A 720 mV open circuit voltage SiO<i>x</i>:<i>c</i>-Si:SiO<i>x</i> double heterostructure solar cell

For maximal performance solar cells should resemble semiconductor lasers, i.e., they should be constructed in the form of a double heterostructure. We have found rather good performance in SIPOS-crystalline silicon-SIPOS double heterostructure solar cells, where SIPOS≡SiOx. The processing of these solar cells gives insights into the truly outstanding performance of the n+-SIPOS: p-Si heterojunction which has a forward saturation current coefficient J0=10−14 A/cm2, or equivalently an ‘‘emitter Gummel number’’ Ge=3.3×1015 s/cm4. This suggests that crystalline silicon solar cells can be much more efficient than had been suspected.