precursors, [4] doping proves challenging for solution-synthesized MC nanostructures. [5] Recently, post-synthesis halide treatment of nanocrystals in solution has been developed which involves switching halogens for long chain surfactant molecules absorbed on the surface. [2,6] In fact, sorption of halogens can be realized as part of a one-pot synthesis using metal halide precursors. [7] Although this strategy was initially developed for passivation of MC quantum dots against oxidation, [2,6,7] annealing or hot pressing halogen-coated nanoparticles allows halides to diffuse into the MC lattice and substitute for chalcogenide anions. [8] However, controlling doping levels is not straightforward and such methods can introduce rather high halide concentrations in small nanocrystals leading to reduced electrical conductivity. [8b] Hence exerting control over dopant concentration without sacrificing electrical performance is imperative.Thermoelectrics realize direct interconversion between thermal and electric energy, thus providing an important route An aqueous solution method is developed for the facile synthesis of Cl-containing SnSe nanoparticles in 10 g quantities per batch. The particle size and Cl concentration of the nanoparticles can be efficiently tuned as a function of reaction duration. Hot pressing produces n-type Cl-doped SnSe nanostructured compacts with thermoelectric power factors optimized via control of Cl dopant concentration. This approach, combining an energy-efficient solution synthesis with hot pressing, provides a simple, rapid, and low-cost route to high performance n-type SnSe thermoelectric materials.Doping plays a vital role in modifying the electronic properties of semiconductors and is pivotal for (opto)electronics, [1] photovoltaics (PV), [2] and thermoelectrics. [3] Metal chalcogenides (MCs) form a diversity of functional materials well-suited to such applications. Halogen doping in MCs has proven effective to realize n-type conducting behavior and tune carrier concentrations. [2][3][4] Enhanced thermoelectric and PV performance can result. [2][3][4] While halogens can be readily doped into bulk MCs by high-temperature synthesis using metal halide

A surfactant‐free solution methodology, simply using water as a solvent, has been developed for the straightforward synthesis of single‐phase orthorhombic SnSe nanoplates in gram quantities. Individual nanoplates are composed of {100} surfaces with {011} edge facets. Hot‐pressed nanostructured compacts (E g≈0.85 eV) exhibit excellent electrical conductivity and thermoelectric power factors (S 2 σ) at 550 K. S 2 σ values are 8‐fold higher than equivalent materials prepared using citric acid as a structure‐directing agent, and electrical properties are comparable to the best‐performing, extrinsically doped p‐type polycrystalline tin selenides. The method offers an energy‐efficient, rapid route to p‐type SnSe nanostructures.

The energy consumption from the expanding use of information and communications technology (ICT) is unsustainable with present drivers, and it will impact heavily on the future climate change. However, ICT devices have the potential to contribute significantly to the reduction of CO 2 emission and enhance resource efficiency in other sectors, e.g., transportation (through intelligent transportation and advanced driver assistance systems and self-driving vehicles), heating (through smart building control), and manufacturing (through digital automation based on smart autonomous sensors). To address the energy sustainability of ICT and capture the full potential of ICT in resource efficiency, a multidisciplinary ICT-energy community needs to be brought together covering devices, microarchitectures, ultra large-scale integration (ULSI), high-performance computing (HPC), energy harvesting, energy storage, system design, embedded systems, efficient electronics, static analysis, and computation. In this chapter, we introduce challenges and opportunities in this emerging field and a common framework to strive towards energy-sustainable ICT.

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As urfactant-free solution methodology,s imply using water as as olvent, has been developed for the straightforwards ynthesis of single-phase orthorhombic SnSe nanoplates in gram quantities.Individual nanoplates are composed of {100} surfaces with {011} edge facets.H ot-pressed nanostructured compacts (E g % 0.85 eV) exhibit excellent electrical conductivity and thermoelectric power factors (S 2 s)a t5 50 K. S 2 s values are 8-fold higher than equivalent materials prepared using citric acid as as tructure-directing agent, and electrical properties are comparable to the best-performing,extrinsically doped p-type polycrystalline tin selenides.T he method offers an energy-efficient, rapid route to p-type SnSe nanostructures.Growing global energy demands,together with the negative impacts resulting from combustion of fossil fuels,h ave diverted attention to technologies for sustainable energy generation and conversion.[1] Thermoelectrics realize direct inter-conversion between thermal and electrical energy and provide opportunities to harvest useful electricity from waste heat (and conversely to perform refrigeration). Thet hermoelectric conversion efficiencyo famaterial is determined by its dimensionless figure of merit, ZT= S 2 sT/k,where S, s, T, and k represent the Seebeck coefficient, electrical conductivity,a bsolute temperature,a nd thermal conductivity,r espectively.[2] Extensive efforts have been devoted to the improvement of the thermoelectric performance of state-of-the-art materials, [3] and to the discovery of new thermoelectrics [4] with ZT values > 2. Single-crystalline SnSe combines ah ighZTwith arelatively low toxicity and high Earth-abundance of the component elements.[4] SnSe crystals possess very low thermal conductivity owing to lattice anharmocity,y ielding record high ZTvalues of 2.6 and 2.3 at 923 Kalong the b and c crystallographic directions,r espectively.[4] Polycrystalline SnSe materials have been fabricated to improve mechanical properties, [5] but ZT has been limited to 1, owing to both increased electrical resistivity and thermal conductivity. [5] Unfortunately,t he synthesis of SnSe is protracted and energy-intensive,i nvolving heating, melting, and annealing at high temperatures ( % 800-1223 K). [4][5] Before the potential of SnSe can be realized, afast, cost-effective,and large-scale synthesis route to the pure selenide that does not sacrifice performance is essential.Nanostructuring very effectively enhances ZT. Theh igh density of interfaces improves phonon scattering, decreasing the lattice thermal conductivity. [2,3] Bottom-up solution synthesis methods facilitate control of size,m orphology,c rystal structure,and defects.[6] However,the organic surfactants that can control morphology through surface modification are commonly electrically insulating, which can drastically reduce the electrical conductivity of the materials.[7] Ligand replacement methods switch smaller species for long chain surfactant molecules, [7] but sometimes involve using high toxicity chemicals, ...