Stabilizing high-efficiency perovskite solar cells (PSCs) at operating conditions remains an unresolved issue hampering its large-scale commercial deployment. Here, we report a star-shaped polymer to improve charge transport and inhibit ion migration at the perovskite interface. The incorporation of multiple chemical anchor sites in the star-shaped polymer branches strongly controls the crystallization of perovskite film with lower trap density and higher carrier mobility and thus inhibits the nonradiative recombination and reduces the charge-transport loss. Consequently, the modified inverted PSCs show an optimal power conversion efficiency of 22.1% and a very high fill factor (FF) of 0.862, corresponding to 95.4% of the Shockley-Queisser limited FF (0.904) of PSCs with a 1.59-eV bandgap. The modified devices exhibit excellent long-term operational and thermal stability at the maximum power point for 1000 hours at 45°C under continuous one-sun illumination without any significant loss of efficiency.

Four recent reanalyses—the 55-yr Japanese Reanalysis Project (JRA-55), Interim ECWMF Re-Analysis (ERA-I), NCEP Climate Forecast System Reanalysis (CFSR), and NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA)—are assessed to clarify their quality in representing the diurnal cycle over East Asia. They are found to present similar patterns/structure and summer progress of the mean wind diurnal cycle, whereas they exhibit some differences in diurnal amplitude, particularly for the low-level meridional wind. An evaluation with intense soundings suggests that the amplitude difference mainly results from the diurnal variation of mean bias that differs among reanalyses. The root-mean-square (RMS) error is found to have a diurnal variation more evident in CFSR and MERRA than that in JRA-55 and ERA-I, which strongly affects the representation of the varying diurnal amplitude at the peak hours of RMS error. Compared with satellite-derived rainfall, the four reanalyses are shown to reproduce well the rainfall diurnal cycle over East Asia in terms of large-scale terrain contrast, summer progress, and interannual variability. JRA-55 even presents a long-term increase of morning rainfall percentage over the east China plain over the past four decades, consistent with rain gauge observations. The four reanalyses exhibit some considerable discrepancies at regional scale; JRA-55 gives the best capture of the rainfall diurnal cycle over the Tibetan Plateau and the eastward propagation to the eastern lees. These results suggest that new reanalyses are potentially applicable for studying the large-scale diurnal variability over East Asia, whereas their different preferences, especially at regional scale, should be of concern in data application.

[1] Using the satellite data, spatial patterns of precipitation diurnal cycles and their seasonality were examined with emphasis on southeastern China (SEC). Results show that spatial distributions of diurnal cycles over SEC have a robust large-scale seasonality in which the regional differences are evidently embedded. Rainfall diurnal variability is weak in spring but it becomes more pronounced from presummer. Both the mean rain rates and amplitudes of diurnal cycles experience remarkable amplification during presummer. The widespread and strong morning rainfall dominates the SEC area, especially inland valleys and plains, and offshore areas. The morning peak rainfall over western SEC is largely contributed by the increasing rain frequency and diurnally varying intense rain rates. Even over eastern SEC, morning rainfall still has a comparable magnitude to afternoon rainfall. In contrast, spatial distributions of diurnal cycles in midsummer are dependent primarily on topography. The morning (afternoon) rainfall is mainly located over valleys, basins, and oceans (plateaus and mountains). The afternoon peak rainfall becomes a notable feature over southern China. The signature of widespread morning rainfall decays during midsummer and remains apparent only in central eastern China, which is likely related to the north shift of summer rainband.

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