Search

Vacancy related defects play a crucial role in optoelectronic properties and carrier transport for photovoltaic materials, especially for its structural evolution becoming non-radiative defects induced by strain. Thus far, the evolution phenomena of vacancy defects in halide perovskite triggered by energy or strain have not been systematically investigated. Herein, we study the change in defect levels occurred in different inorganic perovskite systems and the situation caused by strain in varied strength based on density functional theory calculations. We discover that VI deep levels are easily transformed from shallow levels due to the formation of Pb–Pb dimers and octahedral distortion in all-inorganic perovskites, especially in CsPbI3. Moreover, strain can be quantitatively applied to control the suppression or enhancement of the formation of dimer in CsBI3 (B = Pb/Ge) perovskites. Eventually, our calculation results unravel that the defect physics of VI defect and the formation mechanism of non-radiative center in all inorganic perovskites, which depends on the strain strength and the accompanying octahedral distortion. The strain modulation and its quantitation effect on defect evolution of dominant vacancy map a pioneering route toward fabricating high performance inorganic photovoltaics. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of layered α-MoO3 are greatly limited due to its wide band gap and low carrier concentration. The insertion of hydrogen (H) can effectively tune the band structure and carrier concentration of MoO3. Herein, first-principles calculations were performed to unravel the physical mechanism of a H-doped α-MoO3 system. We found that the modulation of the electronic structure of H-doped MoO3 depends on the doping concentration and position of the H atoms. It was found that the band gap decreases at 8% doping concentration due to the strong coupling between Mo-4d and O-2p orbits when H atoms are inserted into the interlayer. More interestingly, the band gap decreases to an extreme due to the Mo-4d orbit when all the H atoms are inserted into the intralayer only, which has a remarkable effect on light absorption. Our research provides a comprehensive theoretical discussion on the mechanism of H-doped α-MoO3 from the doping positions and doping concentrations, and offers useful strategies on doping modulation of the photoelectric properties of layered transition metal oxides. [ABSTRACT FROM AUTHOR]

The archaeological culture found in Xiaohe Cemetery (1980-1450 BC) is one of the early Bronze Age cultures in Xinjiang, northwestern China. The material assemblages from Xiaohe culture display features with both eastern and western influences. These east-west cultural and dietary interactions may be observed via the diet of the Xiaohe population. This paper examined the stable carbon and nitrogen isotopes of human and animal bones and human hairs from the Xiaohe Cemetery and compared with those of human bones from the Gumugou Cemetery, another Xiaohe culture site. The results indicate that the diets of the peoples from the Xiaohe culture varied significantly over different periods. The unified diets of the earlier periods reflect that an admixed population first settled in the Lop Nur region and primarily engaged in animal husbandry. In the later periods, the transformations in the human diets in this region reflect that new immigrants constantly relocated here and promoted population complexity over time. Moreover, this population occasionally produced small quantities of domesticated wheat and millet. The complex population and diversified economy of the Xiaohe culture were due to the expansion of the coeval cultures in the Eurasian steppe and eastern immigrants. Additionally, the millet cereal was probably mainly used for ritual practices rather than for staple food in the later periods. [ABSTRACT FROM AUTHOR]

Sn-Ge mixed perovskites have been proposed as promising lead-free candidates in the photovoltaics (PV) field. In this work, we discovered a stable P 1 phase Sn-Ge mixed structure (CsSn 0.5 Ge 0.5 I 3 ) with an appropriate band gap value of 1.19 eV, which manifests its unique structural stability and physics properties. The thermodynamic stability of this mixed structure under different growth conditions and all possible native defects are depicted in detail. The formation energies and dominant native point defects indicate that P 1 phase CsSn 0.5 Ge 0.5 I 3 exhibits unipolar self-doping behavior (p-type conductivity) and good defect tolerance while the growth condition changes. In addition, the calculation of light absorption confirmed that the P 1 phase has a higher light absorption coefficient than that of MAPbI 3 in the visible light range, showing excellent light absorption. Our work not only provides theoretical guidance for unraveling the unusual structural stability of Sn-Ge mixed perovskites, but also offers a useful scheme to modulate the stability and optoelectronic properties of Ge-based perovskites through alloy engineering.

Objective: To observe the effects of electroacupuncture (EA) on body weight, insulin resistance (IR) and hypothalamic insulin signal molecule in rats with diet-induced obesity (DIO), and to explore the action mechanism of EA on DIO., Methods: Fifty SD male rats were randomly divided into a low fat diet (LFD) group (10 rats) and a high fat diet (HFD) group (40 rats). Rats were fed with LFD and HFD, respectively, and the DIO model was established in the HFD group. After the model was established, the rats were randomly divided intoa model group, an EA group and a medication group, ten rats in each one. The rats in the EA group were treated with EA at "Housanli" (ST 36) and "Quchi" (LI 11) for 20 min, once a day for totally 28 days. The rats in the medication group were treated with intragastric administration of orlistat, once a day for 28 days. The rats in the LFD group and model group received no treatment. After treatment, HE staining method was applied to observe the morphological changes of liver; the biochemistry technique and radioimmunoassay method were applied to detect the fasting plasma glucose (FPG) and fasting insulin (FINS); Western blot method was applied to measure the expression of phosphatidylinositol-3 kinase p85 subunit (PI3K-p85) and insulin receptor substrate 2 (IRS2)., Results: Under light microscope, compared with the model group, the fatty degenerative cells were below 1/2 in the EA group and the medication group, accompanied with decreased lipid droplet, mild edema and none inflammatory infiltration. The body weight, FPG, FINS, homeostasis model assessment-insulin resistance index (HOMA-IR) and PI3K-p85 in the EA group were significantly lower than those in the model group ( P <0.01, P <0.05), but the expression of IRS2 was not significantly different from the model group ( P >0.05). The body weight, HOMA-IR and PI3K-p85 in the medication group were lower than those in the model group ( P <0.01, P <0.05), but the expression of IRS2 was higher than that in the model group ( P <0.05). The differences of each index were not significant between the EA group and the medication group (all P >0.05). In addition, rats in the medication group showed watery defecation, decreased activity, fatigue mentality and yellow hairs, while rats in the EA group showed normal defecation and vivid hair., Conclusions: EA can decrease the expression of PI3K-p85 to prompt the IR of DIO rats, inhibit the weight body and improve hepatic steatosis, which is probably one of the action mechanisms of EA on DIO. Besides, the adverse effects as the medication group can be avoided.