Enhancement of the open circuit voltage of Cu2O/Ga2O3 heterojunction solar cells through the mitigation of interfacial recombination

Chua, Danny; Kim, Sang Bok; Gordon, Roy G.

doi:10.1063/1.5096283

Cited by 34 publications

(20 citation statements)

References 24 publications

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“…These data suggest that the surface states, and in analogy also interface states, rather than the bulk defects limit the photovoltage in Cu 2 O heterostructures. This is supported by recent observations of very high opencircuit voltages in Cu 2 O/Ga 2 O 3 heterojunction solar cells 12,13 .…”

supporting

confidence: 78%

Influence of surface defect density on the ultrafast hot carrier relaxation and transport in $${\hbox {Cu}}_2 {\hbox {O}}$$ photoelectrodes

Grad

Novotný

Hengsberger

et al. 2020

Sci Rep

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Cuprous oxide (Cu 2 O) is a promising material for photoelectrochemical energy conversion due to its small direct band gap, high absorbance, and its Earth-abundant constituents. High conversion efficiencies require transport of photoexcited charges to the interface without energy loss. We studied the electron dynamics in Cu 2 O(111) by time-resolved two-photon photoemission for different surface defect densities in order to elucidate the influence on charge carrier transport. On the pristine bulk terminated surface, the principal conduction bands could be resolved, and ultrafast, elastic transport of electrons to the surface was observed. On a reconstructed surface the carrier transport is strongly suppressed and defect states dominate the spectra. Evidence for surface oxygen vacancies acting as efficient carrier traps is provided, what is important for further engineering of Cu 2 O based photoelectrodes. The conversion of solar energy into fuel in photoelectrochemical cells (PEC) represents a sustainable way for energy conversion and storage, a typical route being the production of hydrogen via water splitting 1-3. Upon light absorption in some semiconducting electrode material, photoexcited charges are generated that are separated and transported to the solid-electrolyte interface. Here they drive some catalyst-promoted redox chemistry that stores their energy in chemical bonds 4. This concept promises to be both ecologically and economically attractive if electrodes with high conversion efficiencies can be built from cheap, Earth-abundant materials that are stable in the aggressive chemical environment of a PEC cell 5. Cuprous oxide (Cu 2 O) has attracted much attention recently as electrode material for photo-electrochemical water splitting 6-10. It is a p-type semiconductor with a band gap of 2.1 eV and has a maximum theoretical solarto-hydrogen (STH) conversion efficiency of 18% 8. The bare material is unstable towards reduction to metallic Cu under electrochemical hydrogen evolution conditions, but protective nanolayers of n-type TiO 2 or ZnO can stabilize the electrode. The alignment of the conduction bands and the band bending near the p-n junction make for the charge separation and transport of photoexcited electrons to the oxide-electrolyte interface 6. Ga 2 O 3 nanolayers showed an even better band alignment for charge transport due to the very small conduction band offset. Recently a nanostructured photocathode design with Cu 2 O/Ga 2 O 3 /TiO 2 buried junctions and with NiMo as hydrogen evolution catalyst was demonstrated 9. It was implemented conformally in a coaxial nanowire structure to match the light absorption depth to the much shorter minority carrier diffusion length. It combines efficient light absorption with high positive onset voltage and shows high photocurrent density, paving the way towards efficient water splitting devices based entirely on Earth-abundant materials. Electrode performance is very sensitive to the presence of interfacial or bulk defects, which typically form states wit...

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supporting

confidence: 78%

Influence of surface defect density on the ultrafast hot carrier relaxation and transport in $${\hbox {Cu}}_2 {\hbox {O}}$$ photoelectrodes

Grad

Novotný

Hengsberger

et al. 2020

Sci Rep

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“…Of note, this beneficial effect on photovoltage, when coupling Cu 2 O to Ga 2 O 3 to form a heterojunction, was also observed by Chua et al. in their development of an all‐oxide solar cell, which achieved a record high V oc of ≈1.8 V. [ 210 ]…”

Section: Materials Choice For Pec Water Splittingmentioning

confidence: 55%

A Review of Inorganic Photoelectrode Developments and Reactor Scale‐Up Challenges for Solar Hydrogen Production

Moss

Babacan

Kafizas

et al. 2021

Advanced Energy Materials

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Green hydrogen, produced using solar energy, is a promising means of reducing greenhouse gas emissions. Photoelectrochemical (PEC) water splitting devices can produce hydrogen using sunlight and integrate the distinct functions of photovoltaics and electrolyzers in a single device. There is flexibility in the degree of integration between these electrical and chemical energy generating components, and so a plethora of archetypal PEC device designs has emerged. Although some materials have effectively been ruled out for use in commercial PEC devices, many principles of material design and synthesis have been learned. Here, the fundamental requirements of PEC materials, the top performances of the most widely studied inorganic photoelectrode materials, and reactor structures reported for unassisted solar water splitting are revisited. The main phenomena limiting the performance of up‐scaled PEC devices are discussed, showing that engineering must be considered in parallel with material development for the future piloting of PEC water splitting systems. To establish the future commercial viability of this technology, more accurate techno‐economic analyses should be carried out using data from larger scale demonstrations, and hence more durable and efficient PEC systems need to be developed that meet the challenges imposed from both material and engineering perspectives.

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“…[14][15][16] It is quite interesting that the performance of UV PD using a-GaO x is comparable or even better than its crystalline counterpart. [15,17] Except for UV PDs, a-GaO x materials also have extensive applications in areas of solar cells, [18][19][20][21] phosphors, [22,23] resistance random access memories (RRAMs), [24][25][26][27] gas sensors, [28] and radiation detectors. [29] These versatile applications together with the fact that scalable a-GaO x can be easily prepared on almost any substrates make it appealing for flexible electronics and giant microelectronics.…”

Section: Introductionmentioning

confidence: 99%

Recent Progress of Deep Ultraviolet Photodetectors using Amorphous Gallium Oxide Thin Films

Liang

Han

2020

Physica Status Solidi (a)

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Deep ultraviolet (UV) photodetectors have wide applications both in civil and military fields. Many materials have been explored to realize deep UV photodetection. Amorphous gallium oxide (a‐GaOx), as a member of transparent amorphous oxide semiconductors (TAOSs), has attracted a great deal of attention due to its ultrawide bandgap and scalable synthesis at room temperature. Plenty of researches have been focused on this topic in recent years. Herein, the latest progresses in the preparation methods of a‐GaOx using radio‐frequency sputtering, pulsed laser deposition, atomic layer deposition, and other deposition techniques are summarized. Dependence of the stoichiometry, crystallinity, optical, electrical, and morphological properties on different preparation parameters and doping/alloying elements is tentatively discussed, as well as those deep UV photodetectors based on a‐GaOx and related thin films. Finally, a short summary with further possible investigations is provided for a better understanding and development of a‐GaOx materials and photodetectors.

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Enhancement of the open circuit voltage of Cu2O/Ga2O3 heterojunction solar cells through the mitigation of interfacial recombination

Cited by 34 publications

References 24 publications

Influence of surface defect density on the ultrafast hot carrier relaxation and transport in $${\hbox {Cu}}_2 {\hbox {O}}$$ photoelectrodes

Influence of surface defect density on the ultrafast hot carrier relaxation and transport in $${\hbox {Cu}}_2 {\hbox {O}}$$ photoelectrodes

A Review of Inorganic Photoelectrode Developments and Reactor Scale‐Up Challenges for Solar Hydrogen Production

Recent Progress of Deep Ultraviolet Photodetectors using Amorphous Gallium Oxide Thin Films

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