Shunt Paths Research Articles

Transesophageal echocardiography guidance for percutaneous closure of PFO and a new method to improve the diagnosis and safety during the procedures.

Percutaneous patent foramen ovale (PFO) closure is becoming more and more common for the treatment or prevention of PFO-associated right-to-left shunt (RLS). This study aims to investigate the value of transesophageal echocardiography (TEE) in percutaneous PFO closure, and to explore a new method that can improve intraoperative diagnosis and surgical safety. Based on our inclusion and exclusion criteria, we enrolled 73 patients between 16 and 70 years old (average age 43.25 ± 14.87 years) who underwent percutaneous PFO closure at the Department of Cardiac Surgery, Zhongshan Hospital (Xiamen), Fudan University, from January 2022 to December 2023. Out of the 73 enrolled patients, there were 28 males (38.36%) and 45 females (61.64%), 29 migraine patients (39.73%), 14 patients (19.19%) with headache and dizziness, 14 patients (19.18%) with a history of cerebral infarction (CI), and 25 patients (34.25%) with CI, lacunar infarction or ischemic focus on magnetic resonance imaging (MRI). All patients received routine transthoracic echocardiography (TTE) and agitated saline contrast echocardiography (ASCE) before operations. Percutaneous closure of PFO was completed under the guidance of TEE. In 12 patients, the method of "injection of heparinized sterile saline through the delivery sheath" was used to observe their RLS, and the anatomical characteristics of the PFO according to the shunt path were monitored and evaluated. This method was also applied to some patients to guide the conveyor to pass through the foramen ovale (FO) channel safely and effectively, thereby improving the success rate of PFO closure. The application of TEE during the procedure of percutaneous PFO closure, including preoperative evaluation, intraoperative guidance, and postoperative reevaluation, can offer further details about the anatomical and shunt characteristics of PFO, improve the diagnosis rate, and confirm the safety of the surgical path. It ensures the safety and reliability of the whole operation, greatly improving the success rate and reducing postoperative complications. TEE guidance of percutaneous PFO closure has the advantages of minimal trauma, no radiation and real-time visualization, while injecting heparinized sterile saline through the delivery sheath is safer and more effective in improving the success rate and reducing postoperative complications.

Mixed etching-oxidation process to enhance the performance of spin-transfer torque MRAM for high-performance computing

Spin-transfer torque magnetic random access memory (MRAM) devices have considerable potential for high-performance computing applications; however, progress in this field has been hindered by difficulties in etching the magnetic tunnel junction (MTJ). One notable issue is electrical shorting caused by the accumulation of etching by-products on MTJ surfaces. Attempts to resolve these issues led to the development of step-MTJs, in which etching does not proceed beyond the MgO barrier; however, the resulting devices suffer from poor scalability and unpredictable shunting paths due to asymmetric electrode structures. This paper outlines the fabrication of pillar-shaped MTJs via a four-step etching process involving reactive-ion etching, ion-beam etching, oxygen exposure, and ion-trimming. The respective steps can be cross-tuned to optimize the shape of the pillars, prevent sidewall redeposition, and remove undesired shunting paths in order to enhance MTJ performance. In experiments, the proposed pillar-MTJs outperformed step-MTJs in key metrics, including tunneling magnetoresistance, coercivity, and switching efficiency. The proposed pillar-MTJs also enable the fabrication of MRAM cells with smaller cell sizes than spin–orbit torque devices and require no external field differing from voltage-controlled magnetic anisotropy devices.

Investigation on MOS shunt LVTSCR for ESD application

Continuously scaling down ICs result in more stringent electrostatic discharge (ESD) protection design requirements. Compared with other devices, silicon-controlled rectifier (SCR) has become the first choice for its area efficiency and robustness. In order to improve the latch-up issue of SCR, various schemes have been proposed. A simple method is to extend the SCR path length, which will result in the enlarged ON resistance. Segment technology is also used to improve the holding voltage of SCR, but it will shrink the effective emitter area and lead to the serious degradation of ESD robustness. MS-LVTSCR is used to protect CMOS input ports. The circuit operating voltage is 3.3V and the gate oxide DC breakdown voltage is 19V so that considering the safety margin, the ESD window is from 3.63V to 17.1V. This work proposes a novel MOS shunt low-voltage trigger silicon-controlled rectifier (MS-LVTSCR) electrostatic discharge protection device by inserting an embedded PMOS structure. Compared with the conventional LVTSCR, the proposed MS-LVTSCR achieves 53% improvement in the holding voltage and still maintains high ESD robustness with a current level of 31.5 mA/μm without more device area consumption. In addition, both the TCAD simulation and theoretical analysis were carried out to explore the principle of current shunt effect to improve holding voltage. The extra shunt paths will weaken the conductance modulation effect of the main drift region in the main SCR path and its holding voltage can be further raised by reducing the proportion of main drift region current in the total current. We also conducted detailed studies on the mechanisms and geometry effects of this newly proposed structure via experimental validations.

Improved photovoltaic performance and stability of perovskite solar cells by adoption of an n-type zwitterionic cathode interlayer.

Recently, inverted perovskite solar cells (PeSCs) have witnessed significant advancements; however, their long-term stability remains a challenge because of the oxidation of silver cathodes to form AgI by mobile iodides. To overcome this problem, we propose the integration of an electron-deficient naphthalene diimide-based zwitterion (NDI-ZI) as the cathode interlayer. Compared to the physical ion-blocking layer, it effectively captures ions by forming ionic bonds via electrostatic Coulombic interaction to suppress the migration of iodide and Ag ions. The NDI-ZI interlayer also suppresses the shunt paths and modulates the work function of the Ag electrode by forming interface dipoles, thereby enhancing charge extraction. FA0.85Cs0.15PbI3 based PeSCs incorporating NDI-ZI exhibited a noticeably high power conversion efficiency of up to 23.3% and outstanding stability, maintaining ∼80% of their initial performance over 1500 h at 85 °C and over 500 h under continuous 1-sun illumination. This study highlights the potential of a zwitterionic cathode interlayer in diverse perovskite optoelectronic devices, leading to their improved efficiency and stability.

A Surge Absorber for the Sri Lankan Distribution Substation to Mitigate Lightning Damage

Due to high grounding resistance and soil conditions surge arrester performance decreases. Even though in installation the standard earthing resistance is achieved with time the earthing resistance would be at a high value. When a high voltage arrives at the surge arrestor it discharges the excess voltage by providing low impedance shunt path to ground and providing protection for the transformer. Because of high impedance path the voltage would not divert to the ground and carry on its original path and damage the transformer. Therefore, for areas with high earthing resistances protection must be improved for distribution substations. Throughout this research method of reducing the peak and the rate of rise of surge was analyzed for providing extra protection for the transformer. The selected substation was AV047 it was selected because of lightning occurrence in the selected area, Replacement of the transformer due to damages cause by overvoltage surges and high earthing resistance of the installed substation. Usage of the surge absorber for additional protection was investigated throughout the research. By this method proposed by the research group it was able to provide the sufficient protection for the transformer during surge conditions and reduce the peak and the rate of rise of the surge. Losses of the surge absorber were also analyzed at different conditions. Further an algorithm was developed so that the surge absorber could be implemented to any MV and HV networks for protection of the transformer.

Overcoming Two Key Challenges in Monolithic Perovskite‐Silicon Tandem Solar Cell Development: Wide Bandgap and Textured Substrate—A Comprehensive Review

Abstract33.7% of power conversion efficiency (PCE) in monolithic perovskite‐silicon tandem solar cells (PSTSCs) is an eye‐catcher. Still, the issues emerging from their two main requirements, wide band gap (WBG) perovskites and textured substrates, trigger phase segregation, voltage deficit, perovskite strain, high recombination rates, shunt paths, etc. In addition, the ill‐defined relations of most of these issues to the WBG perovskites and silicon texture originating from the conflicting research outcomes have become severe impediments to developing PSTSCs. From this perspective, an overview of the recently developed monolithic PSTSCs discussing the major hurdles in their up‐scaling, stabilities, and commercialization is presented.

Accelerated constant current stress on triple cation perovskite solar cells

The increasing demand for renewable and cost-effective energy sources requires not only the development of alternative solar technologies, but these new technologies must be stable enough to be used in a real-life application. For this reason, perovskite solar cells (PSCs) must be investigated not only in terms of power conversion efficiency, but also in terms of reliability. In this work, accelerated forward current stress is applied as a tool to investigate PSCs stability and degradation kinetic emulating real-life scenarios. The choice of the hole-blocking layer (HBL) plays a crucial role in PSCs intrinsic instability as well as in their degradation rate, which follows a stretched exponential law. Here, tin oxide (SnOX) and bathocuproine (BCP) are investigated as HBLs observing that for low stress currents BCP-based PSCs degrade faster than SnOX-based PSCs, whereas for large stress currents SnOX-based PSCs degrade faster than BCP-based PSCs. The results also indicated that the major cause of degradation in the devices is primarily driven by the formation of shunt paths leading to cell breakdown. Our findings offer valuable insights for improving the stability of PSCs under accelerated stress conditions and provide useful information for the design of PSC-based solar panels depending on their field of applications.

Changes in ohmic shunts in Cu(In,Ga)Se2 devices during damp heat

To increase the bankability of photovoltaics (PV), a more accurate prediction of the lifetime and degradation-rate of PV modules is required. In past studies, average degradation rates for different technologies have been derived from field data. However, in Cu(In,Ga)Se2 (CIGS) based PV, localized shunts are commonly found in modules coming out of the factory. Although the impact of such localized defects on initial module performance has been studied in the past, their evolution and impact on module performance upon aging remain mostly unknown. In this paper, it is demonstrated that exposure of CIGS devices to elevated temperatures and humidity can result in the partial or complete recovery of localized ohmic shunts. This was observed for three types of shunting defects, each on a different CIGS device characterized before and after damp heat exposure. In each device, the reduction in shunting after damp heat could be observed in illuminated lock-in thermography, photoluminescence and current-voltage measurements. For two of the devices, the positive effect of shunt reduction was counteracted by other degradation mechanisms, such as increase in series resistance of TCO or back contact, while a 4% absolute efficiency increase was observed in the third device. Our data suggests that the shunting is mainly reduced due to oxidation of the materials initially forming the shunting path. The combined effects of moisture degradation and shunt reduction may limit detectability of moisture ingress in electrical performance data. These results illustrate the added value of regular visual inspection and luminescence in quality control.

Do the stent blind insertion into the main portal vein (MPV) and stent diameter influence the surgical outcome of the transjugular intrahepatic portosystemic shunt (TIPS)?

Transjugular intrahepatic portosystemic shunt (TIPS) surgery is a clinical intervention to treat portal hypertension (PH) by deploying a covered stent to establish a shunt path for the portal vein (PV) system, and proper surgical strategy is of great importance to balance the shunt effect and the risk of complications. To understand the clinical strategies of the stent blind insertion and stent selection in clinic, this study investigated the effects of varying stent insertion positions and diameters on the PV hemodynamics and the shunt effect by computational fluid dynamics (CFD) analysis of five post-TIPS subjects. The results showed that the successful TIPS surgeries of the five PH subjects were confirmed by quantifying their pressure drops. The stent insertion positions at the main portal vein (MPV) slightly affected the clinically concerned hemodynamic indexes (i.e., MPV pressure, stent-outlet velocity) and the shunt index (SI). This indicated that the position of the stent going into the MPV may not need to be deliberately selected. Moreover, the covered stents with 6 mm and 8 mm diameters slightly influenced the hemodynamics as well, but the large-diameter stent better improved the shunt effect compared to the small-diameter one. Despite this, the 6 mm stent was suggested thanks to the higher risk of the hepatic encephalopathy (HE) observed in clinic, which indicated the excessive shunt of the 8 mm stent. The current work revealed the effects of different TIPS strategies on the surgical outcome, and could be useful for potential clinical practices.

Eliminating cracking morphology of solution-processed CZTSSe absorbers by Sn-rich composition engineering

Sol-gel method has attracted widespread attention for fabricating highly efficient Cu2ZnSn(S, Se)4 (CZTSSe) solar cells. However, the volume shrinkage of the gel during the baking process will cause severe cracking of CZTSSe films, which results in shunt paths and significantly deteriorates device performance. Herein, an Sn-rich CZTS precursor is proposed to produce high-quality CZTSSe films, which could relieve the shrinkage forces in CZTS precursor film and compensate for Sn loss of CZTSSe absorbers during selenization process. The effects of Sn content on CZTS precursor compactness and the post-selenization process on the crystallization quality of CZTSSe films are thoroughly investigated. Furthermore, the formation of the MoSe2 interfacial layer and the SnSe2 secondary phase can be regulated efficiently. As a result, the separation and collection of carriers are greatly improved as the depletion region width (Wd) of the CZTSSe solar cell is broadened. And the difference between the activation energy (Ea) and band gap (Eg) has decreased, indicating that the carrier recombination loss caused by the deviated Sn content in CZTSSe films has been effectively reduced. Consequently, the efficiency of the CZTSSe device increased from 7.6% to 9.3% through Sn-rich composition engineering. This study elucidates the role of Sn content in the fabrication of high-quality CZTSSe films and advances the development of ambient air-processed CZTSSe solar cells.

Scale-Dependent Thermomechanical-Forced Noncircular Torsional Vibration of Lipid Supramolecular Nanotubes via Timoshenko–Gere Theory

Dynamic modeling of lipid nanotubes as a drug carrier in the skin layer is important. The displacement fields of lipid nanotubes in the shunt path of the skin layer are considered twisting. The twisting of the lipid nanotube in the skin layer causes the warping of the structure and, as a result, causes normal strain. The normal strain in the strain fields is not considered in the torsional noncircular structures. Therefore, in this study, not only the effect of shear strains but also the effect of normal strain on the torsional vibration of lipid nanotubes are considered based on the Timoshenko–Gere theory for the first time. Also, the temperature can be considered in the modeling due to the normal strain in the torsional of warped structures. Then, the governing equations of the forced torsional vibrations of lipid nanotubes, by considering the general warping function of cross-section, are derived based on the nonlocal strain gradient theory. The governing equation is solved by utilizing the convolution integration, and the dynamic responses of lipid nanotubes in the presence of external nonlinear harmonic moving torque are obtained. In the results, dynamic and frequency responses in the presence of temperature for rectangular and elliptical lipid nanotubes have been analyzed. One of the methods of drug release in nanocarriers is stimulation with ultrasound waves. Therefore, stimulating the lipid nanotubes using ultrasound waves at the obtained frequencies makes it possible to release the drug from the lipid nanotubes. Also, the maximum dynamical response of Timoshenko–Gere torsion is less than typical torsion. Increasing the aspect ratio of cross-section dimensions of lipid nanotubes decreased the maximum dynamical response. Increasing the velocity parameter first increases the dynamical twist and then reduces it. Also, the effects of axial forces and temperature on the maximum dynamical responses and the dynamical twist of the lipid nanotubes are studied. For validation, the obtained results are compared with the results of previous research.

Atomic-layer-deposited TiO2 and SnO2 coupled with CdS as double buffer layers for HTL-free Sb2S3 thin-film solar cells

The application of double buffer layers has been proven to be a beneficial approach for the enhancement of the power conversion efficiency (PCE) of antimony sulfide (Sb2S3) thin-film solar cells (TFSCs). Recently, solution-processed SnO2/CdS, TiO2/CdS, ZnMgO/CdS, and ZnSnO/CdS electron transport layers (ETLs) have been investigated as double buffer layers for Sb2S3 TFSCs. Herein, atomic-layer-deposited (ALD) SnO2 and TiO2 ETLs were applied as a double buffer layer with CdS for Sb2S3 TFSCs. The Sb2S3 absorber was deposited using a facile hydrothermal method. The TFSC devices were fabricated based on FTO/SnO2/CdS/Sb2S3/Au or FTO/TiO2/CdS/Sb2S3/Au structure without hole transport layers (HTLs). Experimental analysis revealed the reduction of the surface roughness of ETLs and decreased unfavorable (hk0) orientation of the Sb2S3 absorber after utilizing double buffer layers. Initially, incomplete nucleation of Sb2S3 was observed on SnO2 and TiO2 ETLs, which resulted in the formation of a shunting path. Conversely, complete nucleation of Sb2S3 was observed on CdS and double buffer layers. The highest PCEs of 3.98% and 4.23% were obtained for SnO2/CdS and TiO2/CdS double-buffer-layer-based cells with improvements exceeding 1% compared with the reference CdS buffer layer. Additionally, improvements in open-circuit voltage (VOC) of the order of ∼25 mV and ∼45 mV were respectively observed for SnO2/CdS (VOC = 0.676 V) and TiO2/CdS (VOC = 0.696 V) double-buffer-layer-based devices compared with the reference CdS buffer layer (VOC = 0.648 V). The enhanced device properties are mainly attributed to the improved charge carrier collection and formation of suitable band offset at the absorber and ETLs interfaces.

A novel approach to utilize Al2O3 and polyolefin encapsulant as an optical and electrical materials to mitigate potential-induced of PV modules

The combination of increasing photovoltaic (PV) installation operating voltages of over 1000 V and the discovery of modern PV technologies requires a thorough examination of the sensitivity to potential-induced degradation (PID). An additional dielectric aluminum oxide (Al2O3) layer was coated on a p-type crystalline silicon solar cell to mitigate the effect of PID by reducing the shunting path. We also investigated the effect of PID in the modules fabricated using the conventionally used ethylene-vinyl acetate (EVA) encapsulant and a newly developed next generation polyolefin elastomer (POE) encapsulant. The test was performed in a closed chamber by applying 1000 V between the electrodes and the Al frame and maintaining the conditions of a temperature 85 °C and a relative humidity of 85% for 96 h. Our results demonstrate that the design of the module structure using a POE encapsulant and a solar cell covered with an Al2O3 dielectric layer exhibited a power drop of only 1.37%, while the power drop observed with the conventionally used structure using EVA and without the Al2O3 dielectric layer on the cell was 7.61%. Therefore, the new design can successfully overcome the loss induced by PID in a PV system.

27.6% Perovskite/c‐Si Tandem Solar Cells Using Industrial Fabricated TOPCon Device

AbstractThe tandem cell structure is the most promising solution for the next generation photovoltaic technology to overcome the single‐junction Shockley–Queisser limit. The fabrication of a perovskite/c‐Si monolithic tandem device has not yet been demonstrated on a c‐Si bottom cell produced from an industrial production line. Here, a c‐Si cell with a tunneling oxide passivating contact (TOPCon) structure produced on a production line as the bottom cell of a tandem device, and a top cell featuring solution‐processed perovskite films to form the tandem device are used. The c‐Si cell features a rough damage etched, but untextured front surface from the wafering processes. To combat the challenge of rough surfaces, several strategies to avoid shunt paths across carrier transport layers, absorber layers, and their interfaces are implemented. Moreover, the origin of reflection loss on this planar structure is investigated and the reflection loss is managed to below 4 mA cm−2. In addition, the source of the voltage loss from the TOPCon bottom cell is identified and the device structure is redesigned to be suitable for tandem applications while still using mass production feasible fabrication methods. Overall, 27.6% efficiency is achieved for a monolithic perovskite/c‐Si tandem device, with significant potential for future improvements.

A New Inductance Cancelation Scheme for Surface Mount Shunt Capacitor Filters

This article describes a new inductance cancelation scheme. The new scheme, named bilateral magnetic coupling (BMC), is applied to a surface mount shunt capacitor filter on a printed circuit board. In the filter structure, input/output paths are placed in parallel with the shunt path from a power supply trace to a ground plane. To reduce parasitic inductance of the shunt path, magnetic couplings between the input/output paths and the shunt path are utilized. The theory of BMC is explained by the method of partial equivalent elements circuit. The filter parameter design of the BMC is investigated using parametric electromagnetic simulation. When BMC performance was evaluated on a test board, it improved by 4.5 dB at 100 MHz under operation of ICs. These results show that the BMC improves the filter performance in the frequency range from a few megahertz to subgigahertz, where noise reduction is important in digital systems.

Suppression of pinhole defects in thin film CdS/CdTe solar cell via gelatin-based negative photoresist passivation

The existence of pinholes at the CdS/CdTe and CdTe/back contact interfaces is one of the main obstacles to achieve high power conversion efficiency (PCE) in thin film CdS/CdTe solar cells, which leads to the formation of shunt paths in the devices. In this paper, a gelatin-based negative photoresist (Gel-NP) is utilized to fill the pinhole defects of CdTe thin film in photovoltaic device with FTO/CdS/CdTe/Mo/Al/Cr structure. The results showed that the pinholes in CdTe thin film have been effectively filled via the passivation of the Gel-NP, and no residue was found on the surface of CdTe thin film, thus increasing the cell shunt resistance. In addition, the optoelectronic performance of CdS/CdTe thin film solar cell under different Cu diffusion concentrations have been investigated with and without Gel-NP treatment, in which Gel-NP passivates the surface of CdTe resulting in a large amount of Cu enriched on the back, forming CuxTe after annealing. As a result, the average PCE of FTO/CdS/CdTe/Mo/Al/Cr structured solar cell increased from 10.4% to 13.7% via Gel-NP passivation (14.1% of champion efficiency), which exhibits improved reproducibility as well.

Comparison of electrical characteristics of Schottky junctions based on CdS nanowires and thin film

CdS nanowires and film Schottky diodes are fabricated and diode properties are compared. Effect of SnO2 on CdS film diode properties is investigated. CdS film/Au on 100 nm SnO2 substrate demonstrates like-resistor characteristics and increase in SnO2 thickness corrects resistor behavior, however the effective reverse saturation current density J o is significantly high and shunt resistance are considerably low, implying that SnO2 slightly prevents impurities migration from CdS films into ITO but cause additional issues. Thickness of CdS film on diode properties is further investigated and increasing CdS film thickness improved J o by one order of magnitude, however shunt resistance is obviously low, suggesting intrinsic issues in CdS film. 100 nm CdS nanowire/Au diodes reduce J o by three orders of magnitude in the dark and two orders of magnitude in the light respectively and their shunt resistance is significantly enhanced by 70 times when comparing with those of the CdS film diodes. The wide difference can be attributed to the fact that CdS nanowires overcome intrinsic issues in CdS film and thus demonstrate significantly well- defined diode behavior. Simulation found that CdS nanowire diodes have low compensating acceptor type traps and interface state density of 5.0 × 109 cm−2, indicating that interface recombination is not a dominated current transport mechanism in the nanowire diodes. CdS film diodes are simulated with acceptor traps and interface state density increased by two order of magnitude and shunt resistance reduced by one order of magnitude, indicating that high density of interface states and shunt paths occur in the CdS film diodes.

Investigating the reliability of electrically conductive adhesives for shingled photovoltaic Si modules

This paper discusses the environmental stability of an electrically conductive adhesive (ECA) applied to shingled photovoltaic (PV) modules. This study aims to verify the degradation behavior of ECA joints when shingled PV modules are exposed to an accelerated aging test under hot and humid environmental conditions. To achieve this, we prepared shingled PV modules through an assembly process wherein five pre-cut crystalline silicon solar cells were bonded with a ECA paste cured by an infrared lamp, and then stored under damp heat (85 °C/85% RH) and high temperature (65 and 85 °C) conditions. To confirm the aging of the ECA, we determined the changes in the electrical resistance of the ECA and in the efficiencies of the shingled PV modules. Results suggest that the electrical properties of the ECA did not deteriorate under heat and moisture conditions, while the performance of the shingled modules degraded under the same conditions. It was confirmed that the degradation in performance was mainly due to a drop in the fill factor (FF) caused by current leakage. Physicochemical analyses of the samples revealed that Ag atoms, which diffused from the ECA joint to the Si wafer, acted as the shunt path for the solar cell. The bonding properties of the ECA joint to moisture were evaluated as well.

Impact of target power on the properties of sputtered intrinsic zinc oxide (i-ZnO) thin films and its thickness dependence performance on CISe solar cells

Highly resistive intrinsic zinc oxide (i-ZnO) thin films were deposited via radio frequency (RF) magnetron sputtering with varying the target power (80 W–140 W) at constant sputtering gas pressure (10 mTorr), and the structural, morphological, and optical properties were investigated. The i-ZnO thin film crystallized in Wurtzite hexagonal with a preferential orientation along (002) reflection plane. The variation in morphology from partitioned nano-walls to spherical grains pursued the impact of target power on the growth mechanism of i-ZnO thin films. The optical band gap was increased from 3.16 eV (80 W) to 3.28 eV (120 W) with increasing target power. Additionally, CuInSe 2 (CISe) solar cells were fabricated from modified sequentially evaporated metallic precursors by adopting different thicknesses of i-ZnO ranges from 40 nm to 120 nm. The formation of smooth and densely packed grains pursued the effective intermediate layer for the elemental interdiffusion from adjacent layers and protected against the shunt path. 80 nm was the optimum thickness of the i-ZnO film, which yielded 9.23% of conversion efficiency. A further increase of thickness from 80 nm reduced the photovoltaic performance, especially fill factor and elevated value of series resistance. These results explore experimentally the correlation between the i-ZnO thickness and its photovoltaic performance. • The intrinsic zinc oxide (i-ZnO) thin films were deposited by RF sputtering. • RF power affected the properties of i-ZnO thin films. • Sequentially deposited CISe solar cells were prepared followed by selenization. • 80 nm thick i-ZnO films yielded the best conversion efficiency (9.23%).

Atomistic structure and three-dimensional spatial distribution of oxide clusters along voids in nitride metal/semiconductor superlattices

Epitaxial metal/semiconductor superlattices with atomically sharp interfaces and tunable Schottky barrier heights have attracted significant interest in recent years for thermionic emission-based high-temperature thermoelectric devices, optical hyperbolic metamaterials, hot-electron photocatalysis, and optoelectronic heterostructures for visible-to-terahertz frequency range applications. ZrN/ScN is a demonstration of such epitaxial metal/semiconductor superlattices and exhibits atomically sharp lattice-matched interfaces, albeit with the presence of threading dislocations on MgO substrates. Along with its influence on structural integrity and atomic diffusion, the presence of such defects significantly impacts electron and phonon transport in these metamaterials with carrier trapping, scattering, shunt path, etc. Therefore, an in-depth analysis of the atomistic structure and the composition of such defects is extremely necessary to design devices with improved efficiencies. In this paper, high-resolution scanning transmission electron microscopy and atom-probe tomography are employed to determine the structure and three-dimensional (3D) spatial distribution of oxide defect clusters along the voids in ZrN/ScN superlattices. $\mathrm{Sc}{\mathrm{O}}^{+}$ and $\mathrm{Sc}{\mathrm{O}}^{++}$ ions are found to cluster predominantly along such 3D interface defects with zirconium and scandium atoms surrounding them. Defect regions are also found to be depleted of nitrogen atoms and rich with a high concentration of oxygen. The oxygen content was found to be higher inside the ScN layers compared to ZrN. First-principles modeling analysis verified the clustering of oxygen at high oxygen partial pressure and demonstrated a higher affinity of scandium towards oxygen than for zirconium towards oxygen. These results mark significant progress in understanding the atomic structure and composition of defects in nitride superlattices.