Ternary blend bulk heterojunction photovoltaic cells with an ambipolar small molecule as the cascade material

Here we demonstrate that the power conversion efficiency of a P3HT:PC61BM bulk heterojunction solar cell can be improved from 3.4% to 4.3% by adding 10% of a cyclopent[hi] aceanthrylene derivative (CPA), which is an ambipolar small-molecule semiconductor, to form a ternary blend BHJ solar cell. This enhanced power conversion efficiency arises from improvement of both short-circuit current and open-circuit voltage because the addition of CPA not only provides absorption complementary to that of P3HT, but also leads to longer charge carrier lifetime in the bulk heterojunction.