Multi-junction polymer solar cells photoactive layers

Although multi-junction polymer solar cells are a valid strategy for reaching high PCEs, the increased number of layers that have to be processed on top of eaeh other increases the complexity of the fabrieation process. The first important factor is solvent orthogonality. Each of the layers has to be proeessed from a solution that will not damage or wash away any of the previously deposited layers. For processing on top of a bulk heterojunction polymenfullerene, only a few solvents can be used in praetiee water, aeetone, and aleohols. Typically, the photoactive layers are hydrophobie and this represents an obstacle to the deposition of materials from aqueous solutions beeause of poor wettability. Therefore, extra measures have to be taken such... 

Several excellent reviews exist on polymer tandem solar cells and we refer to these publications for a comprehensive overview. In this chapter we focus on the materials requirements for creating efficient polymer solar cells and intermediate contact layers. In the following paragraphs, we will outline the operational principles in more detail. We will then review the most important photoactive materials used in polymer multi-junction cells and outline the material combinations that can used for the recombination layer. We conclude with an overview of recent achievements that have pushed the efficiency to well over 10% and address the progress in processing of large area tandem polymer solar cells. 

A further increase in the efficiency of polymer solar cells can be achieved by extending the multi-junction configuration from two to three or more photoactive layers. Multi-junction cells with more than two absorber layers are readily obtained using thermal evaporation of photoactive and... 

Polymer multi-junction cells have also achieved noticeable attention. In Table 11.2 we provide an overview of the multi-junction cells that had been published up to the end of 2014. In 2007, Gilot et al showed that it is possible fully to solution process three photoactive layers and two recombination layers based on ZnO/PEDO PSS and obtain a working triple junction solar cell with koc = 2. 19 By the same procedure, six-fold junction cells with... 

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