MINORITY-CARRIER DIFFUSION LENGTH IN SI-RIBBON SOLAR-CELLS

Minority carrier diffusion length L p in Si ribbon solar cells was investigated using a scanning electron microscope. It was found that L p was lowered at irregular crystal boundaries. The low L p region around an irregular boundary was only 10∼20 µm in width, and occupied less than 5 percent of the total solar cell area in most cases. The value of L p in regions without crystal boundaries scattered appreciably. Average L p value had no dependence on carrier density whose range was 1016∼1017 cm-3, which means that photocurrent is almost independent of carrier density. As a result, it is expected that ribbon crystals with higher carrier densities are preferable as base material for solar cells to obtain higher efficiency. © 1978 The Japan Society of Applied Physics.