitting Devices}, journal = {The Journal of Physical Chemistry C}, volume = {122}, year = {2018}, month = {07/2018}, pages = {14304-14312}, abstract = {

Published on July 5th, 2018. The purpose of this work was to explore the potential of CuGa(S,Se)2 thin films as wide-EG top cell absorbers for photoelectrochemical (PEC) water splitting. A synthesis was developed on fluorinated tin oxide (FTO) photocathodes by converting copper-rich co-evaporated CuGaSe2 into CuGa(S,Se)2 via a post-deposition annealing. We found it necessary to first anneal CuGaSe2 at low-temperature in sulfur then at high-temperature in nitrogen to preserve the transparency and conductivity of the FTO. Using this two-step synthesis, we fabricated a 1.72 eV CuGa(S,Se)2 photocathode with a saturation current density and photocurrent onset potential of 10 mA/cm2 and -0.20 V versus reversible hydrogen electrode, respectively. However we found that the PEC performance and sub-EG transmittance, worsened with increasing copper content. Using flatband potential measurements and the Gerischer model, we show that divergences in PEC performance of CuGa(S,Se)2 photocathodes can be explained by differences in conduction band minimums and Fermi levels. We also explain that sub-EG transmittance is likely hampered by a defect band 100{\textendash}400 meV below EC. Additional external quantum efficiency measurements of a high-efficiency 1.1 eV Cu(In,Ga)Se2 photovoltaic driver, while shaded by the CuGa(S,Se)2 photocathode, yielded a short-circuit current density of 4.14 mA/cm2 revealing that CuGa(S,Se)2 shows promise as a top cell for PEC water splitting.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.8b02915}, url = {https://doi.org/10.1021/acs.jpcc.8b02915}, author = {Alexander D. DeAngelis and Kimberly Horsley and Nicolas Gaillard} }