Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

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ZnO:Al/ZnO was deposited by rf-sputtering. Solar cells were completed by evaporation of Al/Ni contact
grids. No anti-reflection coating was applied to any of the cells in the present study. The currentvoltage
(J-V) characteristic of the solar cells, which have an area of 0.3 cm 2 , were measured under
simulated AM1.5 illumination (100 mW/cm 2 ) before (as-grown) and after air annealing of the
completed cells.
A detailed analysis of the In2S3 source material as a function of time of evaporation was carried out
using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy
(EDX). X-ray diffraction (XRD) patterns of the In2S3 powder and buffer layers deposited on SLG were
acquired using Cu-K� radiation.
Structural and chemical aspects of the source materials
The In2S3 source material for evaporation is heated to 720 - 740°C in a crucible to obtain desired flux.
Due to thermal decomposition of In2S3 a change in structure and chemical composition is expected
[10], which also depends on the heating duration. The microstructure of the source material as a
function of time of evaporation was studied. Fig. 1a and b show the SEM micrographs of powders-A
and -B, respectively after 4 min of evaporation.
a b
Figure 1: SEM image of In2S3 source material after 4 min of evaporation: (a) powder-A, (b) powder-B.
As a firsthand observation, the color of the powder-A changed to brown color while the powder-B
transformed into grayish bulk (Fig. 1b). It was noticed that the microstructure of the powder-A did not
show significant change even after 15 min of evaporation. In case of the powder-B, a considerable
microstructural contrast was observed at different positions of the bulk. Fig. 2 shows the SEM
micrographs of the powder-B acquired at different positions after 3 min (Fig. 2a and b) and 70 min
(Fig. 2c) of evaporation. The presence of well structured grains, as shown in Fig. 2a, was most
commonly occurring feature in the powder-B. The EDX analysis of those corresponding regions
revealed In1S1 composition. In addition, the occasional presence of bigger indium particles (Fig. 2b)
was also observed in EDX analysis.
a b
ATHLET, D. Brémaud, ETH Zurich Seite 97 von 288