Silicon solar cells by ion implantation - E-beam and self annealing

Experiments were performed to examine two techniques for annealing solar cells. P(+) ions were implanted, followed by e-beam annealing using a new electron gun with a beam width that can be varied, thereby eliminating the necessity for scanning. Other trials were run using a 50 W/sq cm ion beam for the implantation, thereby reaching a cell temperature of 1300 C, and the evidence for thermal self-annealing was scrutinized. Furthermore, a computer model was employed to study the effect of emitter tailoring on the cell efficiency. A total of 10 TiAg front grid, Al back contact, TiO2-SiO2 solar cells were tested and measured for the differential resistivity and the Hall effect. Self-annealed cells showed a better response to longer wavelengths, enough to offset the higher short-circuit currents available from electron beam annealing. Better I-V curve characteristics were observed after e-beam annealing, which indicated that 15 pct efficient AM1 cells are possible with this technique. The same efficiency is possible with self-annealing if homogeneous implantation can be achieved.