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Roll-to-roll processing of ITO-free organic solar cells

 
: Kaduwal, D.

:
Fulltext ()

Freiburg, 2015, IX, 131 Bl. : Ill.
Freiburg/Brsg., Univ., Diss., 2015
URN: urn:nbn:de:bsz:25-freidok-101560
English
Dissertation, Electronic Publication
Fraunhofer ISE ()

Abstract
Standard laboratory processed organic solar cells (OSCs) are fabricated in inert atmosphere with no significant time delays in between the fabrication steps. However for research case scenario only a single processing step is possible at a time with the R2R machine installed in ambient atmosphere as used in this dissertation work. A complete working day is needed for each of these processing steps taking into consideration the cleaning, preparatory work and deposition time. This results in delaying the following processing steps at least for one day exposing the layer stacks in ambient atmosphere. Therefore to understand the influence of processing and such time delays in ambient atmosphere on the final device performance all these processing parameters were replicated on small area devices. This led to the finding that all the layer stacks can be processed and stored in ambient atmosphere but with one limitation. The annealing of organic semiconductor, essential to get an optimum morphology and performance, was not possible in ambient atmosphere and must be done in nitrogen atmosphere. The R2R processed OSCs were limited in the performance (2.0%), mainly due to the solvent incompatibility of the solution processable metal inks deposited as a top contact. A printed top grid contact is attractive as vacuum processing of such a grid contact as used in the laboratory process would be too expensive. However for the OSCs where the top contact was thermally evaporated under vacuum, device performance of 3.5% of was achieved. The device efficiency of 3.5% is not only the highest values reported in literatures obtained for OSCs with R2R processed organic (P3HT:PCBM) layers but also the same that can be achieved with standard laboratory processing. This confirms that R2R processing of organic layers can be done in ambient atmosphere without loss in device performance and the issue with top grid contact needs to be solved. Experimentally obtained parameters were taken and module layout calculation showed that with the inverted setup as used in this dissertation work larger area modules with efficiencies of 3% can be fabricated. Cost calculations were done taking the actual material cost and resulted in the module cost of 1.4 €/WP mainly dominated by the organic material cost. However for large volume production where studies have shown that all material cost, in particular the organic material cost, are expected to be much less and thus the module cost of below 0.1 €/WP is achievable. Therefore R2R processing has the potential of low cost, lightweight and flexible OSCs with high throughput production.

: http://publica.fraunhofer.de/documents/N-408788.html