Blend charge carrier mobility

In conclusion, not only the observed larger scale of phase separation but also the difference in the material s phase percolation and thus charge transport properties influence the photovoltaic performance. As such, it becomes evident that the charge carrier mobility measured in these devices must be a function of the blend morphology [139-143]. Furthermore, the electron and hole carrier mobilities depend strongly on the polymer-fullerene blending ratio. Interestingly, the hole mobility of the donor polymer is increased considerably in blends with fullerenes (see Fig. 27) [142,144-147]. 

A. Babel and S. A. Jenekhe. Charge carrier mobility in blends of poly(9,9-dioctylfluorene) and poly(3-hexylthiophene). Macromolecules 36(20), 7759-7764 (2003). 

In fact, narrowing the band gap alone is not necessarily enough to achieve the expected /sc- Other parameters, such as charge carrier mobility, intermo-lecular interaction and molecular packing, have influence on /sc as well. Hole mobility (//h) is a significant parameter in evaluating the photovoltaic performance of novel donor polymers. In addition, balanced mobility should also be considered because FF is related to the ratio of hole-to-electron mobility of the D-A blends to some extent. Since the typieal electron mobility of PCBM is -10 cm V s , the should be at least 10 high performance donor polymers. 

Whereas in an LED, a high charge carrier mobility is not cmcial as what is required is balanced charge carrier mobilities, that is, the holes and electrons should have similar mobilities so as to promote recombination within the emissive layer, in a solar cell the charges need to be extracted expeditiously from the device. As a result, one method increasingly used to test the suitability of materials for BHJ solar cells is to measure their charge carrier mobilities, especially the mobilities when blended with the intended other component. Currently, a value of at least 10 cm Vs seems to be accepted as the... 

The blend enhanced charge carrier mobility, which improved the ternary blend photovoltaic performance in comparison to binary blends of D1 or D2 with PCgoBM. The AFM showed that the improvement is related to finer morphology in the ternary system of the active layer. 

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