RESUMO
Two gallium porphyrins, a tetraphenyl GaCl porphyrin, termed as (TPP)GaCl, and an octaethylporphyrin GaCl porphyrin, termed as (OEP)GaCl, were synthesized to use as an electron cascade in ternary organic bulk heterojunction films. A perfect matching of both gallium porphyrins' energy levels with that of poly(3-hexylthiophene-2,5-diyl) (P3HT) or poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) polymer donor and the 6,6-phenyl C71 butyric acid methyl ester (PCBM) fullerene acceptor, forming an efficient cascade system that could facilitate electron transfer between donor and acceptor, was demonstrated. Therefore, ternary organic solar cells (OSCs) using the two porphyrins in various concentrations were fabricated where a performance enhancement was obtained. In particular, (TPP)GaCl-based ternary OSCs of low concentration (1:0.05 vv%) exhibited a ~17% increase in the power conversion efficiency (PCE) compared with the binary device due to improved exciton dissociation, electron transport and reduced recombination. On the other hand, ternary OSCs with a high concentration of (TPP)GaCl (1:0.1 vv%) and (OEP)GaCl (1:0.05 and 1:0.1 vv%) showed the poorest efficiencies due to very rough nanomorphology and suppressed crystallinity of ternary films when the GaCl porphyrin was introduced to the blend, as revealed from X-ray diffraction (XRD) and atomic force microscopy (AFM). The best performing devices also exhibited improved photostability when exposed to sunlight illumination for a period of 8 h than the binary OSCs, attributed to the suppressed photodegradation of the ternary (TPP)GaCl 1:0.05-based photoactive film.
RESUMO
This paper takes a practice-based approach to the study of cultural identity, focusing on how raw material and technical choices involved in the production of quotidian tools served to both reproduce, and reflect a social group's very way of being. We then consider the (dis)continuity of obsidian blade-making traditions from Middle-Late Bronze Age Malia (north-central Crete), i.e., before and after a period of island-wide destructions, and appearance of foreign elements believed to reflect the arrival of a population from the Greek mainland (Mycenaeans). Methodologically this involves an integrated, 'thick description' obsidian characterisation study to detail long-term cultural traditions, including the use of Neutron Activation Analysis (NAA) to source the raw materials of 36 artifacts. The results show a significant degree of continuity in the community's lithic traditions, suggesting that many of the innovative features at Malia can be interpreted in terms of local factions appropriating new and foreign means of social distinction, rather than wholescale changes in community composition.
Assuntos
Evolução Cultural , Vidro , GréciaRESUMO
The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma-optical-emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics.
