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It is well‐known that the alkali doping of polycrystalline Cu2ZnSn(S,Se)4 (CZTSSe) and Cu(In,Ga)(Se,S)2 has a beneficial influence on the device performance and there are various hypotheses about the principles of performance improvement. This work clearly explains the effect of Na doping on the fill factor (FF) rather than on all of the solar cell parameters (open‐circuit voltage, FF, and sometimes short circuit current) for overall performance improvement. When doping is optimized, the fabricated device shows sufficient built‐in potential and selects a better carrier transport path by the high potential difference between the intragrains and the grain boundaries. On the other hand, when doping is excessive, the device shows low contact potential difference and FF and selects a worse carrier transport path even though the built‐in potential becomes stronger. The fabricated CZTSSe solar cell on a flexible metal foil optimized with a 25 nm thick NaF doping layer achieves an FF of 62.63%, thereby clearly showing the enhancing effect of Na doping.

In this study, highly efficient and flexible Na-doped kesterite Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells with an efficiency of over 8% were developed. A CZTSSe thin film was deposited on a flexible Mo foil using metal precursors with varying thickness of the NaF layers on the CZTSSe thin film. The sample maintained 92.2% of its performance after 1000 bending cycles with a bending radius of 12 mm. To investigate defect passivation effect of Na doping through the electrical properties of Na-passivated grain boundaries (GBs), the cells were examined by scanning probe microscopy. Downward band bending was observed at GBs in the Na-sufficient CZTSSe absorber layers; that is, Na enhanced the potential barrier at the CZTSSe GBs in the solar cells and the separation of carriers. The carrier separation increased under illuminated condition. Moreover, the surface photovoltage (SPV) of the cells was measured at laser wavelengths of 405, 532, and 640 nm using photo-assisted Kelvin probe force microscopy to investigate the photogenerated carrier transport in Na-passivated CZTSSe solar cells. The Na content strongly affected the photo-induced changes in the carrier behavior. A cell with a sufficiently Na-doped CZTSSe absorber layer exhibited a large SPV with a maximum value of 46 meV under illumination, whereas Na-deficient samples showed a lower SPV, indicating that Na passivates defects that act as recombination sites. A photo-induced defect passivation effect was observed in a cell with optimal Na content under 405 nm wavelength illuminated condition, which resulted in charge accumulation at the absorber surface.

It is well‐known that the alkali doping of polycrystalline Cu2ZnSn(S,Se)4 (CZTSSe) and Cu(In,Ga)(Se,S)2 has a beneficial influence on the device performance and there are various hypotheses about the principles of performance improvement. This work clearly explains the effect of Na doping on the fill factor (FF) rather than on all of the solar cell parameters (open‐circuit voltage, FF, and sometimes short circuit current) for overall performance improvement. When doping is optimized, the fabricated device shows sufficient built‐in potential and selects a better carrier transport path by the high potential difference between the intragrains and the grain boundaries. On the other hand, when doping is excessive, the device shows low contact potential difference and FF and selects a worse carrier transport path even though the built‐in potential becomes stronger. The fabricated CZTSSe solar cell on a flexible metal foil optimized with a 25 nm thick NaF doping layer achieves an FF of 62.63%, thereby clearly showing the enhancing effect of Na doping., The effects of Na doping on polycrystalline flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells are analyzed. When doping is excessive, the device shows low contact potential difference and fill factor and selects a worse carrier transport path even though the built‐in potential becomes stronger. On the other hand, the optimized CZTSSe solar cell clearly shows the enhancing effect of Na doping.

In article number 1903085, Woo‐Lim Jeong, Kyung‐Pil Kim, Dong‐Seon Lee, and co‐workers analyze the effects of Na doping on polycrystalline flexible CZTSSe solar cells. When doping is excessive, a device shows low contact potential difference and fill factor and selects a worse carrier transport path even though the built‐in potential becomes stronger. On the other hand, the optimized CZTSSe solar cell clearly showed the enhancing effect of Na doping. [Image: see text]

Environment-friendly Cu(In,Ga)Se2 (CIGS) solar cells requires the replacement of Cd-containing buffers with non-toxic materials. Zn(O,S) buffers have been developed and yielded even better efficiency than CdS-buffered CIGS thin-film solar cells [23.35%, Ref. [6]]. In this work, we studied band offsets of Zn(O,S) and CIGS interfaces. The Cd-free buffer layers were deposited with 1.0%, 1.3%, and 1.6% oxygen (O2) gas partial pressure during the deposition. Effects of the oxygen partial pressure on the structure and electronic properties of the devices were investigated by micro-Raman scattering spectroscopy and Kelvin probe force microscopy, respectively. We achieved depth-profiling of spatial work function mapping across the interface between the absorbers and the buffers. The best efficiency sample, grown using 1.3% of oxygen, showed 80 mV spike-like band offsets. We propose that the efficiency can be improved through tailoring of the band offsets at the interface as well as improving the absorber and the buffer materials.

This study aimed to assess the relationship between coexisting lymphocytic thyroiditis and T-N stages of papillary thyroid carcinoma (PTC) by histopathological analysis.The study included 653 patients who underwent thyroid surgery for PTC at our hospital. Each case was classified as either Hashimoto's thyroiditis (HT), non-Hashimoto type of lymphocytic thyroiditis (NHLT), or normal according to the histopathology of thyroid parenchyma. Patient age, gender, surgical modality, location, T stage, N stage, multifocality and bilaterality were compared according to the histopathology.The prevalence of coexisting lymphocytic thyroiditis was 25.8% (169/653); HT (7.5%, 49/653) and NHLT (18.3%, 120/653). There were no significant differences in T stage, N stage, multifocality and bilaterality with regard to coexisting lymphocytic thyroiditis, regardless of whether HT and NHLT were considered collectively or discretely. Primary tumor size (p 0.0001), location (p = 0.0011), N stage (p 0.0001), multifocality (p 0.0001) and bilaterality (p 0.0001) differed significantly according to T stage, and gender (p = 0.0193), primary tumor size (p 0.0001), T stage (p 0.0001), multifocality (p 0.0001) and bilaterality (p 0.0001) differed significantly according to N stage.PTC patients with coexisting lymphocytic thyroiditis did not differ from those with normal parenchyma in terms of T stage, N stage, multifocality and bilaterality.

Purpose To maintain the patient's quality of life, surgeons strive to preserve the sphincter during rectal cancer surgery. This study evaluated the oncologic safety of a sphincter-saving resection with a distal resection margin (DRM) 1 cm), the 5-year cancer-specific survival rates were 81.57% and 80.03% (P = 0.8543), the 5-year local recurrence rates were 6.69% and 9.52% (P = 0.3981), and the 5-year systemic recurrence rates were 19.46% and 23.11% (P = 0.5750), respectively. Conclusion This study showed that the close DRM itself should not be a contraindication for a sphincter-saving resection for T3 mid- or low-rectal cancer without radiotherapy. However, a prospective randomized controlled trial including the effect of adjuvant therapy will be needed.

PURPOSE The serum level of carcinoembryonic antigen (CEA) is a clinical prognostic factor in the follow-up evaluation of patients with colon cancer. We aimed to evaluate the prognostic significance of the rate of decrease of the perioperative serum CEA level in patients with colon cancer after a curative resection. METHODS A total of 605 patients who underwent a curative resection for colon cancer between January 2000 and December 2007 were enrolled retrospectively. The rate of decrease was calculated using the following equation: ([preoperative CEA - postoperative CEA]/[preoperative CEA] ×100). RESULTS In the group with a preoperative serum CEA level of >5 ng/mL, the normalized group with a postoperative serum CEA level of ≤5 ng/mL showed a better overall survival (OS) rate and disease-free survival (DFS) rate than those of the non-normalized group (P ≤ 0.0001). The "cutoff values" of the rate of decrease in the perioperative serum CEA that determined the OS and the DFS were 48.9% and 50.8%, respectively. In the multivariate analysis of preoperative serum CEA levels >5 ng/mL, the prognostic factors for the OS and the DFS were the cutoff value (P < 0.0001) and the pN stage (P < 0.0001). CONCLUSION A rate of decrease of more than 50% in the perioperative serum CEA level, as well as the normalization of the postoperative serum CEA level, may be useful factors for determining a prognosis for colon cancer patients with high preoperative CEA levels.

Neuroendocrine carcinoma (NEC) is a rare tumor, comprising < 1% of stomach cancers. A 55-year-old woman was referred to our hospital with biopsy-proven gastric cancer. A shallow ulcerative lesion was detected in the lesser curvature of the lower body. It was suspected to be early gastric cancer IIA + IIC type. Thus, endoscopic submucosal dissection was performed. She was subsequently diagnosed with NEC, which is aggressive and carries a poor prognosis. We conducted a radical resection and a laparoscopic-assisted distal gastrectomy. The tumor had infiltrated the subserosal layer and 6/42 lymph nodes were involved. The mitotic index was 16/10 high power fields and the Ki-67 labeling index was 26%-50%. The final diagnosis of NEC was made according to the World Health Organization 2010 criteria. She was suspected of having jumping metastasis to the proximal margin. The patient was treated with an oral anticancer drug (5-flurouracil based drug) for 2 years. The patient has been followed up for 3 years without recurrence.