Semiconductor–semiconductor Heterojunction Cells
Semiconductor–semiconductor heterojunction (HJ) solar cells, composed of semiconductor materials 1 and 2 as seen in Figures 5.1 and 5.2, are the focus of this chapter. One of these materials of an HJ obviously must be an absorber. The other may be an absorber, too, or it may be a window material; i.e., a wider-gap semiconductor that contributes little or nothing to light absorption but is used to create the heterojunction and to support carrier transport. Window materials collect holes or electrons, function as majority-carrier transport layers, and can separate the absorber material from deleterious recombination at contacts. The interface they form with the absorber ...