Device Architectures for Enhanced Photon Recycling in ThinFilm Multijunction Solar Cells

DOI: 10.1002/aenm.201400919 primarily due to the ineffective use of the entire solar spectrum. [ 1 ] Multijuction (MJ) cells, by contrast, spectrally split sunlight into sub-cells with different bandgaps, thereby providing pathways to greatly improved effi ciencies. [ 6–13 ] Conventional MJ cells require lattice matched or metamorphic epitaxial growth of the individual sub-cells. In addition, the serially connected sub-cells are constrained by current matching since the photocurrent of a two-terminal MJ device is determined by the smallest current among the sub-cells. These considerations constrain options in material selection, thereby creating practical challenges to the growth of more than three junctions in high performance cells. Our recent work demonstrates the ability to use printing techniques to assemble microscale, multijunction, multi-terminal cells with refractive-index matched interfaces, to yield ultrahigh cell and module effi ciencies. [ 13 ]