30 research outputs found
Identification of Free and Bound Exciton States and Their Phase-Dependent Trapping Behavior in Lead Halide Perovskites
In this work we probe the sub-gap energy states within polycrystalline and
single crystal lead halide perovskites to better understand their intrinsic
photophysics behaviors. Through combined temperature and intensity-dependent
optical measurements, we reveal the existence of both free and bound exciton
contributions within the sub-gap energy state manifold. The trapping and
recombination dynamics of these excitons is shown to be strongly dependent on
the structural phase of the perovskite. The orthorhombic phase exhibits
ultrafast exciton trapping and distinct trap emission, while the tetragonal
phase gives low monomolecular recombination velocity and capture cross-sections
(~10-18 cm2). Within the multiphonon transition scenario, this suppression in
charge trapping is caused by the increase in the charge capture activation
energy due to the reduction in electron-lattice interactions, which can be the
origin for the unexpected long carrier lifetime in these material systems.Comment: 5 figure
The microbiota continuum along the female reproductive tract and its relation to uterine-related diseases
Reports on bacteria detected in maternal fluids during pregnancy are typically associated with adverse consequences, and whether the female reproductive tract harbours distinct microbial communities beyond the vagina has been a matter of debate. Here we systematically sample the microbiota within the female reproductive tract in 110 women of reproductive age, and examine the nature of colonisation by 16S rRNA gene amplicon sequencing and cultivation. We find distinct microbial communities in cervical canal, uterus, fallopian tubes and peritoneal fluid, differing from that of the vagina. The results reflect a microbiota continuum along the female reproductive tract, indicative of a non-sterile environment. We also identify microbial taxa and potential functions that correlate with the menstrual cycle or are over-represented in subjects with adenomyosis or infertility due to endometriosis. The study provides insight into the nature of the vagino-uterine microbiome, and suggests that surveying the vaginal or cervical microbiota might be useful for detection of common diseases in the upper reproductive tract.Shenzhen Municipal Government of China [JCYJ20160229172757249, JCYJ20150601090833370]; Danish Strategic Research Council [2106-07-0021]; Ole Romer grant from Danish Natural Science Research Council; Solexa project [272-07-0196]SCI(E)ARTICLE
Opto-electro-modulated transient photovoltage and photocurrent system for investigation of charge transport and recombination in solar cells
Heterojunction interface regulation to realize high-performance flexible Kesterite solar cells
Flexible Cu2ZnSn(S, Se)4 (CZTSSe) solar cells take the advantages of
environmental friendliness, low cost, and multi-scenario applications, and have
drawn extensive attention in recent years. Compared with rigid devices, the
lack of alkali metal elements in the flexible substrate is the main factor
limiting the performance of flexible CZTSSe solar cells. This work proposes a
Rb ion additive strategy to simultaneously regulate the CZTSSe film surface
properties and the CdS chemical bath deposition (CBD) processes. Material and
chemical characterization reveals that Rb ions can passivate the detrimental
Se0 cluster defect and additionally provide a more active surface for the CdS
epitaxial growth. Furthermore, Rb can also coordinate with thiourea (TU) in the
CBD solution and improve the ion-by-ion deposition of the CdS layer. Finally,
the flexible CZTSSe cell fabricated by this strategy has reached a high
total-area efficiency of 12.63% (active-area efficiency of 13.2%), with its VOC
and FF reaching 538 mV and 0.70, respectively. This work enriches the alkali
metal passivation strategies and provides new ideas for further improving
flexible CZTSSe solar cells in the future