Junction Polymer Solar Cells

1 Principles of Multi-Junction Polymer Solar Cells 

Polymer Photovoltaics Materials, Physics, and Device Engineering 

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O. Adebanjo, et al, Triple junction polymer solar cells. Energy Environmental Science, 2013. 6(11) p. 3150-3170. 

W. Li, et al.. Efficient tandem and triple-junction polymer solar cells. Journal of the American Chemical Society, 2013.135(15) p. 5529-5532. 

Chen C-C, Chang W-H, Yoshimura K, Ohya K, You J, Gao J, Hong Z, Yang Y (2014) An efficient triple-junction polymer solar cell having a power conversion efficiency exceeding 11 %. Adv Mater 26 5670-5677... 

Figure 11.7 Structures of fullerene acceptors used in multi-junction polymer solar cells. References to the publications using these acceptors can be found in Table 11.1.

Table 11.2 Solution processed multi-junction polymer solar cells.

These advanees in triple-junction polymer solar cells show the potential for this type of device. Considering that in these triple junctions the photon energy loss ( loss) in each suhcell is at least 0.7 eV, and sometimes even above 1.0 eV (Table 11.2), it can be expected that by developing new materials in which is more tailored to 0.6 eV it will be possible to increase the efficiency of triple-junction solar cells considerably. In our view efficiencies in the 15-20% range are within reach. 

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... 

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