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Motivated by its potential properties and applications, the energy band alignment of the amorphous-crystalline Ge2Sb2Te5 heterojunction in thermal equilibrium is explored. An analytic model based on the exact solution to Poisson’s equation is constructed to describe the electrostatics of the heterojunction between the amorphous phase and the face-centred cubic crystalline phase of Ge2Sb2Te5. The model captures the physics of accumulation in the crystalline layer, as well as that of depletion and inversion due to the deep defect distributions in the bulk of the amorphous layer. Without introducing fitting parameters, the model approximates the influence of the density of states parameters of each phase on the electric potential distribution across the heterojunction. It is then validated against the exact solution obtained numerically using Solar Cell Capacitance Simulations. Apart from the small inaccuracy in modelling the electric potential distribution in the depletion region, simulation results reveal that the approximations are successful in modelling the electrostatics of the heterojunction.

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We establish a framework to examine the feasibility of using local vegetation for bioenergy power systems in small-scale applications and remote settings. The framework has broad application, and we present a specific case here to demonstrate the process. Our case study is the Tiwi Islands in northern Australia, where a large Acacia mangium plantation is a potential source of biofuel feedstock. Two types of technology were considered: 1. Bio-oil from pyrolysis in diesel generators and 2. Direct combustion coupled with a steam turbine. The biomass was characterized and found to have adequate properties for an energy crop, with a lower heating value of about 18 MJ/kg and entire tree ash content of 2%. Measurements from trees that were damaged from wildfires had similar results, showing potential value recovery for a plantation after unplanned fire. In comparison to a petroleum diesel-based generator, the bio-oil system was 12% more expensive. The direct combustion system was found to be the most economical of those explored here, costing as low as 61% of the bio-oil system. Additional social and environmental benefits were identified, including local employment opportunities, improved energy security and reduced greenhouse gas emissions. Our findings of high techno-economic potential of bioenergy systems, especially through direct combustion, are widely applicable to on-demand renewable energy supply in remote communities.