Postdoctoral Associate, Massachusetts Institute of Technology
Support the development of off-grid energy access programs in the developing world
According to a recent UN study approximately 2.1 billion people worldwide have unreliable or zero access to electricity. In a number of communities, access to modern energy services like affordable, cleaner and dependable heating, cooking, and lighting appear decades away. Given this background, the Off-Grid Energy Group at MIT’s D-Lab focuses on providing organizations based in these communities with the resources they need to design and implement programs that increase energy access in the communities they serve. The goal through this session is (1) to demonstrate our modular location agnostic energy needs assessment and then (2) to empower attendees with the tools and skills required to accomplish real time analysis of qualitative and quantitative data thus aiding in appropriate energy project generation. Most approaches to evaluation in the energy sector in developing countries occur once a particular intervention is implemented. This is a very top-down approach and may result in technology dis-adoption due to lack of finance, lack of proper maintenance and complications associated with behavior change within a community. D-Lab’s off-grid energy group believes in a more bottom-up process where working with local community based organizations an energy needs assessment is first conducted to identify the target community’s energy needs, expenditures and affordability. The assessment focuses on gathering information in the following areas:
Implications of this work Through project examples we hope to demonstrate to an audience that conducting a needs assessment first before implementing an energy solution may result in greater project success. Ideally, other practitioners in this space might want to follow a similar methodology in their work.
Abstract: We measure drift velocity in monolayer graphene encapsulated by hexagonal boron nitride (hBN), probing its dependence on carrier density and temperature. Due to the high mobility (>5 × 104 cm2/V/s) of our samples, the drift velocity begins to saturate at low electric fields (∼0.1 V/μm) at room temperature. Comparing results to a canonical drift velocity model, we extract room-temperature electron saturation velocities ranging from 6 × 107 cm/s at a low carrier density of 8 × 1011 cm–2 to 2.7 × 107 cm/s at a higher density of 4.4 × 1012 cm–2. Such drift velocities are much higher than those in silicon (∼107 cm/s) and in graphene on SiO2, likely due to reduced carrier scattering with surface optical phonons whose energy in hBN (>100 meV) is higher than that in other substrates.
Pub.: 07 Sep '17, Pinned: 30 Sep '17
Abstract: Black phosphorus (BP), a burgeoning elemental 2D semiconductor, has aroused increasing scientific and technological interest, especially as a channel material in field-effect transistors (FETs). However, the intrinsic instability of BP causes practical concern and the transistor performance must also be improved. Here, the use of metal-ion modification to enhance both the stability and transistor performance of BP sheets is described. Ag+ spontaneously adsorbed on the BP surface via cation–π interactions passivates the lone-pair electrons of P thereby rendering BP more stable in air. Consequently, the Ag+-modified BP FET shows greatly enhanced hole mobility from 796 to 1666 cm2 V−1 s−1 and ON/OFF ratio from 5.9 × 104 to 2.6 × 106. The mechanisms pertaining to the enhanced stability and transistor performance are discussed and the strategy can be extended to other metal ions such as Fe3+, Mg2+, and Hg2+. Such stable and high-performance BP transistors are crucial to electronic and optoelectronic devices. The stability and semiconducting properties of BP sheets can be enhanced tremendously by this novel strategy.
Pub.: 28 Sep '17, Pinned: 30 Sep '17
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