RESUMO
The structural and electronic properties of interfaces play an important role in the stability and functionality of solar cell devices. Experiments indicate that the SnO2/perovskite interfaces always show superior electron transport efficiency and high structural stability even though there exists a larger lattice mismatch. Aiming at solving the puzzles, we have performed density-functional theory calculations to investigate the electronic characteristics of the SnO2/perovskite interfaces with various stresses and defects. The results prove that the PbI2/SnO2 interfaces have better structural stability and superior characteristics for the electron transport. The tensile stress could move the conduction band minimum (CBM) of CH3NH3PbI3 upward, while the compressive stress could move the CBM of SnO2 downward. By taking into account the stress effect, the CBM offset is 0.07 eV at the PbI2/SnO2 interface and 0.28 eV at the MAI/SnO2 interface. Moreover, our calculations classify VI and Ii at the PbI2/SnO2 interface and Sn-I, Ii and Sni at the MAI/SnO2 interface as harmful defects. The Ii defects are the most easily formed harmful defects and should be avoided at both interfaces. The calculated results are in agreement with the available experimental observations. The present work provides a theoretical basis for improving the stability and photovoltaic performance of the perovskite solar cells.
RESUMO
A series of red-emitting Ca3ZrSi2O9:Eu3+,xBi3+ phosphors was synthesized using a conventional high temperature solid-state reaction method, for the purpose of promoting the emission efficiency of Eu3+ in a Ca3ZrSi2O9 host. The site preference of Bi3+ and Eu3+ in the Ca3ZrSi2O9 host was evaluated by formation energy. The effects of Bi3+ on electronic structure, luminescent properties, and related mechanisms were investigated. The inner quantum yield of the optimized sample increased to 72.9% (x = 0.08) from 34.6% (x = 0) at 300 nm ultraviolet light excitation. The optimized sample (x = 0.08) also showed excellent thermal stability, and typically, 84.2% of the initial emission intensity was maintained when the temperature increased to 150 °C from 25 °C, which is much higher than that without Bi3+ doping (70.1%). The mechanisms of emission properties and thermal stability enhancement, as well as the redshift of the charge transfer band (CTB) induced by Bi3+ doping in the Ca3ZrSi2O9:Eu3+ phosphor, were discussed. This study elucidates the photoluminescence properties of Bi3+-doped Ca3ZrSi2O9:Eu3+ phosphor, and indicates that it is a promising luminescent material that can be used in ultraviolet light-emitting diodes.
RESUMO
OBJECTIVE: To determine the hosts of hantavirus (HV) and its molecular epidemiological characteristics, to provide evidence for prevention and control on hemorrhagic fever with renal syndrome (HFRS). METHODS: Rodents were captured by a special trap within the residential area. The antigens of HV in lung tissues were detected by direct immuno-fluorescence assay (DFA). Nucleotide sequences of HV were amplified by RT-PCR with HV genotype-specific primer. The amplified genes were then sequenced. Phylogenetic tree were built on nucleotide sequence with ClustalX 1.83 software. RESULTS: 1421 rodents were captured and classified into 8 species of 4 Genera in the epidemic area within 10 counties of Chuxiong prefecture, Yunnan province, between 2005 and 2006. Out of the 1421 rodents, 1056 (74.31% ) of them were Rattus norvegicus and 280 (19.70%) belonged to Rattus flavipectus. The antigens of HV were detected by DFA in lung tissues and the total positive rate of HV was 5.15% (53/ 1029). After applying the sequencing nucleotide method to the 53 positive specimens, data showed that 21 specimens were positive and all of them belonged to Seoul type (15 samples were from Rattus norvegicus, 4 samples Rattus flavipectus, 2 samples Rattus nitidus). The partial S segments from 12 specimens were sequenced which appeared homologic with R22, L99 and HLD65 from GenBank in relatively high level (87.1% -99.7%). When compared to 76-118 strain of Hantaan type, their homologic degree was only 64.4%-69.1%. Results from Phylogenetic analysis showed that 12 specimens belonged to Seoul type. As for their homology, they were significantly similar to Seoul type and could be tentatively divided into two subtypes S1 and S3. CONCLUSION: It was confirmed that the Seoul type virus, as HFRS's pathogenetic agent mainly carried by rats, prevailed widely in Chuxiong prefecture. Owing to the local ecological environment, we also noticed the characteristics of different HV subtypes among Seoul type.
