T Arc Photovoltaics Centre of Excellence 2010 / 11 Annual Report

There has been approximately equal work on the two major projects in Third Generation in 2010. These are the Group IV nanostructure tandem cells project the “all-Si” tandem cell and the Hot Carrier solar cell project, with its continuing funding from GCEP (Global Climate and Energy Project). There has also been further work on Up-conversion and on Plasmonics. The Si nanostructure work has seen increased understanding of the mechanisms for transport and quantum confinement. More sophisticated modelling of both has been tied more directly to improved interpretation of experimental results. This has led to establishment of a predictive ‘equivalent circuit modeller’ which will allow optimisation of Si QD device parameters to maximise transport and performance in the photovoltaic devices. Improved models for the understanding of doping effects in these materials have also been established. Work on alternate matrices for Si quantum dots, in both silicon nitride and carbide, has seen development of composite structures which have improved transport in the growth direction, whilst maintaining quantum confinement in the plane, but which also increase the uniformity of QD sizes. Work on Ge nanostructures has also improved with high electrical p-type conductivity established for Ge quantum dots and excellent pseudo single crystalline growth quality for Ge quantum wells in a nitride matrix. Heterojunction photovoltaic devices combining the advantages of two of these different material types are now being investigated. Hot Carrier cells have seen very significant improvement in demonstrated resonance in energy selective contacts using Si nanostructure layers, as well as a development of 2 and 3D modelling of transport in these structures. Modelling of Hot Carrier efficiencies continues to get more sophisticated with application to real material systems such as III-nitrides and inclusion of Auger processes which become significant at high carrier concentrations. Work on absorbers has allowed modelling of the phononic properties of a range of bulk materials, in conjunction with time resolved photoluminescence measurement of carrier cooling in some of these materials. Also modelling of coherent nanoparticle nanostructures, which emulate the phononic properties required, has developed into direct application to structures grown directly. These structures include the University Staff: • A/Prof. Gavin Conibeer (group leader) • Dr Richard Corkish • Prof. Martin Green Senior Research Fellows: