Design Rule of Electron- and Hole-Selective Contacts for Polycrystalline Silicon-Based Passivating Contact Solar Cells.

A crystalline silicon (c-Si) solar cell with a polycrystalline silicon/SiOx (poly-Si/SiOx) structure, incorporating both electron and hole contacts, is an attractive choice for achieving ideal carrier selectivity and serving as a fundamental component in high-efficiency perovskite/Si tandem and interdigitated back-contact solar cells. However, our understanding of the carrier transport mechanism of hole contacts remains limited owing to insufficient studies dedicated to its investigation. There is also a lack of comparative studies on the poly-Si/SiOx electron and hole contacts for ideal carrier-selective solar cells. Therefore, this study aims to address these knowledge gaps by exploring the relationship among microstructural evolution, dopant in-diffusion, and the resulting carrier transport mechanism in both the electron and hole contacts of poly-Si/SiOx solar cells. Electron (n+ poly-Si/SiOx/substrate)- and hole (p+ poly-Si/SiOx/substrate)-selective passivating contacts are subjected to thermal annealing. Changes in the passivation properties and carrier transport mechanisms of these contacts are investigated during thermal annealing at various temperatures. Notably, the results demonstrate that the passivation properties and carrier transport mechanisms are strongly influenced by the microstructural evolution of the poly-Si/SiOx layer stack and dopant in-diffusion. Furthermore, electron and hole contacts exhibit common behaviors regarding microstructural evolution and dopant in-diffusion. However, the hole contacts exhibit relatively inferior electrical properties overall, mainly because both the SiOx interface and the p+ poly-Si are found to be highly defective. Moreover, boron in the hole contacts diffuses deeper than phosphorus in the electron contacts, resulting in deteriorated carrier collection. The experimental results are also supported by device simulation. Based on these findings, design rules are suggested for both electron and hole contacts, such as using thicker SiOx and/or annealing the solar cell at a temperature not exceeding the critical annealing temperature of the hole contacts.

Thermal annealing effects on tunnel oxide passivated hole contacts for high-efficiency crystalline silicon solar cells.

Tunnel oxide passivated contacts (TOPCon) embedding a thin oxide layer between polysilicon and base crystalline silicon have shown great potential in the development of solar cells with high conversion efficiency. In this study, we investigate the formation mechanism of hole-carrier selective contacts with TOPCon structure on n-type crystalline silicon wafers. We explore the thermal annealing effects on the passivation properties in terms of the stability of the thermally-formed silicon oxide layer and the deposition conditions of boron-doped polysilicon. To understand the underlying principle of the passivation properties, the active dopant in-diffusion profiles following the thermal annealing are investigated, combined with an analysis of the microscopic structure. Based on PC1D simulation, we find that shallow in-diffusion of boron across a robust tunnel oxide forms a p-n junction and improves the passivation properties. Our findings can provide a pathway to understanding and designing high-quality hole-selective contacts based on the TOPCon structure for the development of highly efficient crystalline silicon solar cells.

Organic Anisotropic Excitonic Optical Nanoantennas.

Optical nanoantennas provide control of light at the nanoscale, which makes them important for diverse areas ranging from photocatalysis and flat metaoptics to sensors and biomolecular tweezing. They have traditionally been limited to metallic and dielectric nanostructures that sustain plasmonic and Mie resonances, respectively. More recently, nanostructures of organic J-aggregate excitonic materials have been proposed capable of also supporting nanooptical resonances, although their advance has been hampered from difficulty in nanostructuring. Here, the authors present the realization of organic J-aggregate excitonic nanostructures, using nanocylinder arrays as model system. Extinction spectra show that they can sustain both plasmon-like resonances and dielectric resonances, owing to the material providing negative and large positive permittivity regions at the different sides of its exciton resonance. Furthermore, it is found that the material is highly anisotropic, leading to hyperbolic and elliptic permittivity regions. Nearfield analysis using optical simulation reveals that the nanostructures therefore support hyperbolic localized surface exciton resonances and elliptic Mie resonances, neither of which has been previously demonstrated for this type of material. The anisotropic nanostructures form a new type of optical nanoantennas, which combined with the presented fabrication process opens up for applications such as fully organic excitonic metasurfaces.

Fully Bottom-Up Waste-Free Growth of Ultrathin Silicon Wafer via Self-Releasing Seed Layer.

The fabrication of ultrathin silicon wafers at low cost is crucial for advancing silicon electronics toward stretchability and flexibility. However, conventional fabrication techniques are inefficient because they sacrifice a large amount of substrate material. Thus, advanced silicon electronics that have been realized in laboratories cannot move forward to commercialization. Here, a fully bottom-up technique for producing a self-releasing ultrathin silicon wafer without sacrificing any of the substrate is presented. The key to this approach is a self-organized nanogap on the substrate fabricated by plasma-assisted epitaxial growth (plasma-epi) and subsequent hydrogen annealing. The wafer thickness can be independently controlled during the bulk growth after the formation of plasma-epi seed layer. In addition, semiconductor devices are realized using the ultrathin silicon wafer. Given the high scalability of plasma-epi and its compatibility with conventional semiconductor process, the proposed bottom-up wafer fabrication process will open a new route to developing advanced silicon electronics.

Effect of a multidisciplinary program to improve organ donation in the emergency department.

BACKGROUND AND IMPORTANCE: As the emergency department (ED) is an important source of potential organ donors, it may play an important role in the organ donation process. OBJECTIVE: To assess the effectiveness of the multidisciplinary organ donation improvement program (ODIP) on identifying potential donors and improving organ donation in South Korean EDs. DESIGN, SETTINGS, AND PARTICIPANTS: This study was a retrospective, observational study of the ED-inclusive ODIP implemented in 55 tertiary teaching hospitals contracted with the Korea Organ Donation Agency (KODA) since 2014. The inclusion criteria were: patients in the ED with a serious brain injury and futile prognosis or expected death of the patient within a few days, no contraindications for organ donation, and no objections registered in the donor registry. INTERVENTION: The ED-inclusive multidisciplinary approach was implemented to improve organ donation. It included regular meetings of the ODIP committee, hospital visits and staff education, improvement of notifications, and support of a coordination team. OUTCOMES MEASURE AND ANALYSIS: We assessed the changes in the number of deceased organ donors per year and notifications of potential brain-dead donors by medical staff after the implementation of the new ED-inclusive ODIP. The entire organ donation process was monitored and measured. RESULTS: There was a significant increase in deceased organ donors per million population after the implementation of the ED-inclusive multidisciplinary ODIP of KODA compared to the pre-intervention period: 5.21 vs. 9.72, difference 4.51 (95% confidence interval 2.11-6.91). During the study period, the proportion of deceased organ donors occurred from KODA-contracted hospitals increased from 25.3 to 50.3% in South Korea's total deceased organ donors. Emergency physicians of KODA-contracted hospitals notified increasingly more potential brain-dead donors each year throughout the study period (36 in 2014 vs. 135 in 2018). The longer the period contracted with KODA, the higher the potential brain-death identification rates (P < 0.001). CONCLUSION: In this retrospective study, the implementation of multidisciplinary ODIP in the ED led to significantly higher deceased organ donors per million population and awareness of potential brain-dead donors in South Korea.

Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells.

The formation of hydrogen blisters in the fabrication of tunnelling oxide passivating contact (TOPCon) solar cells critically degrades passivation. In this study, we investigated the formation mechanism of blisters during the fabrication of TOPCons for crystalline silicon solar cells and the suppression of such blisters. We tested the effects of annealing temperature and duration, surface roughness, and deposition temperature on the blister formation, which was suppressed in two ways. First, TOPCon fabrication on a rough surface enhanced adhesion force, resulting in reduced blister formation after thermal annealing. Second, deposition or annealing at higher temperatures resulted in the reduction of hydrogen in the film. A sample fabricated through low-pressure chemical vapor deposition at 580 °C was free from silicon-hydrogen bonds and blisters after the TOPCon structure was annealed. Remarkably, samples after plasma-enhanced chemical vapor deposition at 300, 370, and 450 °C were already blistered in the as-deposited state, despite low hydrogen contents. Analysis of the hydrogen incorporation, microstructure, and deposition mechanism indicate that in plasma-enhanced chemical vapor deposition (PECVD) deposition, although the increase of substrate temperature reduces the hydrogen content, it risks the increase of porosity and molecular-hydrogen trapping, resulting in even more severe blistering.

Moiré-fringeless Transparent Conductive Films with a Random Serpentine Network of Medium-Field Electrospun, Chemically Annealed Silver Microfibres.

Low-cost flexible transparent conductive films (TCFs) with direct writing of metal grids have been explored as a promising alternative to conventional indium-tin-oxide-based TCFs for future flexible electronics. However, flexible TCFs have raised technical concerns because of their disadvantages, such as low resolution, low productivity, poor optoelectrical performance, poor thermal stability, and adverse moiré fringes, which primarily arise from the superposition of periodic patterns. Herein, a facile and highly productive method to fabricate moiré-fringeless TCFs with good optoelectrical characteristics and excellent thermal stability is presented using a single-pass printed random serpentine network of medium-field electrospun silver microfibres (AgMFs) with a line width of 2.32 ± 0.97 µm by exploiting the random serpentine motion of medium-field electrospinning, enabling moiré-fringeless TCFs. The electrical in-plane anisotropy of the TCFs can be kept well below 110.44 ± 1.26% with the in situ junction formation of the AgMFs in the transverse direction. Combined thermal and chemical annealing of the AgMFs enables high productivity by reducing the thermal annealing time by 40%. The good optoelectrical performance, fair electrical in-plane anisotropy, high productivity, and superior thermal stability of the TCFs with the single-pass printed random serpentine network of medium-field electrospun AgMFs are suitable properties for flexible electronics such as ultra-large digital signage with LEDs.

Flexible/Rechargeable Zn-Air Batteries Based on Multifunctional Heteronanomat Architecture.

The increasing demand for advanced rechargeable batteries spurs development of new power sources beyond currently most widespread lithium-ion batteries. Here, we demonstrate a new class of flexible/rechargeable zinc (Zn)-air batteries based on multifunctional heteronanomat architecture as a scalable/versatile strategy to address this issue. In contrast to conventional electrodes that are mostly prepared by slurry-casting techniques, heteronanomat (denoted as "HM") framework-supported electrodes are fabricated through one-pot concurrent electrospraying (for electrode powders/single-walled carbon nanotubes (SWCNTs)) and electrospinning (for polyetherimide (PEI) nanofibers) process. Zn powders (in anodes) and rambutan-shaped cobalt oxide (Co3O4)/multiwalled carbon nanotube (MWCNT) composite powders (in cathodes) are used as electrode active materials for proof of concept. The Zn (or Co3O4/MWCNT) powders are densely packed and spatially bound by the all-fibrous HM frameworks that consist of PEI nanofibers (for structural stability)/SWCNTs (for electrical conduction) networks, leading to the formation of three-dimensional bicontinuous ion/electron transport channels in the electrodes. The HM electrodes are assembled with cross-linked polyvinyl alcohol/polyvinyl acrylic acid gel polymer electrolytes (acting as zincate ion crossover-suppressing, permselective separator membranes). Benefiting from its unique structure and chemical functionalities, the HM-structured Zn-air cell significantly improves mechanical flexibility and electrochemical rechargeability, which are difficult to achieve with conventional Zn-air battery technologies.

The vitamin D receptor expression in skeletal muscle of women with distal radius fracture.

We evaluated the vitamin D receptor (VDR) expression in the forearm flexor muscle of women with distal radius fracture. High VDR expression was associated with low appendicular lean mass index. INTRODUCTION: We aimed to evaluate the relationship between the VDR expression in the muscle cell and the muscle mass in women with a distal radius fracture (DRF). METHODS: We prospectively recruited 45 women over 50 years of age (mean age, 66 years) with DRF and acquired biopsy of the forearm flexor muscle. The muscle cross-sectional area (CSA) and VDR expression were measured using immunohistochemistry staining. The clinical parameters including grip strength, gait speed, body mass index (BMI), bone mineral density (BMD), and serum vitamin D levels were compared between patients grouped by appendicular lean mass index and were correlated with the VDR expression. RESULTS: Twelve patients (27%) showed a decreased appendicular lean mass index, less than the cut-off value of 5.4 kg/m2 which was suggested by the Asian Working Group for Sarcopenia. Patients with a low appendicular lean mass index had significantly lower muscle CSA (p = 0.037), but a higher VDR expression (p = 0.045) than those with higher indices. VDR expression was negatively correlated with BMI (r = - 0.417, p = 0.004) and appendicular lean mass index (r = - 0.316, p = 0.044). CONCLUSIONS: DRF patients with low appendicular lean mass index presented high VDR expression and low CSA in forearm muscle cells. This suggests that the VDR expression might be upregulated in the attempt to compensate for the decreasing muscle mass. Further studies are necessary to explore the role of VDR in the progression of sarcopenia.

Pyrolytic Carbon Hemiarthroplasty for Avascular Necrosis of the Metacarpal Head: A Case Report.

Avascular necrosis of the metacarpal head is a rare entity. Surgical interventions, such as curettage, bone-grafting, and osteotomy, have been reported in symptomatic patients. We present a patient who underwent pyrolytic carbon hemiarthroplasty of the metacarpal head and had satisfactory outcomes at 1-year follow-up.

Expression of vitamin D receptor in the subsynovial connective tissue in women with carpal tunnel syndrome.

Studies suggest that low vitamin D levels are associated with carpal tunnel syndrome. We aimed to evaluate whether level of vitamin D receptor expression in the endothelial cells of the subsynovial connective tissue is associated with clinical features of carpal tunnel syndrome. We obtained the subsynovial connective tissue from 52 women with carpal tunnel syndrome during surgery and performed immunohistochemical analysis of vitamin D receptors in the endothelial cells of the subsynovial connective tissue. We explored correlation of vitamin D receptor expression with clinical features of carpal tunnel syndrome, such as age, symptom duration, symptom severity and electrophysiological severity. Diverse range of vitamin D receptor expression was observed. Vitamin D receptor expression was independently associated with distal motor latency. This suggests that vitamin D receptor expression may be associated with disease progression, as prolonged distal motor latency reflects severity of the disease. Further studies are necessary to explore the role of vitamin D and vitamin D receptors in patients with carpal tunnel syndrome. LEVEL OF EVIDENCE: IV.

Structural evolution of tunneling oxide passivating contact upon thermal annealing.

We report on the structural evolution of tunneling oxide passivating contact (TOPCon) for high efficient solar cells upon thermal annealing. The evolution of doped hydrogenated amorphous silicon (a-Si:H) into polycrystalline-silicon (poly-Si) by thermal annealing was accompanied with significant structural changes. Annealing at 600 °C for one minute introduced an increase in the implied open circuit voltage (Voc) due to the hydrogen motion, but the implied Voc decreased again at 600 °C for five minutes. At annealing temperature above 800 °C, a-Si:H crystallized and formed poly-Si and thickness of tunneling oxide slightly decreased. The thickness of the interface tunneling oxide gradually decreased and the pinholes are formed through the tunneling oxide at a higher annealing temperature up to 1000 °C, which introduced the deteriorated carrier selectivity of the TOPCon structure. Our results indicate a correlation between the structural evolution of the TOPCon passivating contact and its passivation property at different stages of structural transition from the a-Si:H to the poly-Si as well as changes in the thickness profile of the tunneling oxide upon thermal annealing. Our result suggests that there is an optimum thickness of the tunneling oxide for passivating electron contact, in a range between 1.2 to 1.5 nm.

Olecranon Fractures Have Features of Osteoporotic Fracture.

BACKGROUND: To determine whether olecranon fractures have osteoporotic features such as age-dependent, low bone attenuation and low-energy trauma as a cause of injury. METHODS: Elbow computed tomography (CT) and medical record review were performed in 114 patients (53 males and 61 females) with acute olecranon fractures. The mean age was 57 years. Bone attenuation was measured on the central part of the olecranon on sagittal CT images avoiding the fracture, and on the distal humerus (distal metaphysis and medial and lateral condyles) on coronal CT images. We compared bone attenuation and causes of injury (high or low energy trauma) between younger (<50 years) and older (≥50 years) patients in each gender. Multiple regression analysis was performed to determine the effect of age and gender on bone attenuation. RESULTS: Mean bone attenuation in older male and female patients was significantly lower than in younger patients, except at the medial condyle in men. The proportion of low-energy trauma in older male patients was significantly higher than in younger male patients. In female patients, low-energy trauma was predominant in both younger and older patients. Age and female gender had significantly negative effects on bone attenuation. CONCLUSIONS: This study demonstrated that olecranon fractures have osteoporotic features, including age-dependent low bone attenuation and low-energy trauma as the predominant cause of injury. Our results suggest that osteoporosis evaluation should be considered for patients aged 50 years or more with olecranon fractures.

Low evaluation rate for osteoporosis among patients presenting with a rib fracture.

This study in a regional hospital setting found a low evaluation rate for osteoporosis among patients presenting with a rib fracture. Increased emphasis or education for osteoporosis evaluation may be necessary in case of rib fractures. INTRODUCTION: Rib fractures from a low-energy trauma are common in the elderly, and a history of rib fracture has been reported to increase the risk for a subsequent osteoporotic fracture. The purpose of this study was to evaluate how many of the patients presenting with an isolated rib fracture were being evaluated for osteoporosis and the risk for a subsequent fracture. METHODS: We retrospectively reviewed all patients aged 50 years or older who were diagnosed with a rib fracture between January 2011 and April 2016 at a regional tertiary care university hospital near Seoul, South Korea. We excluded those who had been treated for osteoporosis or those with other concomitant fractures or fractures from a motor vehicle accident or cancer. We evaluated the frequency of dual energy X-ray absorptiometry (DXA) scan examinations in these patients. RESULTS: There were 231 patients with isolated rib fractures (132 men and 99 women). The mean age was 65 years. Rib fractures were most commonly diagnosed at the emergency department and most of the patients were referred to the department of thoracic surgery for follow-up evaluations. Of these 231 patients, 29 (12%) had DXA examinations after the injury, and only 9 (4%) of them did so within 6 months. Physicians specializing in orthopedic surgery, family medicine, internal medicine, rehabilitation medicine, and emergency medicine were ordering the examination. CONCLUSIONS: This study in a regional hospital setting found a low evaluation rate for osteoporosis among patients presenting with a rib fracture. This study suggests that increased emphasis or education for osteoporosis evaluation may be necessary for physicians who are often referred to for care of rib fractures.

Enhancement of Light Absorption in Photovoltaic Devices using Textured Polydimethylsiloxane Stickers.

We designed and fabricated a random-size inverted-pyramid-structured polydimethylsiloxane (RSIPS-PDMS) sticker to enhance the light absorption of solar cells and thus increase their efficiency. The fabricated sticker was laminated onto bare glass and crystalline silicon (c-Si) surfaces; consequently, low solar-weighted reflectance values were obtained for these surfaces (6.88 and 17.2%, respectively). In addition, we found that incident light was refracted at the PDMS-air interface of each RSIPS, which redirected the incident power and significantly increased the optical path length in the RSIPS-PDMS sticker which was 14.7% greater than that in a flat-PDMS sticker. Moreover, we investigated power reflection and propagation through the RSIPS-PDMS sticker using a finite-difference time-domain method. By attaching an RSIPS-PDMS sticker onto both an organic solar cell (OSC) based on a glass substrate and a c-Si solar cell, the power conversion efficiency of the OSC and the c-Si solar cell were increased from 8.57 to 8.94% and from 16.2 to 17.9%, respectively. Thus, the RSIPS-PDMS sticker is expected to be universally applicable to the surfaces of solar cells to enhance their light absorption.

High-Temperature-Short-Time Annealing Process for High-Performance Large-Area Perovskite Solar Cells.

Organic-inorganic hybrid metal halide perovskite solar cells (PSCs) are attracting tremendous research interest due to their high solar-to-electric power conversion efficiency with a high possibility of cost-effective fabrication and certified power conversion efficiency now exceeding 22%. Although many effective methods for their application have been developed over the past decade, their practical transition to large-size devices has been restricted by difficulties in achieving high performance. Here we report on the development of a simple and cost-effective production method with high-temperature and short-time annealing processing to obtain uniform, smooth, and large-size grain domains of perovskite films over large areas. With high-temperature short-time annealing at 400 °C for 4 s, the perovskite film with an average domain size of 1 µm was obtained, which resulted in fast solvent evaporation. Solar cells fabricated using this processing technique had a maximum power conversion efficiency exceeding 20% over a 0.1 cm2 active area and 18% over a 1 cm2 active area. We believe our approach will enable the realization of highly efficient large-area PCSs for practical development with a very simple and short-time procedure. This simple method should lead the field toward the fabrication of uniform large-scale perovskite films, which are necessary for the production of high-efficiency solar cells that may also be applicable to several other material systems for more widespread practical deployment.

Use of a decision aid did not decrease decisional conflict in patients with carpal tunnel syndrome.

BACKGROUND: Although a model for shared decision-making is important for patient-centered care, decisional conflict can emerge when patients participate in the decision-making. A decision aid is proposed to provide information and to involve patients more comfortably in the decision-making process. We aimed to determine whether a decision aid helps patients with carpal tunnel syndrome (CTS) experience less decisional conflict regarding their decision-making for surgery. METHODS: Eighty patients with CTS were randomized into two groups. The test group was given a decision aid in addition to regular information and the control group regular information only. The decision aid consisted of a 6-min videoclip that explains diagnosis and information regarding surgery for CTS with other treatment options. We evaluated patients' decisional conflict regarding surgery, knowledge about CTS, and symptom severity as measured by the Disabilities of Arm, Shoulder, and Hand (DASH) Questionnaire. RESULTS: There was no difference in the decisional conflict scale (DCS) between both groups (p = 0.76). The test group had significantly better knowledge than the control group (p = 0.04). There was no correlation between the knowledge score and the DCS (p = 0.76). However, less severe symptoms were correlated with greater decisional conflict (r = -0.29, p = 0.02). CONCLUSIONS: We found that a decision aid does not reduce decisional conflict in patients with CTS, although it can help them be better informed. This study suggests that although a decision-aid is effective for patient education, doctor-patient communication should be more emphasized for patients with less severe symptoms, as they can have greater decisional conflict. TRIAL REGISTRATION: SNUBH Registry 1510/317-003 Registered November 13, 2015.

Effect of Heterocyclic Anchoring Sequence on the Properties of Dithienogermole-Based Solar Cells.

The synthesis and characterization of two new small molecular donor materials, DTGe(ThFBTTh2)2 and DTGe(FBTTh3)2, are presented for application in organic solar cells. These two materials represent structural evolutions of the high-efficiency, dithienogermole (DTGe)-cored small molecule DTGe(FBTTh2)2, in which the conjugation length in the backbone was extended by incorporating additional thiophene units. Using the same molecular framework, we have evaluated how the anchoring sequence of heterocyclic units influences material properties and function in solar cell devices. It was found that incorporating additional thiophene units into the backbone, regardless of the position in the molecular platform, caused a small reduction in band gaps; however, both highest occupied molecular orbitals and lowest unoccupied molecular orbital energy bands were at lower energies when the thiophenes were incorporated near the terminus of the molecule. The film morphologies of both materials could be controlled by either thermal or solvent vapor annealing to yield phase separation on the order of tens of nanometers and improved crystallinity. Peak power-conversion efficiencies of 3.6% and 3.1% were obtained using DTGe(ThFBTTh2)2 and DTGe(FBTTh3)2, after solvent vapor treatment and thermal annealing, respectively. Our study provides a detailed analysis of how the ordering sequence of heterocyclic building blocks influences the properties and function of organic solar cells.

Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films.

In this work, we present new results on the plasma processing and structure of hydrogenated polymorphous silicon (pm-Si:H) thin films. pm-Si:H thin films consist of a low volume fraction of silicon nanocrystals embedded in a silicon matrix with medium range order, and they possess this morphology as a significant contribution to their growth comes from the impact on the substrate of silicon clusters and nanocrystals synthesized in the plasma. Quadrupole mass spectrometry, ion flux measurements, and material characterization by transmission electron microscopy (TEM) and atomic force microscopy all provide insight on the contribution to the growth by silicon nanocrystals during PECVD deposition. In particular, cross-section TEM measurements show for the first time that the silicon nanocrystals are uniformly distributed across the thickness of the pm-Si:H film. Moreover, parametric studies indicate that the best pm-Si:H material is obtained at the conditions after the transition between a pristine plasma and one containing nanocrystals, namely a total gas pressure around 2 Torr and a silane to hydrogen ratio between 0.05 to 0.1. From a practical point of view these conditions also correspond to the highest deposition rate achievable for a given RF power and silane flow rate.