Effect of dislocations in metal-insulator-semiconductor solar cells

The I–V characteristics are measured for a series of metal-insulator-semiconductor cells of Al–SiO2–pSi structure with dislocation loops penetrating different depths into the semiconductor surface. All cell parameters except reverse saturation photocurrent are observed to be degraded with increasing dislocation length. The reverse saturation photocurrent is independent of the extent of damage in the samples. The experimental results are explained in terms of a mathematical model based on hopping conduction of captured carriers along dislocations. The current along a dislocation is shown to vary, to the first approximation, as exp(qV0/2kT), contrary to the general expectation that such a current is linear in the voltage V0. To our knowledge, this is the first time that conduction along dislocations has been observed at room temperature.