Development of hole transport materials (HTMs) with comprehensive passivation effects and appropriate energy levels are urgently desirable for constructing highly efficient and stable perovskite solar cells (PSCs). Herein, we report an effective interfacial molecular doping strategy and energy level regulation approach to improve the performance of PSCs with ultrasimple carbazole-based HTMs CZ-As and CZ-Py. The pyridine-substituted HTM CZ-Py exhibits a stepped energy level with perovskite and CZ-As, effective passivation of Pb2+ defect, as well as the assistance of the formation of high-quality perovskite film and hole transport layer (HTL). By utilizing CZ-Py as interfacial doping material and CZ-As as HTM, the undesired charge carrier recombination at the perovskite/HTM interface are significantly restricted. Finally, the fabricated PSCs feature an impressive power conversion efficiency (PCE) up to 23.5% and good long-term stability. This work demonstrates a facile and highly efficient way to reduce nonradiative recombination and further improve photovoltaic performance of PSCs.

Chemical additive engineering is reported to be a simple yet effective approach to passivate shallow defects at the surface and grain boundaries, restrict nonradiative recombination losses, and further enhance the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, we successfully introduce a small organic molecule 3,5-bis(trifluoromethyl)benzoic acid (6FBzA) into an antisolvent as a shallow defect passivator for perovskite films. The Pb 2+ defects at the surface are greatly healed due to the coordination interaction of carbonyl and fluorine groups of 6FBzA with Pb 2+ . Consequently, the trap-assisted nonradiative recombination is effectively suppressed, as well as the interfacial charge extraction and transfer is significantly enhanced. As a result, the 6FBzA-treated PSC obtains a champion PCE of 21.09% with negligible hysteresis, which is obviously superior to the reference device (18.45%). Furthermore, on account of the high hydrophobicity of 6FBzA, the unencapsulated 6FBzA-treated device exhibits a good long-term stability, maintaining 82% of its initial PCE at a relative humidity of 30−40% in ambient air after 1800 h of aging.

No abstract

BackgroundMost studies on diabetes prevalence and awareness in China are regional or about a single province, and differences between coastal and interior provinces have not been discussed even in the nation-based studies. The aim of this study was to determine regional differences in diabetes prevalence and awareness between coastal and interior provinces, and to identify the factors associated with diabetes prevalence and awareness.MethodsProvinces Fujian and Shaanxi were chosen to represent the coastal and interior provinces, respectively. The data of two provinces were from the China National Diabetes and Metabolic Disorders Study 2007–08. A total of 5926 people (Fujian 2672 and Shaanxi 3254) aged above 20 years were included as participants in the study. Age-standardized prevalence and awareness were compared between provinces. Logistic regression analysis was performed not only to examine risk factors of diabetes prevalence and awareness, but also to examine the association between regional difference and diabetes prevalence and awareness.ResultsThe age-standardized prevalence of diabetes in Fujian was higher than that in Shaanxi among total (11.5% vs. 8.0%), male (13.6% vs. 8.9%) and female (10.8% vs. 7.4%) populations. Diabetes awareness for total and male population in Fujian was higher than that in Shaanxi (42.3% vs. 34.9% and 46.8% vs. 35.2%, respectively). Age, sex, central obesity, family history of diabetes, and metabolic risk factors were all significantly associated with diabetes prevalence in both provinces. However, cigarette smoking was significantly associated with prevalence in Fujian and physical activity was significantly associated with the prevalence in Shaanxi. Family history of diabetes was the only independent risk factor of diabetes awareness in both provinces. After being adjusted for all listed risk factors, the regional difference of diabetes prevalence was still significant, but that of diabetes awareness lost significance.ConclusionsBoth diabetes prevalence and awareness were higher in coastal provinces and lower in interior provinces in China. Lifestyle risk factors were found to contribute differently to diabetes prevalence in the two provinces and other unknown risk factors may account for differences of diabetes prevalence between provinces. In addition, family history of diabetes was the only independent risk factor in both provinces.

New types of synthetic municipal solid wastes (MSWs) were developed, exhibiting engineering characteristics similar to those of real MSWs at different states of degradation in terms of total unit weight, void ratio, water content, compressibility, permeability, stress-strain relationship, and shear strength. Using these synthetic MSWs, several centrifuge model tests on the stability of geosynthetics-lined landfills with rising water levels were performed. The test results revealed the developing processes of MSW landfill failures induced by rising water levels. In most tests, a continuous slide occurred once a critical water level was attained. The ratio of critical water level and landfill height was 0.75-0.92 for present model tests using fresh or partly degraded synthetic MSWs with landfill slope ratio of 1:1-1:3, increasing with the increases of MSW degradation states and decreases of the slope ratio. An engineered berm increased the critical water level by 1.3%-9.5%. The landfills without an engineered berm tended to slide along the bottom liner; however, for normal landfills with an engineered berm and a slope ratio of 1:3, penetrating cracks developed when the failures occurred. These results provide a good reference for water level and stability control of the landfill, and the construction of an engineered berm is suggested to improve the stability of these landfills. Mots-clés : déchets municipaux solides, décharges de déchets, essais sur modèle centrifuge, niveau d'eau critique, rupture de pente.