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Solution-processed metal halide perovskites (MHPs) have demonstrated great advances on achieving high-performance photodetectors. However, the intrinsic material instability and the toxicity of lead still hinder the practical applications of MHPs-based photodetectors. In this work, the first highly sensitive and fast-response lead-free perovskite photodetectors based on Cs2AgBiBr6 double perovskite films are demonstrated. A convenient solution method is developed to deposit high-quality Cs2AgBiBr6 film with large grain sizes, low trap densities, and long charge carrier lifetimes. Incorporated within a photodiode device architecture comprised of optimized hole- and electron-transporting layers, lead-free perovskite photodetectors are achieved exhibiting a high detectivity of 3.29 x 10(12) Jones, a large linear dynamic range of 193 dB, and a fast response time of approximate to 17 ns. All the key figures of merit of the devices are comparable with the reported best-performing photodetectors based on lead halide perovskites. In addition, the resulting devices exhibit excellent thermal and environmental stability. The nonencapsulated devices show negligible degradation after thermal stressing at 150 degrees C and less than 5% degradation in the photoresponsivity after storage in ambient air for approximate to 2300 h. The results demonstrate the great potential of the lead-free Cs2AgBiBr6 double perovskite in applications for environmentally friendly and high-performance photodetectors. ; Funding Agencies|National Natural Science Foundation of China [51472164]; 1000 Talents Program for Young Scientists of China, Shenzhen Peacock Plan [KQTD2016053112042971]; Educational Commission of Guangdong Province [2015KGJHZ006, 2016KCXTD006]; Science and Technology Planning Project of Guangdong Province [2016B050501005]; China Postdoctoral Science Foundation [2017M622744, 2018T110886]; Swedish Research Council FORMAS [942-2015-1253]; European Commission Marie Sklodowska-Curie Actions [691210]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

The Deepwater Horizon incident demonstrated that most of the oil left is deep offshore or in other difficult to reach locations. Moreover, obtaining the oil remaining in currently producing reservoirs requires additional equipment and technology that comes at a higher price in both capital and energy. In this regard, the physical limitations on producing ever-increasing quantities of oil are highlighted as well as the possibility of the peak of production occurring this decade. The economics of oil supply and demand are also briefly discussed showing why the available supply is basically fixed in the short to medium term. Also, an alarm bell for economic recessions is shown to be when energy takes a disproportionate amount of total consumer expenditures. In this context, risk mitigation practices in government and business are called for. As for the former, early education of the citizenry of the risk of economic contraction is a prudent policy to minimize potential future social discord. As for the latter, all business operations should be examined with the aim of building in resilience and preparing for a scenario in which capital and energy are much more expensive than in the business-as-usual one.

Light-emitting diodes (LEDs) based on organic-inorganic hybrid perovskites, in particular, 3D and quasi-2D ones, are in the fast development and their external quantum efficiencies (EQEs) have exceeded 10%, making them competitive candidates toward large-area and low-cost light-emitting applications allowing printing techniques. Similar to other LED categories, light out-coupling efficiency is an important parameter determining the EQE of perovskite LEDs (PeLEDs), which, however, is scarcely studied, limiting further efficiency improvement and understanding of PeLEDs. In this work, for the first time, optical energy losses in PeLEDs are investigated through systematic optical simulations, which reveal that the 3D and quasi-2D PeLEDs can achieve theoretically maximum EQEs of approximate to 25% and approximate to 20%, respectively, in spite of their high refractive indices. These results are consistent with the reported experimental data. This work presents primary understanding of the optical energy losses in PeLEDs and will spur new developments in the aspects of device engineering and light extraction techniques to boost the EQEs of PeLEDs. ; Funding Agencies|ERC [717026]; Carl Tryggers Stiftelse; European Commission [691210]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; National Basic Research Program of China [2016YFE0112000]; European Union [2016YFE0112000]; State Key Laboratory of Luminescent Materials and Devices at South China University of Technology [2017-skllmd-05]; State Key Lab of Silicon Materials at Zhejiang University [SKL2017-03]; China Scholarship Council [201506920047]; [2016-02051]

Future scenarios with significant anthropogenic climate change also display large increases in world production of fossil fuels, the principal CO2 emission source. Meanwhile, fossil fuel depletion has also been identified as a future challenge. This chapter reviews the connection between these two issues and concludes that limits to availability of fossil fuels will set a limit for mankind's ability to affect the climate. However, this limit is unclear as various studies have reached quite different conclusions regarding future atmospheric CO2 concentrations caused by fossil fuel limitations. It is concluded that the current set of emission scenarios used by the IPCC and others is perforated by optimistic expectations on future fossil fuel production that are improbable or even unrealistic. The current situation, where climate models largely rely on emission scenarios detached from the reality of supply and its inherent problems is problematic. In fact, it may even mislead planners and politicians into making decisions that mitigate one problem but make the other one worse. It is important to understand that the fossil energy problem and the anthropogenic climate change problem are tightly connected and need to be treated as two interwoven challenges necessitating a holistic solution.