Ethanol purification enables high-quality α-phase FAPbI3 perovskite microcrystals for commercial photovoltaic applications.

Reliable quality and sustainable processes must be developed for commodities to enter the commercial stage. For next-generation photovoltaic applications such as perovskite solar cells, it is essential to manufacture high-quality photoactive perovskites via eco-friendly processes. We demonstrate that ethanol, an ideal green solvent, can be applied to yield efficient alpha-phase FAPbI3 perovskite microcrystals.

Controlled growth of perovskite layers with volatile alkylammonium chlorides.

Controlling the crystallinity and surface morphology of perovskite layers by methods such as solvent engineering1,2 and methylammonium chloride addition3-7 is an effective strategy for achieving high-efficiency perovskite solar cells. In particular, it is essential to deposit α-formamidinium lead iodide (FAPbI3) perovskite thin films with few defects due to their excellent crystallinity and large grain size. Here we report the controlled crystallization of perovskite thin films with the combination of alkylammonium chlorides (RACl) added to FAPbI3. The δ-phase to α-phase transition of FAPbI3 and the crystallization process and surface morphology of the perovskite thin films coated with RACl under various conditions were investigated through in situ grazing-incidence wide-angle X-ray diffraction and scanning electron microscopy. RACl added to the precursor solution was believed to be easily volatilized during coating and annealing owing to dissociation into RA0 and HCl with deprotonation of RA+ induced by RA⋯H+-Cl- binding to PbI2 in FAPbI3. Thus, the type and amount of RACl determined the δ-phase to α-phase transition rate, crystallinity, preferred orientation and surface morphology of the final α-FAPbI3. The resulting perovskite thin layers facilitated the fabrication of perovskite solar cells with a power-conversion efficiency of 26.08% (certified 25.73%) under standard illumination.

[Clinical features of acute hepatitis A in recent two years].

BACKGROUND/AIMS: The purpose of this study was to characterize the clinical features of acute hepatitis A in Seoul and Gyeonggi province during the recent 2 years. METHODS: We reviewed the medical records of 222 patients who were diagnosed as acute hepatitis A between August 2005 and March 2007 at the Konkuk University Hospital and Korea University, Ansan Hospital. The clinical manifestation, serological tests, and image findings were analyzed. RESULTS: Median age of the patients was 28.1 years and the age groups of highest incidence were the second and third decade. The frequent symptoms were anorexia (66.4%), fatigue (49.2%), fever (47.7%), and abdominal discomfort (42.5%). Fourteen cases (6.3%) showed renal insufficiency, and hemodialysis was performed in one. Cholestatic hepatitis in 2 cases, relapsing hepatitis in 4 cases and prolonged hepatitis in 13 cases were observed. However, there was no case of fulminant hepatitis or death. The underlying diseases including chronic hepatitis B, diabetes mellitus and thyroid disorder did not affect the disease severity of hepatitis A. IgM anti-HAV was not detected initially in 6.7% of the patients. Anti-HEV (IgM) was detected simultaneously in 3 of 150 patients. CONCLUSIONS: The age of patients with acute hepatitis A has been increased in the recent years. Most patients recovered uneventfully. However, unusual patterns of severe hepatitis and renal insufficiency occurred in considerable number of cases. Follow-up serologic test for IgM anti-HAV is needed in seronegative cases with hepatitis A.