Towards highly efficient 4-terminal mechanical photovoltaic stacks

At present renewable energy sources consist mainly of hydro power and wind energy, with the latter becoming increasingly important. However, the number of solar cells being produced yearly (in terms of watts produced by these solar cells under a standardized spectrum) has been growing consistently over the last 10 years, with growth rates between 25 and 70%/year; for 2005 solar cell production reached 1.7GW. This terrestrial photovoltaic (PV) market is currently dominated by flat plate modules incorporating Si solar cells. However, to sustain the present growth rate of terrestrial PV, the use of expensive semiconductor material must be minimized, necessitating the development of new technologies.