Rational molecular engineering towards efficient heterojunction solar cells based on organic molecular acceptors

The selection of photoactive layer materials for organic solar cells(OSCs) is essential for the photoelectric conversion process.It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis.However,there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions.Therefore in this study we utilize a chlorophyll derivative,Ce_(6)Me_(3),as a donor material and investigate the performance of its heterojunction with acceptor materials.Through density functional theory,the photoelectric performances of acceptors,i ncluding the fullerene derivative PC_(71)BM and the terminal halogenated non-fullerene DTBCIC series,are compared in detail.It is found that DTBCIC-C1 has better planarity,light absorption,electron affinity,charge reorganization energy and charge mobility than others.Ce_(6)Me_(3) has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties.Furthermore,the designed Ce_(6)Me_(3)/DTBCIC interfaces have improved charge separation and reorganization rates(K_(CS)/K_(CR)) compared with the Ce_(6)Me_(3)/PC_(71)BM interface.This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs.

Does bicarbonate affect the nitrate utilization and photosynthesis of Orychophragmus violaceus?

The effect of bicarbonate(HCO_3^-) on the growth and development of plants varies by species. To better understand inorganic carbon and nitrogen assimilation changes of karst-adaptable plants under different HCO_3^- treatments, we conducted experiments on seedlings and in vitro plantlets of Orychophragmus violaceus(Ov).We found that the vital photosynthesis potential(as measured by net photosynthetic rate, actual photochemical efficiency of photosystem-II, photochemical quenching coefficient, and the instantaneous carbon isotope ratio of3-phosphoglycerate) was consistent under different HCO_3^- treatments of Ov. Bicarbonate's lack of effect on carbon assimilation of Ov may be related to carbonic anhydrase in Ov converting HCO_3^- to H2 O and CO2. In this way, Ov could prevent HCO_3^- ion toxicity and high pH from harming its growth and development under HCO_3^- stress.This study also found that high HCO_3^- concentrations could promote nitrogen assimilation and utilization of Ov through changes in related indexes(foliar nitrogen isotope fractionation ratio, stable nitrogen isotope assimilation ratio, foliar stable nitrogen isotope fractionation, nitrate nitrogen utilization efficiency, and nitrate utilization share)under different HCO_3^- treatments. Bicarbonate has different effects on photosynthesis and on inorganic nitrogen assimilation of Ov, which may be connected tophotosynthesis providing electrons for nitrate/nitrite reduction through the photosynthetic chain.

The δ^15N response and nitrate assimilation of Orychophragmus violaceus and Brassica napus plantlets in vitro during the multiplication stage cultured under different nitrate concentrations

Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of inorganic nitrogen. However, the foliar δ^(15)N of intact plants, which is a consequence of nitrate assimilation occurring in the roots and shoots, is not suited for studying nitrate assimilation in cases where nitrate is the sole nitrogen source. In this study, Orychophragmus violaceus(Ov) and Brassica napus(Bn) plantlets, in which nitrate assimilation occurred in the leaves, were used to study the relationship between foliar δ^(15)N and nitrate assimilation.The plantlets were grown in vitro in culture media with different nitrate concentrations, and no root formation occurred for the plantlets during the multiplication stage.Nitrogen isotope fractionation occurred in both the Ov and the Bn plantlets under all treatments. Furthermore, the foliar nitrogen content of both the Ov and Bn plantlets increased with increasing nitrate concentration. Foliar nitrogen isotope fractionation was negatively correlated with foliar nitrogen content for both the Ov and Bn plantlets. Our results suggest that the foliar nitrogen isotope fractionation value could be employed to evaluate nitrate assimilation ability and leaf nitrate reductase activity.Moreover, high external nitrate concentrations couldcontribute to improved foliar nitrogen content and enhanced nitrate assimilation ability.

铋基有机金属框架衍生的棒状纳米反应器用于中性水系电池型负极

氧化铋(Bi_(2)O_(3))因其理论容量高与工作电位窗口宽而成为具有应用前景的电池型负极材料.但是,氧化铋缓慢的反应动力学与较差的循环寿命限制了其在实际器件中的应用.在本文中,我们以铋基金属有机框架(CAU-17)作为前驱体与模板,通过热解法结合氧化态调节制备了一种封装在棒状多孔碳纳米反应器中的Bi-Bi_(2)O_(3)纳米颗粒(Bi-Bi_(2)O_(3)@CNR).该电池型负极在硫酸钠溶液中表现出良好的导电性、快速的反应动力学、高的容量与长的循环寿命.实验结果与密度泛函理论计算表明,金属有机框架衍生的多孔碳基质与引入氧化铋晶格中的金属铋能够进一步提升氧化铋的电化学性能.基于Bi-Bi_(2)O_(3)@CNR负极和δ-MnO_(2)正极的中性水系钠离子电池电容混合器件可以同时实现高能量和高功率密度,同时具有2.4 V的超宽电位窗口.本文通过设计高稳定性和反应动力学有利的主体结构及调节活性成分的氧化态,为开发可用于中性水系电池型负极的高性能氧化铋基电极提供了新的策略.

基于深度学习的多方对话研究综述

近年来,随着深度学习技术的广泛应用,人机对话研究取得了突破性进展.但是,目前的人机对话系统大多是在人机双方参与的假设下进行设计的,而更具挑战性的人机多方对话的研究和应用尚不成熟.本文将立足于自然语言处理领域,对近几年基于深度学习的多方对话研究进展进行综述.首先从人机对话角度出发,整理多方对话系统的关键问题和已有解决方案;然后,梳理基于多方对话的其他自然语言处理任务;之后,总结已有多方对话研究的数据集,并分析现有数据集的局限性和改进方案;最后,展望多方对话研究的未来发展趋势.