Photovoltaic properties of homojunction CIGS solar cells using various divalent n-type dopants

摘要

In order to investigate important factors required of N-type dopants for CIGS, various divalent ions,namely Mg, Ca, Mn Fe, Co, Ni, Cu, Zn and Cd, were doped as N-type dopants in CIGS thin films with the liquidphasedoping method and homojunction cells were fabricated. A maximum conversion efficiency of 17.7% wasobtained for Cd-doped homojunction cell but no phot°Currents were observed for Co-, Ni- and Cu-doped cells.Comparison with conversion efficiency and formal valence (V; estimated by bond valence sum calculation, BVS)revealed that conversion efficiency depends on formal valence and shows a peak at V = +3. Ions applied in a highefficiencycell seem to act as an effective N-type dopant. The above results indicate that the important factorsrequired of N-type dopants are the electronic configuration of the outermost electron shell and the coordinationenvironment determining the formal valence.