The development of high-efficiency plastic solar cells is rapidly accelerating as the need for economically viable alternative energy sources becomes evident. Polymer-based bulk-heterojunction (BHJ) solar cells are attractive in that they can be coated from solution onto flexible substrates by a variety of techniques and thus inexpensive large-volume manufacturing should be possible. Further, the inherent flexibility of the polymeric materials combined with thin photovoltaic active layers results in devices that can be adapted to a variety of unique aesthetics and form factors. Recent advances in key relationships between thin-film casting methods, bulk-heterojunction morphology, and device performance have occurred in tandem with the synthesis of novel polymer semiconductors that possess increased optical-absorption breadth and optoelectronic performance. This Research News article highlights a few techniques developed to optimize the BHJ nanomorphology and performance of solar cells fabricated by various solution-processing methods.