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

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The Athlet consortium comprises 23 partners from 11 EU countries, including 7 industrial partners,
research centers and academic institutions. Athlet is coordinated by HMI Berlin (D). Three Swiss partners
are participating: The University of Neuchâtel (IMT) which is coordinating SP IV (SP IV) while
also participating in SP I, Oerlikon Solar which is also participating in SP IV and the ETH Zurich (Prof.
A. Tiwari) is participating in SP I and III.
Results
Small area thin-film silicon cells
Cell development on small area cell was also performed in the framework of an OFEN project. The
progresses towards the objectives of 14% can be illustrated with the Fig. 2. The oblique lines correspond
to the Voc/Jsc values needed for achieving 14% with a given field factor value. The green area
represents the Voc/Jsc and FF values that we target. Recent progress and development of micromorph
cells is indicated by the red dots and arrows. We can observe that the introduction of a SiOx intermediate
reflector (SOIR) from the previous ZnO based intermediate reflector (ZIR) led to a significant
improvement of the Voc. Introduction of anti-reflecting coatings (ARC) on the glass led to an improvement
of the current. All values indicated in this figure are for the initial state.
June ’07
12.2%
270nm/1.8�m
Dec ’07
12.6% June ’08
SOIR
300nm/3�m (ARC)
12.8%
Nov ’05
11.6%
ZIR, 180nm/1.8�m
May ’06 375nm/3�m
300nm/3�m
11.8%
ZIR, 290nm/3�m
13.1%
Jsc,sum = 27.4 mA/cm2 June ’07
12.2%
270nm/1.8�m
Dec ’07
12.6% June ’08
SOIR
300nm/3�m (ARC)
12.8%
July ’08
13.3%
Nov ’05
11.6%
ZIR, 180nm/1.8�m
May ’06 375nm/3�m 340nm/3.5�m
300nm/3�m
11.8%
300nm/3.5�m
ZIR, 290nm/3�m(unmatched
tandem)
13.1%
Jsc,sum = 27.4 mA/cm2 July ’08
13.3%
340nm/3.5�m
300nm/3.5�m
(unmatched tandem)
Fig. 2: Recent progresses in the development of 1 cm 2 micromorph cells. Improvement were obtained
with the replacement of ZnO based IR (ZIR) by a SiOx based one (SOIR), introduction of antireflecting
coatings (ARC) and increase of the thickness. Thickness of a-Si:H cell and �c-Si:H
bottom cell are indicated. All efficiency values are in the initial state.
The improvement of the initial efficiency has been achieved mainly with an increase in the cell thickness,
an optimization of the SiOx intermediate reflector and the introduction of ARC layers on the glass
substrate. The best cell efficiency was 13.3% and the detailed characteristics are given in Fig. 3 [1].
The introduction of a SOIR and increase in cell thickness was expected to improve also the stable
efficiency. However, the thicker amorphous layer certainly impacts the stability (i.e. light induced degradation)
of the micromorph cell: the highest stable efficiency obtained so far is 11.2% (Voc=1.32V,
FF=66.8%, Jsc=12.7mA/cm 2 ).
ATLET, N. Wyrsch, Institut de Microtechnique
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