Oriented Crystal Growth during Perovskite Surface Reconstruction.

Surface passivation has become a key strategy for an improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) since PSCs experienced a steep increase in PCE and reached a comparably matured point. Recently, surface passivation using a mixed salt of fluorinated alkyl ammonium iodide and formamidinium bromide demonstrated a remarkable improvement in both performance and stability, which can be tuned by the length of the alkyl chain. Nevertheless, the role of the alkyl chain in manipulating surface-limited crystal growth was not fully understood, preventing a further progress in interface control. In this study, we found that the length of the fluorine-substituted alkyl chain governed the crystal formation dynamics by manipulating surface tensions of different crystal orientations. The overall enhancement of the (001) plane, being the most favored, commonly resulted from the surface reformation of the perovskite film regardless of the chain length, while the highly oriented (001) over (111) was monitored with a particular chain length. The enhanced crystal orientation during surface recrystallization was responsible for the low trap density and thus effectively suppressed charge recombination at the interface, resulting in a considerable increase in open-circuit voltage and fill factor.

Selection of a Suitable Solvent Additive for 2-Methoxyethanol-Based Antisolvent-Free Perovskite Film Fabrication.

In this study, we compare various solvents with different Gutmann donor numbers as additives to improve the quality of perovskite films via an antisolvent-free process, using 2-methoxyethanol (2MOE) as the solvent. In 2MOE-based solutions, we found that the higher the donor number of the solvent, the lower the amount of the solvent required to form insoluble adducts. Furthermore, we found that N-methyl-2-pyrrolidone (NMP), which has a relatively low donor number and vapor pressure, can be added without a limitation to precipitation, while the degree of the intermediate phase in the as-deposited film is controlled by the amount of NMP added. We obtained pinhole-free and planar perovskite films by optimizing the amount of NMP added and fabricated devices based on NMP-assisted MAPbI3 and MAPbI3-xClx films, with efficiencies of 18.80 and 20.39%, respectively.

Influence of metallization process on solution-processed InGaZnO thin film transistors.

Low-temperature solution-processed InGaZnO (IGZO) thin film transistors (TFTs) have recently attracted significant attention as the next-generation flexible display TFTs, owing to their high transparency, high electrical performance, low-cost fabrication, and large-area scalability. However, solution-processed amorphous IGZO TFTs have several drawbacks, such as poor film quality or low stability, and have been studied with view to improving the device performance. One of the critical components determining device characteristics is the metallization process, which we systematically studied using aluminum (Al) source and drain electrodes. The electrical properties were measured for different channel lengths and evaluated using the threshold voltage (Vth) and subthreshold swing (SS). Al electrodes directly affect the channel region, enhancing the electron density because of the doping effect from Al and oxygen vacancy-related oxidation of Al and causing an abnormal negative shift ofVth, which is confirmed by the component analysis via various spectroscopies. To understand and improve the TFT characteristics, we conducted a low-temperature post-annealing process and polymer passivation and succeeded in movingVthfrom over 150 V to near 0 V and remarkably improved SS. This study discovered that the influence of source-drain metallization on the channel region determines the device characteristics through the close relation between metal oxidation and the number of oxygen vacancies.

Manipulating the crystal structure of a conjugated polymer for efficient sequentially processed organic solar cells.

Recently, the sequential (Sq) process, which forms nanoscale network structures from quasi-solid-state inter-diffusion through swelling and annealing, is considered to be one of the most efficient methods for fabricating organic solar cells and blend films. Here, we examined the effect of the crystallinity and orientation of poly(3-hexylthiophene) (P3HT) molecules on the formation of the nanostructure by carrying out a Sq process using various solvents with different boiling points. We showed that the moderate crystallinity promoted suitable inter-diffusion between the donor (P3HT) and acceptor ([6,6]-pentadeuterophenyl C61 butyric acid methyl ester, PC60BM), and hence was important for achieving high-performance solar cells using Sq processing. Nanostructure formation by inter-diffusion was investigated and visualized by taking a combination of grazing-incidence wide-angle X-ray scattering (GIWAXS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements. In addition, our Sq-processed solar cell yielded a device efficiency as high as 3.25%, and was also impressive because it was made with an eco-friendly solvent and using a short-duration annealing process, in contrast to the conventional BHJ process. The present findings provided advanced insight into the Sq process, and we anticipate this efficacious sequential process to contribute not only to the development of higher-efficiency organic solar cells but also to the fabrication of functional blend films.

The Prevalence of Chronic Physical Diseases Comorbid with Depression among Different Sex and Age Groups in South Korea: A Population-Based Study, 2007-2014.

OBJECTIVE: People with depression often suffer from comorbid, chronic physical diseases. Little is known about how demographic characteristics such as age and sex influence the prevalence of chronic physical diseases comorbid with depression. Therefore, this study aimed to explore the age and sex differences in the prevalence of diverse, chronic physical diseases comorbid with depression. METHODS: This cross-sectional survey were conducted with the participants (n=45,598) of the Korean National Health and Nutrition Examination Survey (KNHANES). Using log-binomial regression, age adjusted prevalence ratios (APR) of chronic physical diseases of participants with depression and those without depression were estimated for each sex and age group. RESULTS: The APR of most chronic physical diseases were significantly higher among respondents with depression than those without depression. Chronic physical diseases that showed the highest APR were asthma in adult male respondents (APR=3.46) and adult female respondents (APR=2.19) and chronic renal failure in elderly male respondents (APR=8.36) and elderly female respondents (APR=1.94). CONCLUSION: Prevalence ratios of the chronic physical diseases comorbid with depression differed according to sex and age groups. Collaborative care strategies should be designed according to demographic characteristics of the population.

Association between Healthcare Utilization and Depression in Korean Women with Cardiovascular Conditions.

OBJECTIVE: This study aimed to examine the associations between depression and both coronary artery disease (CAD) and cardiovascular risk factors (CVRs) in Korean women. Furthermore, this study sought to determine whether depression was associated with use of healthcare services in women with CAD or CVRs. METHODS: This cross-sectional study was conducted on 26,335 women who were aged 19 years or older, and who participated in the Korean National Health and Nutrition Examination Survey (2007-2014). Associations of prior diagnosis of depression with CAD and CVRs and with nonutilization of healthcare services were investigated. RESULTS: Women with depression had a higher prevalence of CAD and CVRs including obesity, hypertension, dyslipidemia, and metabolic syndrome than those without depression. In addition, depression was significantly associated with nonutilization of healthcare services in women with most CVRs. CONCLUSION: Considering the high rate of comorbid depression with CAD or CVRs and the low lvels of health service utilization in depressed patients, screening for common CVRs, such as obesity, hypertension, and dyslipidemia, should be provided for patients with depression in mental health care settings.