Two-dimensional simulation of thin-film silicon solar cells with innovative device structures

We investigate the optical and electrical properties of thin-film silicon s olar cells by means of numerical simulations. The optical design under inve stigation is the encapsulated-V texture, which is capable of absorbing sunl ight corresponding to a maximum short-circuit current density of 35 mA cm(- 2). Because the layer thickness can be restricted to only 4 mu m, the encap sulated-V structure also provides a good collection efficiency for photogen erated charge carriers. The results for our simulations suggest that practi cal efficiencies above 12% can be expected for Si material with a minority carrier lifetime as low as 10 ns. Increased lifetimes of 100 ns allow for a bout 14% efficiency. The benefit of multiple junctions within the device st ructure strongly depends on surface recombination. The efficiency of a sing le-junction cell can by improved by more the 3% absolute with a multi-junct ion device if the surface combination velocity is as high as 10(5) cm s(-1) . For moderate surface recombination, the gain is only 1%. Copyright (C) 19 99 John Wiley & Sons, Ltd.