Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

Eidgenössisches Departement für
Umwelt, Verkehr, Energie und Kommunikation UVEK
Bundesamt für Energie BFE
THIN FILM CIGS SOLAR CELLS WITH A
NOVEL LOW COST PROCESS
Annual Report 2008
Author and Co-Authors A. N. Tiwari, C.Hibberd, Y.E. Romanyuk
Institution / Company ETH Zürich
Address Thin Film Physics Group, Technoparkstr. 1, 8005 Zürich
Telephone, E-mail, Homepage +41 (0) 44 633 79 49, Ayodhya.Tiwari@empa.ch,
http://www.tfp.ethz.ch
Project- / Contract Number 100964 / 152223
Duration of the Project (from – to) 01.11.2006 - 31.10.2008
Date 12.12.2008
ABSTRACT
A chemical process for incorporating copper into indium gallium selenide layers has been developed
with the goal of creating a precursor structure for the formation of copper indium gallium diselenide
(CIGS) photovoltaic absorbers. Stylus profilometry, EDX, Raman spectroscopy, XRD and SIMS
measurements show that when indium gallium selenide layers are immersed in a hot copper chloride
solution in ethylene glycole, copper is incorporated as copper selenide with no increase in the thickness
of the layers. The ion-exchange process in organic medium is advantageous over the aqua solution
technique, which was investigated in 2007, because no corrosion of the metal back contact is
observed, and it is possible to achieve sufficient Cu incorporation in thicker (In,Ga)2Se3 layers of
1.5-2 microns.
Further measurements show that annealing this precursor structure in the presence of selenium results
in the formation of CIGS and that the supply of selenium during the annealing process has a
strong effect on the morphology and preferred orientation of these layers. When the supply of Se
during annealing begins only once the substrate temperature reaches �400°C, the resulting CIGS
layers are smoother and have more pronounced preferred orientation than when Se is supplied
throughout the entire annealing process.
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