Design Requirements for Highly Efficient Polymer Donors

1 Design Requirements for Highly Efficient Polymer Donors 

The value of Vqc for a PSC can be expressed by the empirical equation Foe = [ homo(D) - Elumo(A) 0.3 eV]/e, where e is the elementary charge, homo(D) is the highest occupied molecular orbital (HOMO) of the polymer and 0.3 eV 

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 typical electron mobility of PCBM is -10 cm V s , the should be at least 10 high performance donor polymers. 

Clearly, to obtain an ideal donor polymer, broader and stronger absorption, high hole mobility, and favorable morphology as well as suitable energy levels should be realized. 

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