I−III−VI 2 -semiconductor-based nanocrystals of ZnSe−AgInSe 2 solid solution ((AgIn) x Zn 2(1-x) Se 2 , ZAISe) with average sizes of 3.5−6.2 nm were successfully synthesized through thermal reaction of corresponding metal acetates and selenourea in a hot oleylamine solution. The optical property of ZAISe solid solution nanocrystals was tunable in a broad wavelength region from visible to near-infrared light by changing the composition of solid solution, where the energy gap of ZAISe nanocrystals was enlarged from 1.44 to 3.00 eV with an increase in the fraction of ZnSe in ZAISe, that is, with a decrease in x from 1.0 to 0. Both levels of conduction band and valence band edges, determined by photoelectron spectroscopy in air, were monotonously shifted to higher levels with an increase in the fraction of ZnSe. Quantum-dot-sensitized solar cells were fabricated with porous TiO 2 film electrodes immobilized with ZAISe nanocrystals using 3-mercaptopropionic acid as a cross-linking agent. The light conversion efficiency of the thus-obtained cells was enhanced by covering ZAISe nanocrystals with a CdS thin layer by the SILAR method. The photocurrent action spectra agreed well with absorption spectra of ZAISe nanocrystals immobilized on TiO 2 electrodes. Maximum energy conversion efficiency of 1.9% was obtained for the cell fabricated with ZAISe nanocrystals with x = 0.5 as a sensitizer under irradiation with simulated solar light of AM 1.5G. ■ INTRODUCTIONPhotovoltaic devices are one of the potential applications for colloidal semiconductor nanocrystals (NCs) because of their controllable physicochemical properties depending on their size. 1−6 Extending the optical absorption range of semiconductor NCs [quantum dots (QDs)] has been an important research subject to effectively utilize solar light, which contains light from the UV−vis to near-IR wavelength region. The size control of NCs has been a useful method to modify optical properties for semiconductor nanocrystals, such as CdSe, CdTe, and PbS, with the energy gap (E g ) of nanocrystals being enlarged due to the quantum size effect by decreasing particle size to less than ca. 10 nm. 7−9 Preparation of solid solution NCs has been another way to tune optical properties regardless of their particle size. 10−14 For example, solid solution NCs of ZnSe−CdSe (Zn x Cd 1-x Se) have been reported to have a tunable absorption onset from ca. 620 nm to ca. 500 nm by changing the chemical composition of x from 0 to 0.67, even though the average diameter of the solid solution NCs was enlarged with a decrease in the x value. 10 Colloidally synthesized nanocrystals have been useful light absorbers for the fabrication of quantum-dot-sensitized solar cells (QDSSCs). One possible strategy to improve the conversion efficiency of the device is to facilitate the charge separation of electron−hole pairs photogenerated in semiconductor NCs by appropriately adjusting the energy difference of conduction band edges (ΔE CB ) between semiconductor NCs and porous metal oxides as collecting electr...
What transforms society? Using the quintuple helix model (QHM) of social innovation, this study examines how the Okayama Education for Sustainable Development (ESD) project has transformed the local community and its people, and how this has led to global recognition. Okayama is known as a world leader in ESD and their unique approach is called the Okayama Model of ESD. This study further looks at the institutional configuration on the elements contributed to knowledge co-creation and how the key actors interacted to contribute to societal transformation through knowledge, social innovation, and institutional setting. The goal of this study is to outline the Okayama Model of ESD using the QHM lens constituted of five helices; education, politics, society, economy, and the natural environment. This study applies a qualitative research method, in which key actors who contribute most to the development of the Okayama Model of ESD are identified by content analysis and semi-structured interviews that are conducted using the life history method. The result shows that the firm ground of the political subsystem facilitates the interaction among the stakeholders in the three subsystems–education, social, and natural environment, which ultimately contributes to the joining of the economic subsystem and the initiation of the knowledge circulation process. Transformation necessitates a city-wide approach involving a network of multiple actors to collaborate for knowledge co-creation and circulation, and the establishment of a new social values system. The study revealed several key points of local action that accelerated the transformation process by helping in value creation, knowledge convergence, and system interaction, which was instilled early through all forms of education—multiple actors' interaction that shapes through the ESD project that stimulates the triangulation of mind, hearts, and hands. This way, the city of Okayama functions as a living laboratory for the Okayama Model of ESD. This situation naturally promotes Mode 3 of the knowledge co-creation system, and the principles of civic collaboration and citizen engagement developed through the Okayama Model of ESD have been elaborated in the prefecture-wide vision statement.
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