Junction formation in chalcopyrite solar cells by sputtered wide gap compound semiconductors

In an effort to eliminate the CdS buffer layer and its costly preparation process we are considering sputtered buffer layers. In particular, we report in this contribution on the reactive sputtering of wide gap Zn O,S compound semiconductors and their application in solar cells with different types of chalcopyrite absorbers. While we were able to freely adjust the composition through the oxygen partial pressure, the structural and optical properties are superior when the composition is close to the ternary endpoints. Open circuit voltage and short circuit current density as a function of Sulphur content in the buffer show opposite trends. Working cells were achieved with low band gap as well as wide band gap absorbers, however, their performance is so far inferior to that of the standard stacks

Sputtered Zn O,S for junction formation in chalcopyrite based thin film solar cells

In an effort to eliminate the standard CdS buffer layer from chalcopyrite based thin film solar cells we have investigated sputtered Zn O,S films. They were prepared by partially re active sputtering from a ZnS target in an argon oxygen mix ture. Single phase, polycrystalline films were achieved for substrate temperatures of at least 100 C. Test devices pre pared in a completely dry process showed superior blue re sponse and active area conversion efficiencies up to 13.7

Current voltage characteristics and transport mechanism of solar cells based on ZnO nanorods In2S3 CuSCN

Temperature dependent current voltage characteristics in the dark and under illumination have been analysed on up to 3.2 efficient solar cells with extremely thin absorber based on ZnO nanorods In2S3 CuSCN structures. The diode ideality factor and the open circuit voltage are strongly influenced on a thermal activation process. Significant enhancement of the devices efficiency by annealing at moderate temperatures has been demonstrated. After this annealing the activation energy of the saturation current increased from 1.00 to 1.46 eV in the dark . Transport mechanisms at the In2S3 CuSCN interface region are discusse

Effect of internal surface area on the performance of ZnO In2S3 CuSCN solar cells with extremely thin absorber

Solar cells with an extremely thin light absorber were realized by wet chemical prepa ration on arrays of ZnO nanorods. The absorber consisted of an In2S3 layer thick ness 20 nm and its interface region with a transparent CuSCN hole conductor. By changing the length of the nanorods 0 3.3 m and keeping the In2S3 layer thickness constant at 20nm, the short circuit current increased from about 2 to 10 mA cm2 . A marked increase of the external quantum efficiency at longer wavelengths is attrib uted to light scattering and a solar energy conversion efficiency of 2.5 has been demonstrate

Band alignment at sputtered ZnSxO1 x Cu In,Ga Se,S 2 heterojunctions

Valence band offsets amp; 916;EVBM at ZnSxO1 x Cu In,Ga Se,S 2 CIGSSe heterojunctions have been studied by photoemission spectroscopy XPS, UPS as a function of composition x in sputtered ZnSxO1 x films. In the composition range from ZnO to ZnS we found amp; 916;EVBM between 2.1 0.3 eV and 0.8 0.4 eV, respectively. Considering the optical band gaps, the conduction band offsets amp; 916;ECBM range from 0.1 0.3 eV to 1.4 0.4 eV. These results suggest that sputtered ZnSxO1 x is suitable as substitution for the CdS buffer and ZnO window layers in standard chalcopyrite based solar cells. Current voltage characteristics of the solar cells have been investigated as a function of the composition

Formation of the charge selective contact in solar cells with extremely thin absorber based on ZnO nanorod In2S3 CuSCN

Annealed and not annealed solar cells with extremely thin absorber based on ZnO nanorod In2S3 CuSCN structures have been compared. Significantly higher external quantum efficiencies have been recorded on annealed devices. The temperature dependent current voltage characteristics in the dark and under illumination were analysed in detail. The short circuit current density increased with the temperature and depended on the light intensity by a power law with a power coefficient of 0.85 that was independent of the annealing or measurement temperature. The temperature dependence of the ideality factor dominated the temperature dependencies of the diode saturation current density and of the open circuit voltage. The activation energies increased strongly after annealing. We propose that the limiting charge selective contact is driven away from the highly defective In2S3 CuSCN interface into the In2S3 layer due to stimulated by the annealing Cu diffusio