16.6% efficient Silicon-Film/sup TM/ polycrystalline silicon solar cells

Comparing n- and p-type polycrystalline silicon absorbers in thin-film solar cells

“…An important motivation to the research effort on n-type multicrystalline silicon is that many, but by no means all, common transition metal impurities, such as molybdenum, vanadium, and especially iron, are more detrimental recombination centers for electrons than for holes [8][9][10][11][12]. Since the performance limiting impurities in multi silicon solar cells are oxygen, carbon, and transition metals [13], the use of n-type silicon could have an advantage over p-type silicon in the field of multicrystalline silicon solar cells. Finally, very high open circuit voltages have recently been achieved for solar cells based on n-type polycrystalline silicon thin films using liquid phase crystallization [14].…”

“…Apart from providing defect passivation, a hydrogen plasma treatment can also introduce harmful defects itself, such as surface damage, that requires an additional etch-back [13] to be removed in its turn. Hydrogenations may also induce hydrogen platelet defects, which have been reported to be more severe in n-type compared to p-type silicon [40].…”

The status of polysilicon feedstock

“…These Si layers, typically on the order of 100 um thick, are formed either free-standing or as coatings on alternative substrates such as high temperature glass, ceramics, or graphite (3)(4)(5)(6). Optical concentration can also be used to leverage the available Si supplies.…”