The formation age and evolution of Kumtagh Desert

The ancient aeolian sand has been regarded as an indicator for the formation and evolution of a desert in the past.Kumtagh Desert is located at the northern fringe of Qinghai-Tibet Plateau.The first integrated scientific investigation to the desert was carried out during the period of 2004-2006.Kumtagh Desert is an ideal natural model for studying the formation and evolution of the desert because the Quaternary strata containing ancient aeolian sands are widely distributed.The integrated field investigation and studies on sedimentary,chronology and palynology of typical profiles named Suosuo gully,Xiaoquan gully and gravel body with ancient aeolian sand layers showed that Kumtagh Desert was probably formed as early as 2,097.7±314.7 ka BP.During the period of 386.9±58.0 ka BP to 285.9±42.9 ka BP,the desert largely expanded and formed its modern distribution pattern.The desert was originally developed in the southwest,subsequently,expanded to the north and northeast.The sedimentary facies of Suosuo gully profile revealed that the desert experienced at least 19 cycles of advance and inverse processes of desertification with an average period of 110 ka in the Quaternary.The neotectonic movements played an important role in the formation,development and geomorphology of the desert.On one hand,the movements caused the formation of intermontane fault basin,which was further developed towards the closed drought basin,and caused the formation of natural environment.On the other hand,under the control of surrounding faults,the unique broom-shaped desert landscape was formed,and the gullies and sand ridges in this region experienced an abrupt directional change from north by west to north by east at the location of 39°45＇-39°55＇N.The unique landscape of gravel body that occurred widely in the northern desert was formed after 285.9±42.9 ka BP.The results in this paper provide the scientific basis for studying the formation age and evolutionary process under the dry climate and environment in the northwestern China,and the uplifting of Qinghai-Tibet Plateau as well as its responses to the global climate changes.

Shiyang River ecosystem problems and countermeasures

With the increase of population and the development of social economy, contradiction between water supply and demand of Shiyang River Basin become more outstanding. Unreasonable exploitation and utilization of water resources cause the serious deterioration of ecological environment. According to the present ecoligical situation, by analyzing some actual problems of the ecosystem of Shiyang River Basin, a series of feasible control countermeasures are proposed. The article provide theoretical basis for the treatment and recovery of the degradation of ecological environment of Shiyang Rive Basin.

Constructing low-dimensional perovskite network to assist efficient and stable perovskite solar cells

The use of low-dimensional(LD)perovskite materials is crucial for achieving high-performance perovskite solar cells(PSCs).However,LD perovskite films fabricated by conventional approaches give rise to full coverage of the underlying 3D perovskite films,which inevitably hinders the transport of charge carriers at the interface of PSCs.Here,we designed and fabricated LD perovskite structure that forms net-like morphology on top of the underlying three-dimensional(3D)perovskite bulk film.The net-like LD perovskite not only reduced the surface defects of 3D perovskite film,but also provided channels for the vertical transport of charge carriers,effectively enhancing the interfacial charge transfer at the LD/3D hetero-interface.The net-like morphological design comprising LD perovskite effectively resolves the contradiction between interfacial defect passivation and carrier extraction across the hetero-interfaces.Furthermore,the net-like LD perovskite morphology can enhance the stability of the underlying 3D perovskite film,which is attributed to the hydrophobic nature of LD perovskite.As a result,the net-like LD perovskite film morphology assists PSCs in achieving an excellent power conversion efficiency of up to 24.6%with over 1000 h long-term operational stability.

CsPbI_(3)太阳电池采用蒸镀法实现超过16%的电池效率

近年来全无机钙钛矿Cs PbI_(3)由于其优异光、热稳定性、理想的带隙宽度(1.73 eV,叠层太阳电池顶部电池的理想吸光材料)等受到了极大关注.然而,黑相Cs PbI_(3)在室温下极易发生相变,导致其能量转换效率大幅下降.大量研究已经证实传统溶液法制备的黑相Cs Pb I_(3)钙钛矿薄膜会不可避免地引入有机组分,这为探究纯无机Cs Pb I_(3)本征物理性质及光电性能带来严重挑战.本文延续了前期气相沉积制备杂化钙钛矿薄膜的工作,利用双源气相沉积技术共蒸Pb I2和Cs I,制备出高质量的纯无机黑相Cs Pb I_(3)薄膜.作者结合高通量实验和气氛退火工艺,优化了全无机Cs Pb I_(3)化学计量比,并有效降低了薄膜缺陷态密度,实现电池效率大于16%,这是目前气相沉积纯无机Cs Pb I_(3)获得的最高效率.同时,该工作详细阐明了Cs Pb I_(3)薄膜中化学计量比、退火气氛及器件光电性能之间的密切联系,为进一步实现高效稳定纯无机Cs Pb I_(3)电池提供了方向指引.