Semitransparent tandem solar cells

Transparent polymer solar cells (i.e., polymer solar cells with transparent electrodes) can be easily fabricated based on inverted architecture and have important application in tandem architectures as well. We can form transparent solar cells by replacing the Al top electrode with 12 nm Au in the inverted structure. The J-V curves for this transparent polymer solar cell, with light incident from ITO and Au side, are shown in Figure 11.17. The difference between the two J-V curves is due to the partial loss by the reflection and absorption at the semitransparent Au electrode. To provide sufficient electrical conductance, Au layer thickness has to be sufficient and the optical loss at Au electrode becomes significant. However, the inverted solar cell structure has the V2O5 layer which is not only transparent but also provides effective protection to the polymer layer. A transparent conductive oxides electrode, such as ITO, can therefore be deposited without compromising device performance. 

Over the last decade there has been enormous progress in tandem polymer solar cells. Advances have been made in terms of understanding, new photoactive materials, new interlayers, and device configurations (regular vs. inverted, parallel, semitransparent, etc). In Table 11.1 we provide a list of results obtained up to the end of 2014, following a more or less historical perspective and giving preference to listing the more salient results in terms of PCE. Table 11.1 lists the materials used in the front and back subcell. 

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