Safety of Combined Fractional Microneedle Radiofrequency and CO2 as an Early Intervention for Inflammatory Acne and Scarring Treated With Concomitant Isotretinoin.

BACKGROUND: Fractional microneedle radiofrequency (FMRF) systems are popular options for treating acne scars. However, treatment efficacy when used in combination with traditional ablative fractional laser (AFL) and the safety profile with concomitant use of isotretinoin remain unknown. OBJECTIVE: The aim of this study was to assess the safety and efficacy of an early intervention combination treatment protocol for inflammatory acne and acne scars. MATERIALS AND METHODS: The electronic records of 71 patients with inflammatory acne and acne scars were included in this retrospective observational study. Data were collected for all patients who received combination FMRF and AFL. Within the study group, 43 patients were receiving low-dose isotretinoin or had completed isotretinoin within the past 3 weeks. RESULTS: The mean Scar Global Assessment score significantly decreased after 3 sessions of combination treatment (n = 71). Patients with inflammatory acne showed a significant decrease in the number of inflammatory lesions (n = 30). Patients with concomitant low-dose isotretinoin use reported a further decrease in Scar Global Assessment score (n = 43). There were no reported persistent side effects, including prolonged inflammatory reaction or scarring. CONCLUSION: Combination treatment with FMRF and AFL is an effective and well-tolerated treatment modality for acne scars and inflammatory acne.

Folding-Generated Molecular Tubes Containing One-Dimensional Water Chains.

A series of indolocarbazole-pyridine (IP) oligomers were prepared that fold into helical conformations, and their folding features in solution and in the solid state were revealed. Helical folding of these IP foldamers is induced by dipolar interactions through the ethynyl bond and π-stacking between two repeating units. Upon helical folding, (1)H NMR signals of aromatic protons were significantly shifted upfield by Δδ = 0.5-2.2 ppm. In addition, hypochromic shifts and fluorescence quenching were observed in the absorption and emission spectra. X-ray crystal structures clearly demonstrated that IP foldamers folded to helical structures with cylindrical internal cavities wherein 3 or 5 water molecules were occupied by hydrogen-bonding interactions in a 1-D array, reminiscent of transmembrane water channels, called aquaporins.

Comparative expression of matrix metalloproteinases in internal malignancies and paired cutaneous metastatic lesions.

BACKGROUND: Matrix metalloproteinase (MMP), tissue inhibitor of metalloproteinase (TIMP), and membrane-type 1 matrix metalloproteinase (MT1-MMP) are thought to be involved in the destruction of basement membrane and stromal invasion by cancer cells. OBJECTIVE: The aim of this study was to identify and compare MMP and TIMP expression in internal malignancies and paired cutaneous metastatic lesions. MATERIALS AND METHODS: We compared the expression of MMP-2, MMP-9, MT1-MMP, and TIMP-2 in the internal malignancy and paired cutaneous metastatic lesion using immunohistochemical stains. RESULTS: The cutaneous metastatic lesions expressed significantly more MMP-2, MMP-9, and MT1-MMP and significantly less TIMP-2 than did the paired internal malignancies. In breast cancer, cutaneous metastatic lesions expressed significantly more MMP-9 and significantly less TIMP-2 than did the primary breast cancer lesion. In lung cancer, the cutaneous metastatic lesion expressed significantly more MMP-2 and MT1-MMP than did the primary lesion. In stomach cancer, the cutaneous metastatic lesion expressed significantly less TIMP-2 than did the primary lesion. CONCLUSIONS: Our study demonstrates that cutaneous metastatic lesions have different MMPs and TIMP-2 expression patterns compared with their paired internal malignancies. Also, MMPs and TIMP-2 expression differs according to the type of primary cancer.

Role of hepatitis B surface antigen (HBsAg) in identifying true inactive HBsAg carriers infected with genotype C hepatitis B virus.

BACKGROUND: Inactive and active phases of hepatitis B e antigen-negative chronic hepatitis B virus (HBV) infection are diagnosed by serum HBV DNA levels, with cutoff at 2000 IU/mL. However, it is difficult to distinguish inactive carriers at a single time point because HBV DNA levels can transiently decrease to <2000 IU/mL even in noninactive carriers. GOALS: We aimed to establish the role of serum hepatitis B surface antigen (HBsAg) in identifying "true inactive carriers" among treatment-naive genotype C HBV-infected patients with low viremia. STUDY: A total of 133 hepatitis B e antigen-negative carriers with serum HBV DNA levels of <2000 IU/mL and normal alanine aminotransferase levels were enrolled and followed up for >12 months. RESULTS: Forty patients (30.1%) were classified as noninactive carriers (HBV DNA ≥2000 IU/mL and/or alanine aminotransferase >40 IU/L) during 12 months from enrollment. No baseline serum HBV DNA levels could identify true inactive carriers with 100% specificity, whereas baseline serum HBsAg levels (50 IU/mL) identified true inactive carriers with 100% specificity and 29% detection rate. Detection rate increased when different cutoff levels were applied to different age groups according to median age (46 y). It was comparable in both younger and older groups (37.2% vs. 38%) even when HBsAg cutoff level was increased in the former (400 vs. 50 IU/mL). Furthermore, none reversed to noninactive phase during long-term follow-up when these cutoff levels were applied. CONCLUSIONS: Baseline serum HBsAg levels at a single time point can identify persistently true inactive carriers, with different cutoff levels according to age.

Bio-inspired bending actuator for controlling conical nose shape using piezoelectric patches.

In this paper, a bio-inspired bending actuator was designed and fabricated using piezoelectric patches and cantilever-shaped beam for controlling nose shape. The aim of this study is to investigate the use of the bending actuator. PZT and single crystal PMN-PT actuators were used to generate translational strain and shear stress. The piezoelectric patches were attached on the clamped cantilever beam to convert their translational strains to bending motion of the beam. First, finite element analysis was performed to identify and to make an accurate estimate of the feasibility on the bending actuation by applying various voltages and frequencies. Based on the results of the FEM analysis, the experiments were also performed. Static voltages and dynamic voltages with various frequencies were applied to the bending actuators with PZTs and PMN-PTs, and the rotation angles of the nose connected to the top of bending actuators were measured, respectively. As the results, the bending actuator using PMN-PT patches showed better performances in all cases. With the increases of signal frequency and input voltage, the rotation angle also found to be increased. Especially at the frequency of 5 Hz and input voltage of 600 V, the nose generated the maximum rotation angle of 3.15 degree.

Comparison of non-ablative and ablative fractional laser treatments in a postoperative scar study.

BACKGROUND AND OBJECTIVE: Postoperative scarring after thyroidectomy is a problem for both patients and clinicians. Recently, both non-ablative and ablative fractional laser (NFL and AFL) systems have attracted attention as potential therapies for the revision of thyroidectomy scars. The present split-scar study was designed to directly compare the efficacy of these two methods for the treatment of post-thyroidectomy scars. STUDY DESIGN/MATERIALS AND METHODS: Twenty females (mean age 42.1 years, range 22-55) with scarring 2-3 months post-thyroidectomy were enrolled in the study. One half of the scar (chosen at random) was treated with NFL and the other half was treated with AFL. In each case, two treatments were given at 2-month intervals. Clinical photographs were taken at baseline, before each treatment, and at the final 3-month evaluation. Independent clinician grading of improvement and patient satisfaction were measured on a quartile scale. Color (erythema and melanin indices) and scar hardness were measured at baseline and at three months post-treatment with a dermaspectrometer and durometer, respectively. RESULTS: The mean clinical improvement grades for AFL and NFL were highly similar, 2.45 ± 0.99 and 2.35 ± 0.85, respectively, without statistical significance (P = 0.752). However, NFL treatment resulted in statistically significant changes in erythema and pigmentation (P = 0.035 and P = 0.003, respectively), and skin hardness was significantly reduced after AFL treatment (P = 0.026). CONCLUSIONS: Clinical improvement was not significantly different between the two systems; however, AFL was better at reducing scar hardness whereas NFL was superior for lightening color. These data suggest that a study assessing the feasibility of a combined approach for the revision of post-thyroidectomy scarring might be warranted.

The Effect of Time Spent on Online Gaming on Problematic Game Use in Male: Moderating Effects of Loneliness, Living Alone, and Household Size.

OBJECTIVE: This study aimed to investigate the association between gaming time and problematic game use (PGU) within a large sample of Korean male gamers and to examine the potential moderating effects of loneliness, living alone, and household size. METHODS: This study employed data from 743 male gamers from the National Mental Health Survey 2021, a nationally representative survey of mental illness conducted in South Korea. Self-reported data on the average gaming time per day, severity of PGU, loneliness, living alone, and household size were used. RESULTS: Gaming time was positively associated with PGU and this relationship was significantly moderated by loneliness such that the positive effect of gaming time on PGU was greater when the levels of loneliness were high. The three-way interaction effect of gaming time, loneliness, and living alone was also significant, in that the moderating effect of loneliness on the relationship between gaming time and PGU was significant only in the living alone group. However, household size (i.e., number of housemates) did not moderate the interaction between gaming time and loneliness among gamers living with housemates. CONCLUSION: These results suggest the importance of considering loneliness and living arrangements of male gamers, in addition to gaming time, in identifying and intervening with individuals at heightened risk of PGU.

Knee derangements: comparison of isotropic 3D fast spin-echo, isotropic 3D balanced fast field-echo, and conventional 2D fast spin-echo MR imaging.

PURPOSE: To compare diagnostic performance, subjective image quality, and artifacts of isotropic three-dimensional (3D) intermediate-weighted (IW) fast spin-echo (SE), isotropic 3D balanced fast field-echo (FFE), and conventional two-dimensional (2D) fast SE 3.0-T MR sequences in evaluation of cartilage, ligaments, menisci, and osseous knee structures in symptomatic patients. MATERIALS AND METHODS: Institutional review board approval and waiver of informed consent were obtained for this HIPAA-compliant study. One hundred MR studies, each with three data sets (3D IW fast SE, 3D balanced FFE, 2D fast SE), were reviewed retrospectively. Two radiologists independently evaluated images for cartilaginous defects, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial meniscus (MM), lateral meniscus (LM) tears, subchondral bone marrow signal abnormalities, subjective image quality, and image artifacts. Arthroscopic results were the reference standard. Statistical analysis was performed to calculate interobserver agreement and compare diagnostic performance of sequences. RESULTS: Sensitivity and specificity were greater than 85% for all lesions. For cartilaginous defects, sensitivity of 3D IW fast SE was significantly greater than that of 3D balanced FFE (95.5% vs 89.7%). Sensitivity of 3D IW fast SE and 2D fast SE for MM, LM, and ACL tears tended to be greater than that of 3D balanced FFE. IW fast SE had a higher detection rate for subchondral bone marrow signal abnormality than did 3D balanced FFE (34% vs 21%); it also had the best image quality and fewest artifacts, followed by 2D fast SE and 3D balanced FFE. Interobserver agreement was excellent for evaluation of all intraarticular structures (κ = 0.85-1) and good to excellent for detection of subchondral bone marrow signal abnormality (κ = 0.76-0.91). CONCLUSION: The performance of IW fast SE is superior to that of balanced FFE in evaluation of cartilaginous defects, with no significant difference in performance between 2D fast SE, 3D IW fast SE, and 3D balanced FFE in evaluation of meniscal and ligament tears. Subchondral bone marrow signal abnormality is more easily seen on 3D IW fast SE images, with better subjective image quality and fewer artifacts, than on images obtained with other techniques.

Effect of subdermal 1,444-nm pulsed neodymium-doped yttrium aluminum garnet laser on the nasolabial folds and cheek laxity.

BACKGROUND: Wrinkle formation usually accompanies skin aging. In particular, accentuated nasolabial folds and loss of elasticity are early signs of skin aging. The use of 1,444-nm pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers has increased in popularity. OBJECTIVE: To evaluate the safety and efficacy of a novel 1,444-nm pulsed Nd:YAG laser in the treatment of NLF and cheek laxity using subdermal laser therapy. METHODS: Ten Korean patients with moderate to severe NLF were enrolled. Each received a single treatment session with a 1,444-nm Nd:YAG laser. Two blinded physicians evaluated clinical improvement by rating comparative photographs on a 5-point scale. Efficacy was also assessed by measuring elasticity and roughness. Skin biopsies were performed on five volunteers before treatment and 3 months after treatment. RESULTS: The 1,444-nm Nd:YAG laser effectively promoted clinical improvement of NLF and cheek laxity (p < .05). Significant differences in elasticity and roughness were observed (p < .05). Epidermal proliferation was stimulated as demonstrated by increases in epidermal thickness and Ki-67 expression (p < .05). Quantitative image analyses of pre- and post-treatment biopsies revealed that collagen fibers increased from baseline (p > .05). Transforming growth factor beta and heat shock protein-70 messenger RNA levels quantified using real-time reverse transcriptase polymerase chain reaction increased significantly from baseline (p < .05). CONCLUSION: The 1,444-nm Nd:YAG laser is an effective treatment modality with minimal complications for the treatment of NLF and cheek laxity, but further research with a larger group of patients is needed to confirm these findings.

Qualitative and quantitative assessment of wrist MRI at 3.0T: comparison between isotropic 3D turbo spin echo and isotropic 3D fast field echo and 2D turbo spin echo.

BACKGROUND: Isotropic three-dimensional (3D) magnetic resonance imaging (MRI) has been applied to various joints. However, comparison for image quality between isotropic 3D MRI and two-dimensional (2D) turbo spin echo (TSE) sequence of the wrist at a 3T MR system has not been investigated. PURPOSE: To compare the image quality of isotropic 3D MRI including TSE intermediate-weighted (VISTA) sequence and fast field echo (FFE) sequence with 2D TSE intermediate-weighted sequence of the wrist joint at 3.0 T. MATERIAL AND METHODS: MRI was performed in 10 wrists of 10 healthy volunteers with isotropic 3D sequences (VISTA and FFE) and 2D TSE intermediate-weighted sequences at 3.0 T. The signal-to-noise ratio (SNR) was obtained by imaging phantom and noise-only image. Contrast ratios (CRs) were calculated between fluid and cartilage, triangular fibrocartilage complex (TFCC), and the scapholunate ligament. Two radiologists independently assessed the visibility of TFCC, carpal ligaments, cartilage, tendons and nerves with a four-point grading scale. Statistical analysis to compare CRs (one way ANOVA with a Tukey test) and grades of visibility (Kruskal-Wallis test) between three sequences and those for inter-observer agreement (kappa analysis) were performed. RESULTS: The SNR of 2D TSE (46.26) was higher than those of VISTA (23.34) and 3D FFE (19.41). CRs were superior in 2D TSE than VISTA (P = 0.02) for fluid-cartilage and in 2D TSE than 3D FFE (P < 0.01) for fluid-TFCC. The visibility was best in 2D TSE (P < 0.01) for TFCC and in VISTA (P = 0.01) for scapholunate ligament. The visibility was better in 2D TSE and 3D FFE (P = 0.04) for cartilage and in VISTA than 3D FFE (P < 0.01) for TFCC. The inter-observer agreement for the visibility of anatomic structures was moderate or substantial. CONCLUSION: Image quality of 2D TSE was superior to isotropic 3D MR imaging for cartilage, and TFCC. 3D FFE has better visibility for cartilage than VISTA and VISTA has superior visibility for TFCC to 3D FFE and the visibility for scapholunate ligament was best on VISTA.

The "bridging sign": a MR finding for combined full-thickness tears of the subscapularis tendon and the supraspinatus tendon.

BACKGROUND: In daily practice, we discovered one of the secondary magnetic resonance (MR) findings of the subscapularis (SSC) tendon tear, the "bridging sign", which has not been previously described. PURPOSE: To describe the "bridging sign" on shoulder MR imaging and its radiological and clinical significance in patients with SSC tendon tear. MATERIAL AND METHODS: Twenty-nine patients who had undergone shoulder arthroscopy and had full-thickness tear of the subscapularis tendon were enrolled. The medical records of the 29 patients were retrospectively reviewed for the duration of shoulder pain, rotator cuff tears, and associated arthroscopic findings: biceps tendon abnormality and superior glenoid labral tear. Then, preoperative shoulder MR images were retrospectively reviewed for the presence or absence of the "bridging sign" and associated MR findings: periarticular fluid and fatty atrophy of the supraspinatus and subscapularis muscles. The type of rotator cuff tear associated with the "bridging sign" was assessed and the sensitivity, specificity, and accuracy of the "bridging sign" for the diagnosis of a certain type of rotator cuff tear were calculated. Associated arthroscopic and MR findings and mean duration of the shoulder pain between the patients with and without the "bridging sign" were compared. RESULTS: The "bridging sign" was seen in 17 of 29 patients and corresponded to a complex of the torn and superomedially retracted subscapularis tendon, coracohumeral ligament, and superior glenohumeral ligament, adhered to the anterior margin of the torn supraspinatus (SSP) tendon on arthroscopy. All patients with the "bridging sign" had combined full-thickness tear (FTT) of the cranial 1/2 portion of the subscapularis tendon and anterior 1/2 portion of the SSP tendon. The sensitivity, specificity, and accuracy of the "bridging sign" for the diagnosis of combined FTTs of the SSC tendon and anterior portion of the SSP tendon were 81.0%, 100%, and 86.2%, respectively. The patients with the "bridging sign" had longer duration of shoulder pain and more frequent associated arthroscopic and MR findings than the patients without the "bridging sign". CONCLUSION: The "bridging sign" is a highly specific finding for combined full-thickness tears of the subscapularis tendon and anterior portion of the supraspinatus tendon, associated with more chronic shoulder pain and more sever rotator cuff tear.

Chlortetracycline degradation by photocatalytic ozonation in the aqueous phase: mineralization and the effects on biodegradability.

Chlortetracycline (CTC) is a hazardous material in aquatic environments. This study was focused on optimization of photocatalytic ozonation processes for removal of CTC from wastewater at pH 2.2 and 7.0. In this study, the tested processes for CTC removal were arranged from the least efficient to the most efficient as: UV, UV/TiO2, O3, O3/UV and O3/UV/TiO2. Ozonation efficiency was due to ozone affinity for electron-rich sites on the CTC molecule. In the O3/UV and O3/UV/TiO2 processes, efficiency was increased by the photolysis of CTC and generation of *OH. At pH 7.0, all the processes were more efficient for CTC degradation than at pH 2.2 due to CTC speciation, ozone decay to *OH and the attractions between ionized CTC and TiO2 particles. UV/O3 at pH 7.0 showed an additive effect while other combination processes showed a synergistic effect that resulted in higher rates of reactions than the sums of individual reaction rates. The TOC removal ranged from 8% to 41% after one hour of reaction, with the above-mentioned order of efficiency. The biodegradability increased rapidly during the early minutes of the reaction. A reaction time of 10-15 min was sufficient for near maximum biodegradability, making these processes good pretreatments for the biological processes.

Mesophilic co-digestion of palm oil mill effluent and empty fruit bunches.

The palm oil mill industry generates palm oil mill effluent (POME) and empty fruit bunches (EFB) as by-products. This study reports the mesophilic co-digestion of POME with EFB. The biochemical methane potential (BMP) of POME and EFB was 0.397 L CH4/g volatile solids (VS) and 0.264 L CH4/g VS, respectively. In a series of batch tests at various EFB to POME ratios, the maximum methane production rate was achieved at an EFB:POME ratio of 0.25-0.31:1. Performance data from lab-scale digesters confirmed the positive synergism by the addition of EFB to POME, which was attributed to the balanced chemical composition, for example the chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio. The EFB addition enhanced the acceptable organic loading rate, methane production, COD removal, and microbial activity. The mesophilic co-digestion of POME and EFB promises to be a viable recycling method to alleviate pollution problems and recover renewable energy in the palm oil mill industry.

The tradeoff between plasmonic enhancement and optical loss in silicon nanowire solar cells integrated in a metal back reflector.

We perform a systematic numerical study to characterize the tradeoff between the plasmonic enhancement and optical loss in periodically aligned, silicon nanowire (SiNW) arrays integrated with a silver back reflector (Ag BR). Optimizing the embedded depth of the wire bottoms into a silver reflector achieved a highly efficient SiNW solar cell. Compared to the SiNW solar cell employing a flat back reflector, the embedded depth of ~20 nm resulted in the relative increase of ~5% in ultimate solar cell efficiency.

A split-face comparison of a fractional microneedle radiofrequency device and fractional carbon dioxide laser therapy in acne patients.

BACKGROUND: A number of lasers and light-based devices have been reported as promising treatment options for acne vulgaris. OBJECTIVE: To evaluate the efficacy and safety of fractional microneedle radiofrequency (MRF) device treatment compared to CO(2) fractional laser system (FS) for the treatment of acne vulgaris. METHODS: Twenty healthy subjects underwent full-face treatment for acne vulgaris with CO(2) FS and MRF device. For each subject, two passes of CO(2) FS with a pulse energy setting of 80 mJ and a density of 100 spots/cm(2) were used on one side, and two passes of MRF device with a intensity of 8, density of 25 MTZ/cm(2), and a depth of 1.5-2.5 mm were used on the other. Patients were evaluated 3 months postoperatively and were also photographed. RESULTS: Most of the patients improved based on clinical and photographic assessments 3 months after the treatment. No significant differences in physician-measured parameters, patient ratings, or intraoperative pain ratings were found, although downtime was significantly longer for the CO(2) FS treated side. CONCLUSIONS: MRF device and CO(2) FS can be used for acne vulgaris patients and MRF device is more convenient than CO(2) FS because of its short downtime.

Gut microbiota modulation and gold nanoparticle-mediated photothermal therapy for treatment of recalcitrant acne.

Recent studies highlight that gut dysbiosis, an imbalanced state of intestinal microbiota, exacerbates skin inflammation. Here, we showed the presence of gut microbiota alterations in two patients with recalcitrant acne and investigated the impact of its therapeutic modulation together with gold nanoshell-mediated photothermal therapy (gold PTT).

Reduction of Ethyl Carbamate in an Alcoholic Beverage by CRISPR/Cas9-Based Genome Editing of the Wild Yeast.

Ethyl carbamate (EC) is a naturally occurring substance in alcoholic beverages from the reaction of ethanol with urea during fermentation and storage. EC can cause dizziness and vomiting when consumed in small quantities and develop kidney cancer when consumed in excess. Thus, the reduction of EC formation in alcoholic beverages is important for food safety and human health. One of the strategies for reducing EC contents in alcoholic beverages is developing a new yeast starter strain to enable less formation of EC during fermentation. In this study, we isolated a polyploid wild-type yeast Saccharomyces cerevisiae strain from the Nuruk (Korean traditional grain-based inoculum of wild yeast and mold) and developed a starter culture by genome engineering to reduce EC contents in alcoholic beverages. We deleted multiple copies of the target genes involved in the EC formation in the S. cerevisiae by a CRISPR/Cas9-based genome editing tool. First, the CAR1 gene encoding for the arginase enzyme responsible for the formation of urea was completely deleted in the genome of S. cerevisiae. Additionally, the GZF3 gene encoding the transcription factor controlling expression levels of several genes (DUR1, 2, and DUR3) related to urea absorption and degradation was deleted in S. cerevisiae to further reduce the EC formation. The effects of gene deletion were validated by RT-qPCR to confirm changes in transcriptional levels of the EC-related genes. The resulting strain of S. cerevisiae carrying a double deletion of CAR1 and GZF3 genes successfully reduced the EC contents in the fermentation medium without significant changes in alcohol contents and fermentation profiles when compared to the wild-type strain. Finally, we brewed the Korean traditional rice wine Makgeolli using the double deletion strain of S. cerevisiae dCAR1&GZF3, resulting in a significant reduction of the EC content in Makgeolli up to 41.6% when compared to the wild-type strain. This study successfully demonstrated the development of a starter culture to reduce the EC formation in an alcoholic beverage by CRISPR/Cas9 genome editing of the wild yeast.

Black Si Photocathode with a Conformal and Amorphous MoSx Catalytic Layer Grown Using Atomic Layer Deposition for Photoelectrochemical Hydrogen Evolution.

We demonstrated how the photoelectrochemical (PEC) performance was enhanced by conformal deposition of an amorphous molybdenum sulfide (a-MoSx) thin film on a nanostructured surface of black Si using atomic layer deposition (ALD). The a-MoSx is found to predominantly consist of an octahedral structure (S-deficient metallic phase) that exhibits high electrocatalytic activity for the hydrogen evolution reaction with a Tafel slope of 41 mV/dec in an acid electrolyte. The a-MoSx has a smaller work function (4.0 eV) than that of crystalline 2H-MoS2 (4.5 eV), which induces larger energy band bending at the p-Si surface, thereby facilitating interface charge transfer. These features enabled us to achieve an outstanding kinetic overpotential of ∼0.2 V at 10 mA/cm2 and an onset potential of 0.27 V at 1 mA/cm2. Furthermore, the a-MoSx layer provides superior protection against corrosion of the Si surface, enabling long-term PEC operation of more than 50 h while maintaining 87% or more performance. This work highlights the remarkable advantages of the ALD a-MoSx layer and leads to a breakthrough in the architectural design of PEC cells to ensure both high performance and stability.

Optical properties of Si microwires combined with nanoneedles for flexible thin film photovoltaics.

A combined wire structure, made up of longer periodic Si microwires and short nanoneedles, was prepared to enhance light absorption using one-step plasma etching via lithographical patterning. The combined wire array exhibited light absorption of up to ~97.6% from 300 to 1100 nm without an anti-reflection coating. These combined wire arrays on a Si substrate were embedded into a transparent polymer. A large-scale wire-embedded soft film was then obtained by peeling the polymer-embedded wire portion from the substrate. Optically attractive features were present in these soft films, making them suitable for use in flexible silicon solar cell applications.

Effective method to extract optical bandgaps in Si nanowire arrays.

A simple method to extract the optical bandgap of Si nanowire (SiNW) arrays that utilizes the reflection spectra of freestanding SiNW arrays is presented in this Letter. At a fixed nanowire diameter, three different wire lengths reproducibly formed a cross point in their reflectance curve plots. The cross point wavelength corresponded to the optical bandgap, as verified by the classical Tauc's model. The optical bandgap of the SiNW arrays (112 nm in average diameter) was measured to be ~1.19 eV, which is larger than the ~1.08 eV bandgap of bulk Si. Further decreasing the wire diameter to 68 nm caused an increase of the bandgap to ~1.24 eV, which is closer to the optimal bandgap (~1.40 eV) required to achieve the highest conversion efficiency in single-junction photovoltaic devices. Our method suggests that the multijunction tandem structure can be realized via control of the diameter of SiNW arrays.