Formation of pn Homojunction in Cu(InGa)Se₂ Thin Film Solar Cells by Zn Doping

Abstract

In this study, a pn homojunction was intentionally fabricated in the Cu(InGa)Se2 (CIGS) layer by Zn doping. For Zn doping of the CIGS layer, Zn was evaporated after CIGS formation, and a potential improvement in cell performance was confirmed by this technique. Furthermore, Zn diffusion into the CIGS film was investigated by secondary ion mass spectroscopy (SIMS). A conductivity-type conversion from p-type to n-type was studied by the measurement of the cross-sectional electron beam-induced current (junction EBIC: JEBIC) and the spectral response of solar cells. A conversion efficiency of 11.5% has been achieved using the Zn-doped CIGS layer without a buffer layer and by the formation of a pn homojunction in the CIGS absorber.

Formation of Zn-doped CuInSe2 films by thermal annealing using dimethylzinc

“…In addition, Zn-doped CIGS layers can be formed by simple dry processes such as chemical vapor deposition, thermal evaporation, and thermal diffusion. However, few experimental results have been reported for the fabrication of pn junction using Zn-doped CuInSe 2 (CIS) bulk crystals [4][5][6][7][8] or CIGS films [9,10].…”

A Study of Doping Profile for the Site Selectively Zn‐Doped p‐type Cu(In,Ga)Se2 Thin Film for Solar Cell

“…It has been demonstrated that the CIGS film Zn doped at 1st stages exhibited increase in carrier concentration ( p = 10 16 ≈ 10 17 cm −3 ) which is higher than that of the corresponding undoped CIGS film by one order of magnitude. This result is in contrast to the n‐type conductivity of the CIGS films when Zn is doped at 2nd and 3rd stages . The solar cell using such p‐CIGS:Zn film exhibited V oc = 0.66V, I sc = 32 mA/cm 2 , FF = 69%, and η = 14.5%, which are higher than the corresponding intentionally undoped CIGS solar cells.…”

Quaternary Sputtered Cu(In,Ga)Se2Absorbers for Photovoltaics: A Review

“…Other effects related to n-type doping transitions and intermediate-band creation due to Zn and Sn doping, respectively, occur at much higher concentrations [107]- [109] and are unlikely to be a contributing factor to reduced device performance. Little is known of the effect of other impurities.…”