Charge carrier localised in zero-dimensional (CH3NH3)3Bi2I9 clusters

A metal-organic hybrid perovskite (CH3NH3PbI3) with three-dimensional framework of metal-halide octahedra has been reported as a low-cost, solution-processable absorber for a thin-film solar cell with a power-conversion efficiency over 20%. Low-dimensional layered perovskites with metal halide slabs separated by the insulating organic layers are reported to show higher stability, but the efficiencies of the solar cells are limited by the confinement of excitons. In order to explore the confinement and transport of excitons in zero-dimensional metal–organic hybrid materials, a highly orientated film of (CH3NH3)3Bi2I9 with nanometre-sized core clusters of Bi2I93− surrounded by insulating CH3NH3+ was prepared via solution processing. The (CH3NH3)3Bi2I9 film shows highly anisotropic photoluminescence emission and excitation due to the large proportion of localised excitons coupled with delocalised excitons from intercluster energy transfer. The abrupt increase in photoluminescence quantum yield at excitation energy above twice band gap could indicate a quantum cutting due to the low dimensionality.Publisher PDFPeer reviewe

Knowledge dynamics in the tourism-social entrepreneurship nexus

Tourism is often employed as a vehicle for facilitating social-economic development, however its usefulness has been somewhat limited in relation to addressing social issues, and in particular, those issues relating to poverty. This is partly due to the lack of cross-sectoral interactions and knowledge exchange between private, public and third sectors that are needed to create effective and appropriate initiatives to leverage tourism for social benefits. Such traditional sectoral boundaries can be broken down through social entrepreneurship approaches which concomitantly, facilitate the creation and synergizing of social innovation that addresses persistent social issues. Yet to date, the utility of cross-sectoral knowledge dynamics still remains largely under-researched in both the social entrepreneurship and tourism literature. This chapter introduces readers to the concept of knowledge dynamics and discusses knowledge dynamics in the tourism and social entrepreneurship nexus via a case study of community-based tourism in Mai Hich, Vietnam. We argue that by gaining an enhanced understanding of cross-sectoral knowledge dynamics, we can strengthen the overall praxis of tourism and social entrepreneurship, and in particular, assist policymakers in fostering conditions that generate increased innovation.Griffith Business School, Department of Tourism, Sport and Hotel ManagementNo Full Tex

Progress on lead-free metal halide perovskites for photovoltaic applications: a review

ABSTRACT: Metal halide perovskites have revolutionized the field of solution-processable photovoltaics. Within just a few years, the power conversion efficiencies of perovskite-based solar cells have been improved significantly to over 20%, which makes them now already comparably efficient to silicon-based photovoltaics. This breakthrough in solution-based photovoltaics, however, has the drawback that these high efficiencies can only be obtained with lead-based perovskites and this will arguably be a substantial hurdle for various applications of perovskite-based photovoltaics and their acceptance in society, even though the amounts of lead in the solar cells are low. This fact opened up a new research field on lead-free metal halide perovskites, which is currently remarkably vivid. We took this as incentive to review this emerging research field and discuss possible alternative elements to replace lead in metal halide perovskites and the properties of the corresponding perovskite materials based on recent theoretical and experimental studies. Up to now, tin-based perovskites turned out to be most promising in terms of power conversion efficiency; however, also the toxicity of these tin-based perovskites is argued. In the focus of the research community are other elements as well including germanium, copper, antimony, or bismuth, and the corresponding perovskite compounds are already showing promising properties. GRAPHICAL ABSTRACT: [Image: see text

Optoelectronic and material properties of solution processed Earth abundant Cu2BaSn S,Se 4 films for solar cell applications

Copper barium thioselenostannate, Cu2BaSnS4 xSex CBTSSe , absorbers employ low toxicity and abundant metals while offering low cost manufacturing options, controllable stoichiometry and band gap tunability from 2 eV at x 0 to 1.55 eV at x 3 . CBTSSe can therefore be considered a prospective candidate for maintaining or improving upon the advantages of already commercialized Cu In,Ga S,Se 2 CIGSSe and CdTe absorbers. In this study, we focus on solution deposited stoichiometric CBTSSe films with band gap of 1.59 eV x amp; 8776; 3 and explore the fundamental film properties. Temperature and excitation dependent photoluminescence studies reveal a dominant defect emission at 1.5 eV and a second deep defect feature at 1.15 eV. From time resolved terahertz measurements, we find a charge carrier electron and hole sum mobility of 140 cm2 Vs i.e., comparable to values in CIGSSe or Cu2ZnSnS4 xSex CZTSSe as well as a two component minority carrier lifetime. A longer lived lifetime component 2 ns arises from bulk recombination. However, strong recombination at the bare surface leads to a 50 ps lifetime, inferior to state of the art CIGSSe or CZTSSe absorbers. This recombination issue may worsen for CBTSSe CdS interfaces, due to a cliff like band alignment with 0.6 eV band offset, as revealed by ultraviolet photoemission spectroscopy. A low number of charge carriers within the absorber further contributes to a high series resistance. Employing these films, we also report the highest performance achieved from solution processed trigonal CBTSSe thin film photovoltaic devices, with open circuit voltage, short circuit current density, fill factor and efficiency of 470 mV, 14.3 mA cm2, 43.6 and 2.9 , respectively. The physical measurements provided on the stoichiometric solution processed CBTSSe absorber further point to critical areas for future improvement of CBTSSe and related photovoltaic cells in the quest for higher efficiency devices based on earth abundant metal