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Xujie Lü Constantinos Stoumpos Qingyang Hu Xuedan Ma Dongzhou Zhang Songhao Guo Justin Hoffman Kejun Bu Xiaofeng Guo Yingqi Wang Cheng Ji Haijie Chen Hongwu Xu Quanxi Jia Wenge Yang Mercouri G Kanatzidis Ho-Kwang Mao 《国家科学评论(英文版)》2021,8(9)
Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties. Addressing their relationships is considerably challenging due to the scarcity of effective diagnostic tools during structural and property tuning as well as the limited tunability achievable by conventional methods. Here, using pressure and chemical methods to regulate the metal off-centering distortion, we demonstrate the giant tunability of photoluminescence (PL) in both the intensity (>20 times) and wavelength (>180 nm/GPa) in the highly distorted halide perovskites [CH3NH3GeI3, HC(NH2)2GeI3, and CsGeI3]. Using advanced in situ high-pressure probes and first-principles calculations, we quantitatively reveal a universal relationship whereby regulating the level of off-centering distortion towards 0.2 leads to the best PL performance in the halide perovskites. By applying this principle, intense PL can still be induced by substituting CH3NH3+ with Cs+ to control the distortion in (CH3NH3)1-xCsxGeI3, where the chemical substitution plays a similar role as external pressure. The compression of a fully substituted sample of CsGeI3 further tunes the distortion to the optimal value at 0.7 GPa, which maximizes the emission with a 10-fold enhancement. This work not only demonstrates a quantitative relationship between structural distortion and PL property of the halide perovskites but also illustrates the use of knowledge gained from high-pressure research to achieve the desired properties by ambient methods. 相似文献
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This study investigates whether university students’ epistemic beliefs and prior knowledge about controversial socioscientific issues (SSIs) can predict the different types of arguments that students construct. Two hundred forty-three university students were asked to construct different types of supportive arguments—social, ethical, economic, scientific, ecological—as well as counterarguments and rebuttals after they had read a scenario on a SSI. Participants’ epistemic beliefs and prior knowledge were assessed separately. Results showed that students’ epistemic beliefs and prior knowledge predicted the quantity, quality, and diversity of the different types of arguments the students constructed. In particular, students who held sophisticated epistemic beliefs about the structure of knowledge and exhibited relatively more robust prior knowledge scores, produced arguments of greater quantity, better quality, and higher diversity than students with less sophisticated epistemic beliefs and low prior knowledge scores. Educational implications are discussed. 相似文献
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The present study examined possible interactive links between empathy (cognitive and affective), moral disengagement (MD) and various bullying forms using a mediation model in 301 Greek early adolescents (10–12 years old). Results indicated that both dimensions of empathy were significantly negatively correlated, whereas MD was positively correlated with bullying forms. Two mediation models were tested separately for each gender. Mediation analysis indicated that boys with low affective, but not cognitive, empathy were more likely to demonstrate morally disengaged behaviour which in turn increased self-reported bullying involvement. Moreover, boys with high MD were more likely to report cognitive and affective empathy which resulted in greater direct and indirect relational bullying. In the case of girls, low affective and cognitive empathy evoked highly morally disengaged behaviour which triggered greater involvement in several bullying forms. Finally, cognitive and affective empathy partially mediated the link between MD and all forms of bullying for girls. The findings are discussed in the light of the relevant literature and implications for practice. 相似文献
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Nickolas D. Charistos Vasilios I. Teberekidis Constantinos A. Tsipis Michael P. Sigalas 《Education and Information Technologies》2003,8(4):369-379
In this paper the design and development of 3DNormalModes, an educational tool for interactive visualization and three dimensional perception of vibrational spectra data of molecules is presented. The details of the architecture of the tool and its functionality are described. Means of application in chemical education at university level are discussed. A pilot study summarizes the strengths, the educational value and the possible extensions of the system. 相似文献
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The notion of historical “parallelism” revisited: historical evolution and students’ conception of the order relation on the number line 总被引：1，自引：1，他引：0
This paper associates the findings of a historical study with those of an empirical one with 16 years-old students (1st year
of the Greek Lyceum). It aims at examining critically the much-discussed and controversial relation between the historical
evolution of mathematical concepts and the process of their teaching and learning. The paper deals with the order relation
on the number line and the algebra of inequalities, trying to elucidate the development and functioning of this knowledge
both in the world of scholarly mathematical activity and the world of teaching and learning mathematics in secondary education.
This twofold analysis reveals that the old idea of a “parallelism” between history and pedagogy of mathematics has a subtle
nature with at least two different aspects (metaphorically named “positive” and “negative”), which are worth further exploration.
相似文献
| Constantinos Tzanakis (Corresponding author)Email: |
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Constantinos M. Kokkinos Georgia Panayiotou Aggeliki M. Davazoglou 《Psychology in the schools》2005,42(1):79-89
The purpose of this study was to assess whether burnout and personality were linked to the perceived severity of 24 undesirable student behaviors among experienced and trainee teachers. Results indicated that teaching experience, student gender, and type of behavior were important determinants of their perceptions. Burnout had a significant effect on the severity ratings of antisocial and oppositional/defiant behaviors, suggesting that the more stressed teachers are, the less tolerant they become of such challenging and aversive behaviors. With regard to personality, severity ratings of students' undesirable behaviors were associated with high levels of conscientiousness and neuroticism. Findings indicate that burnout and personality provide a lens through which teachers appraise the severity of students' behaviors. © 2005 Wiley Periodicals, Inc. Psychol Schs 42: 79–89, 2005. 相似文献