Jack I. Hanoka

Influence of ion-implanted titanium on the performance of edge-defined, film-fed grown silicon solar cells

The electrical properties of edge‐defined, film‐fed grown and Czochralski silicon solar cells ion implanted with titanium have been investigated using deep level transient spectroscopy. In both types of solar cell materials, the observed degradation in cell performance is associated with the Ti deep level reported in earlier studies. During the cell fabrication sequence, Ti in‐diffuses into the bulk of the sample, creating a low‐lifetime zone extending beneath the junction. Solar cell modeling, based on the extent of the titanium‐diffused layer and the properties of the Ti center, is in excellent agreement with observed cell performance.

Measurement of diffusion length gradients in hydrogen passivated silicon ribbon

Hydrogen passivation of p‐type Si ribbon was studied by means of diffusion length measurements using the surface photovoltage (SPV) method. The effect of gradients in diffusion length on the SPV measurements and the median depth sampled by this method were investigated by numerical solution of the appropriate diffusion equations. The SPV technique was found to give an average of the diffusion length depth distribution with a median sampling depth of 70 μm. Up to threefold increases in diffusion length were observed due to passivation. Diffusion length profiling measurements made by etching away the surface showed significant passivation occurring at a depth of 200 μm.

Deep levels in edge‐defined, film‐fed grown silicon solar cells

Deep level transient spectroscopoy (DLTS) was used for studies of defects in edge‐defined film‐fed grown solar cells. For the first time, specific electronic traps were observed and identified in this polycrystalline silicon material. The DLTS spectra were taken in the extended temperature range 80–450 K, and a number of deep centers were detected. Several dislocation‐ and impurity‐related states were identified at low concentrations in the processed solar cells. Variations in crystal growth conditions were shown to produce a novel high‐temperature peak which exhibited a strong correlation to the bulk lifetime of the solar cell.