Physical and virtual carbon metabolism of global cities.

Urban activities have profound and lasting effects on the global carbon balance. Here we develop a consistent metabolic approach that combines two complementary carbon accounts, the physical carbon balance and the fossil fuel-derived gaseous carbon footprint, to track carbon coming into, being added to urban stocks, and eventually leaving the city. We find that over 88% of the physical carbon in 16 global cities is imported from outside their urban boundaries, and this outsourcing of carbon is notably amplified by virtual emissions from upstream activities that contribute 33-68% to their total carbon inflows.

City-level climate change mitigation in China.

As national efforts to reduce CO emissions intensify, policy-makers need increasingly specific, subnational information about the sources of CO and the potential reductions and economic implications of different possible policies. This is particularly true in China, a large and economically diverse country that has rapidly industrialized and urbanized and that has pledged under the Paris Agreement that its emissions will peak by 2030. We present new, city-level estimates of CO emissions for 182 Chinese cities, decomposed into 17 different fossil fuels, 46 socioeconomic sectors, and 7 industrial processes.

Hybrid solar cells with prescribed nanoscale morphologies based on hyperbranched semiconductor nanocrystals.

In recent years, the search to develop large-area solar cells at low cost has led to research on photovoltaic (PV) systems based on nanocomposites containing conjugated polymers. These composite films can be synthesized and processed at lower costs and with greater versatility than the solid state inorganic semiconductors that comprise today's solar cells. However, the best nanocomposite solar cells are based on a complex architecture, consisting of a fine blend of interpenetrating and percolating donor and acceptor materials.

Controlled assembly of hybrid bulk-heterojunction solar cells by sequential deposition.

This work presents a technique to create ordered and easily characterized hybrid nanocrystal-polymer composites by sequential deposition of tetrapod-shaped cadmium telluride (CdTe) nanocrystals and poly(3-hexlythiophene). With controlled fabrication and composite morphology, these devices offer several advantages over traditional co-deposited hybrid cells and provide a model system for detailed investigation into the operation of bulk-heterojunction cells.

Air-stable all-inorganic nanocrystal solar cells processed from solution.

We introduce an ultrathin donor-acceptor solar cell composed entirely of inorganic nanocrystals spin-cast from solution. These devices are stable in air, and post-fabrication processing allows for power conversion efficiencies approaching 3% in initial tests. This demonstration elucidates a class of photovoltaic devices with potential for stable, low-cost power generation.