Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit. However, it lacks a general strategy to control the precursor chemistry for defects density reduction in the family of iodine based perovskite. Here the alkaline environment in precursor solution is carefully investigated as an effective parameter to suppress the incident iodine and affects the crystallization kinetics during film fabrication, via rationale adjustment of the alkalinity of additives. Especially, a ‘residual free’ weak alkaline is proposed not only to shrink the bandgap of the absorber by modulating the stoichiometry of organic cation, but also to improve the open circuit voltage in the resultant device. Consequently, the certified efficiency of 20.87% (Newport) is achieved with one of the smallest voltage deficits of 413 mV in the planar heterojunction perovskite solar cell.

Background and Purpose-In 1960s, a stroke belt with high stroke mortality was discovered in the southeast UnitedStates. In China, where stroke is the leading cause of death, we aimed to determine whether a focal region of high stroke incidence (stroke belt) exits and, if so, the possible causal and modifiable factors. Methods-We systematically reviewed all studies of stroke incidence in China between 1980 and 2010, and included those which met our criteria for a high-quality study. Criteria for a provincial region of high stroke incidence were ranking in the top one third of all provinces for stroke incidence and ranking of more than one third of prefectural regions within the province in the top two sevenths of all prefectural regions for stroke incidence. We also reviewed regional distribution of major vascular risk factors, socioeconomic status, and demographic profiles in China. Results-Nine eligible studies provided data on the incidence of stroke in 32 of 34 provincial regions of China (with Hong Kong and Macao as exceptions) and 52% of the 347 prefectural regions. Nine provincial regions (Heilongjiang, Tibet, Jilin, Liaoning, Xinjiang, Hebei, Inner Mongolia, Beijing, and Ningxia) met our criteria for a region of high stroke incidence and constitute a stroke belt in north and west China. The incidence of stroke in the stroke belt was 236.2 per 100 000 population compared with 109.7 in regions outside the belt (rate ratio, 2.16; 95% confidence interval, 2.10-2.22).The mean population prevalence of hypertension and overweight (body mass index, >25) was greater in the stroke belt than that in other regions (15.3% versus 10.3%, P<0.001; 21.1% versus 12.3%, P=0.013, respectively). The prevalence of hypertension and overweight also correlated significantly with regional stroke incidence (R=0.642, P<0.001; R=0.438, P=0.014, respectively, by Spearman rank correlation). Conclusions-A stroke belt of high stroke incidence exists in 9 provincial regions of north and west China. The stroke belt may be caused, at least in part, by a higher population prevalence of hypertension and excess body weight. Lowering blood pressure and body weight in the stroke belt may reduce the geographic disparity in stroke risk and incidence in China.

In this population-based cross-national comparison, Han Chinese had a higher prevalence of confluent WMH than White Australians, but had a similar prevalence of lacunes and microbleeds.

The crystalline cooperativity of the donor and acceptor segment in double‐cable conjugated polymers plays an important role in the nanophase separation and photovoltaic performance in single‐component organic solar cells (SCOSCs). Two double‐cable conjugated polymers with the same conjugated backbone and perylene bisimide (PBI) side units were designed in which PBIs were positioned symmetrically and perpendicularly (P1) and asymmetrically and slantingly (P2) along the conjugated backbones. After thermal annealing, both conjugated backbones and PBI side units in P1 tend to form ordered nanostructures, while PBI side units in P2 dominated the crystallization and hamper the crystallization of conjugated backbones. P1 showed good crystalline cooperativity between conjugated backbones and PBI side units, resulting in improved power conversion efficiencies (PCEs) up to 3.43 % in SCOSCs, while P2 with poor crystalline cooperativity exhibited PCEs below 2.42 %.