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

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TANDEM CELLS
A possibility for enhanced efficiency is the introduction of an a-Si/a-Si tandem structure. Higher stabilized
efficiencies are expected because the tandem combines two individual cells with thinner absorber
layers and consequently better stability against light induced degradation. TABLE 1 compares
the differences in stabilisation between a single and a tandem cell with identical starting efficiency.
Table 1: Initial and stabilized efficiencies amorphous silicon tandem solar cells on glass.
Voc
[mV]
jsc
[mA/cm 2 ]
FF
[%]
single cell (initial) 883 14.7 70 9.1
single cell (stable) 885 13.6 60.6 7.3
tandem (initial) 1742 7.4 70.2 9.1
tandem (stable) 1705 7.3 63.9 8.0
Conclusions and Outlook
efficiency
[%]
During the reporting 2008 the work progressed closely to work plan in the proposal. Some difficulties
emerged during the development of the dielectric reflector and particularly during its integration into
the processing at Flexcell. In the proposal this part was anticipated as risky, but it also bears the highest
potential of improvements. In agreement with the risk strategy of the proposal, the partners agreed
to shift some of the time allotted to tandem development into this work package. The results presented
in TABLE 1 are already ahead of the anticipated milestones for the tandem work package which justifies
the decision.
The latest results of the project have been presented to the photovoltaics community at the occasion
of the European PV conference held in Valencia [1]. The presentation was well received and mentioned
as one the conference highlights during the closing session.
References
[1] O. Cubero, T. Söderström, F.-J. Haug, V. Terrazzoni-Daudrix, X. Niquille, S. Perregaux, M. Raeis-Barneoud and C. Ballif
Latest Results on stabilized flexible thin film silicon solar, Proc. 23 rd EU-PVSEC, 2008, Valencia.
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Flexible photovoltaics: next generation high efficiency and low cost thin film silicon modules, F.-J. Haug, Institute of Microtechnology IMT