Michelle McCann

A review of thin-film crystalline silicon for solar cell applications. Part 2: Foreign substrates

Approximately half the cost of a finished crystalline silicon solar module is due to the silicon itself. Combining this fact with a high-efficiency potential makes thin-film crystalline silicon solar cells a growing research area. This paper, written in two parts, aims to outline world-wide research on this topic. The subject has been divided into techniques which use native substrates and techniques which use foreign substrates. Light trapping, vapour- and liquid-phase deposition techniques, cell fabrication and some general considerations are also discussed with reference to thin-film cells.

EXERGY ANALYSIS OF AMMONIA-BASED SOLAR THERMOCHEMICAL POWER SYSTEMS

The reversible dissociation of ammonia is one of the candidate reactions for use in closed loop solar thermochemical energy storage systems. The major determinant of achievable performance for such a system is the degree of thermodynamic irreversibility associated with the heat recovery process. Exergy analysis of a semi realistic 30 MPa isobaric system has revealed that the major irreversibilities occur within the exothermic reactor and the counterflow heat exchanger between ingoing and outgoing reactants. In this study, optimum reactor control yielded exergetic efficiencies up to 71%, which should translate to overall solar to electric conversion efficiencies of around 20%.

Boron doping of silicon layers grown by liquid phase epitaxy

This paper presents the results of a study of the incorporation of boron into silicon layers grown from a tin melt by liquid phase epitaxy. Boron was added to the melt through the use of boron-doped silicon source wafers. There is a large discrepancy between the amount of boron incorporated into the epitaxial layer and that available in the source wafer. This mismatch is explained by the gradual removal of boron from our system, most likely as a result of boron precipitation in the tin melt. This situation allows for control of the boron profile by adjusting the cooling rate and adding a dwell time. In this way, we have grown an epitaxial layer with an abrupt and highly doped p-type region at the epitaxial layer/substrate interface. This is useful for thin film solar cell applications as it allows the growth of a back surface field and a lightly doped bulk in a single growth step.