We present a novel solution-based synthesis method enabling the morphology variation of Sb2Se3 light absorbers. The morphology of Sb2Se3 films varies from dense particulate planar films to one-dimensional nanowire-stacked films upon modulating the Sb and Se molar ratio in the precursor ink. The effect of morphology and crystallographic orientation on the electrical and consequently the PEC properties of Sb2Se3-based photocathodes is investigated. Sequential deposition of CdS as a buffer layer with TiO2 and Pt enables us to build a favorable band structure. An onset potential of 0.47 V versus a reversible hydrogen electrode (RHE) is observed with 13.5 mA cm–2 at 0 V versus a RHE under air mass 1.5 global illumination in a pH 1 electrolyte. In addition, the surface-modified photocathode stably produces hydrogen with a photocurrent of 11 mA cm–2 at 0 V versus RHE in a neutral electrolyte, thus demonstrating the promising potential of the proposed Sb2Se3 photocathodes as efficient PEC water-splitting devices.
Copper nanowire (CuNW)-network film is a promising alternative to the conventional indium tin oxide (ITO) as a transparent conductor. However, thermal instability and the ease of oxidation hinder the practical applications of CuNW films. We present oxidation-resistive CuNW-based composite electrodes that are highly transparent, conductive and flexible. Lactic acid treatment effectively removes both the organic capping molecule and the surface oxide/hydroxide from the CuNWs, allowing direct contact between the nanowires. This chemical approach enables the fabrication of transparent electrodes with excellent properties (19.8 Ω sq−1 and 88.7% at 550 nm) at room temperature without any atmospheric control. Furthermore, the embedded structure of CuNWs with Al-doped ZnO (AZO) dramatically improves the thermal stability and oxidation resistance of CuNWs. These AZO/CuNW/AZO composite electrodes exhibit high transparency (83.9% at 550 nm) and low sheet resistance (35.9 Ω sq−1), maintaining these properties even with a bending number of 1280 under a bending radius of 2.5 mm. When implemented in a Cu(In1−x,Gax)(S,Se)2 thin-film solar cell, this composite electrode demonstrated substantial potential as a low-cost (Ag-, In-free), high performance transparent electrode, comparable to a conventional sputtered ITO-based solar cell. A highly thermal and oxidation-resistive AZO/Cu nanowire/AZO composite electrode for thin-film solar cells was fabricated at room temperature without any atmospheric control. Our novel transparent composite electrode showed good thermal oxidation stability as well as high conductivity (∼35.9 Ω/sq), transparency (83.9% at 550 nm) and flexibility. Metal nanowire-based materials are promising alternatives to the conventional transparent electrodes found in solar cells and touchscreen displays because they are naturally flexible and stretchable — attributes that can dramatically improve device lifetimes. Current efforts, however, have been hampered by the need for expensive silver nanowires; lower-cost materials, such as copper nanowires, possess an insulating surface oxide film that deteriorates device conductivity. Jooho Moon and co-workers from Yonsei University, South Korea, have now uncovered a surprising way to remove oxides and organic capping molecules from copper nanowires using lactic acid, a biomolecule commonly found in milk. Room temperature lactic acid treatments, followed by washes with organic solvents, yielded transparent copper nanowire networks that feature direct, metal-to-metal contact. Photovoltaic testing revealed these bendable electrodes had excellent conductivity for high-performance solar applications.
Crystal orientation-dependent etching, charge-carrier trapping behaviour, and performance of single-crystal photocathodes are enabled by ammonia solution etching of thermally-oxidised Cu 2 O.
Solar-energy conversion by photoelectrochemical (PEC) devices is driven by the separation and transfer of photogenerated charge carriers. Thus, understanding carrier dynamics in a PEC device is essential to realizing efficient solar-energy conversion. Here, we investigate time-resolved carrier dynamics in emerging low-cost Sb2Se3 nanostructure photocathodes for PEC water splitting. Using terahertz spectroscopy, we observed an initial mobility loss within tens of picoseconds due to carrier localization and attributed the origin of carrier localization to the rich surface of Sb2Se3 nanostructures. In addition, a possible recombination at the interface between Sb2Se3 and the back contact is elucidated by time-resolved photoluminescence analysis. We also demonstrated the dual role of the RuO x co-catalyst in reducing surface recombination and enhancing charge transfer in full devices using intensity-modulated spectroscopy. The relatively low onset potential of the Sb2Se3 photocathode is attributed to the sluggish charge transfer at a low applied bias rather than to fast surface recombination. We believe that our insights on carrier dynamics would be an important step toward achieving highly efficient Sb2Se3 photocathodes.
Solution processing of earth-abundant Cu2ZnSn(S1-x,Sex)4 (CZTSSe) absorber materials is an attractive research area in the economical and large-scale deployment of photovoltaics. Here, a band-gap-graded CZTSSe thin-film solar cell with 7.1% efficiency was developed using non-toxic solvent-based ink without the involvement of complex particle synthesis, highly toxic solvents, or organic additives. Despite the high series resistance due to the presence of a thick Mo(S,Se)x layer and Zn(S,Se) aggregates, a high short-circuit current density (JSC) was generated. In addition, there was no significant difference in open circuit voltages (VOC) between CZTS (0.517 V) and CZTSSe (0.505–0.479 V) cells, despite a significant band gap change from 1.51 eV to 1.24 eV. The high JSC and less loss of VOC are attributed to the effect of band gap grading induced by Se grading in the CZTSSe absorber layer. Our environmentally benign ink approach will enable the realization of low-cost, large-area, high-efficiency thin-film solar cells.
From March 1983 to June 1991 ten cases (twelve ears) underwent middle ear exploration for severe conductive hearing loss. Absence of oval window was found. Vestibulotomy and reconstruction of the ossicular chain were performed. Among patients with horizontal segments of the facial nerve displaced downward over the oval window region, or those after operation the inital gain of the hearing gradually reduced as a result of ablitecation of new fenestra, fenstration operation on the horizontal semicircular canal was performed. Vestibulotomy (10 ears) had resulted in elevated spech reception thresholds of 10-30 dB or more in 7 ears. Four of these patients had initial gain of the hearing reduced after 3 months. Fenestration in four cases resulted in elevated SRT of 20-45 dB. So fenestration is preferred. The authors have also presented their experience in the management of absence of the oval window.
Recent advances in unconventional foldable and stretchable electronics have forged a new field in electronics. However, traditional conducting metal oxides and metal thin films are inappropriate as electrodes for stretchable devices because they are vulnerable to tensile strain as well as bending strain. In this study, we describe the fabrication of annealing-free, copper nanowire (CuNW)-based stretchable electrodes using an inexpensive metal source through a simple and scalable process at low temperature without a vacuum. We also introduce a reversible and extremely stretchable (up to 700% of strain) helical, CuNW-based conducting spring, which has not been previously used for stretchable electrodes. Jooho Moon, Sunho Jeong and colleagues in South Korea have fabricated conducting meshes and extremely stretchable helices from copper nanowires. Metallic nanowires that are randomly entangled with each other in flexible meshes are of interest as electrical conductors for stretchable electronics. The researchers from Yonsei University and the Korea Research Institute of Chemical Technology fabricated nanowires made of copper with a simple and scalable process based on room-temperature chemical synthesis. When the nanowires were deposited on a flexible polymer substrate, the resulting meshes could stretch to up to twice their original size. When shaped as a helix, the nanowires showed an even greater stretchability of up to 700%. Being more cost-efficient than the silver nanowires used previously for similar applications, these copper nanowires hold a great promise for stretchable electronic circuits or in wearable electronics. A highly stretchable CuNW electrode was fabricated on PDMS substrate by the vacuum filtration method. The fundamental stretchability of CuNW films was demonstrated with a newly structured PDMS matrix. Our novel helix-structured CuNW/PDMS electrode showed excellent stretchability at an extremely high strain of 700%, showing a resistance variation of 3.9.
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