Nanophase separation in organic solar cells

Organic photovoltaics (OPVs) are cost-effective thin-film devices that can be printed onto flexible substrates and integrated into building materials (Brabec et al. 2001; Thompson and Fréchet 2008). They are regarded as one of the most promising renewable energy sources for the near future (Mayer et al. 2007; Nelson 2011). In the past two decades, tremendous efforts from both academia and industry have been devoted to this quickly evolving field, leading to breathtaking improvement of the device power conversion efficiencies (PCEs) (Bian et al. 2012; Brabec et al. 2010; Dennler et al. 2008; Inganäs et al. 2009; Liang and Yu 2010). Up to now, a record efficiency of 10.6% has been obtained from polymer-based bulk heterojunction (BHJ) tandem devices (You et al. 2013). These achievements arose from improvement of materials and device optimization. However, further developments will rely more and more on a sophisticated interdisciplinarity of material science, device physics, interface science, and optical science. Such a highly interdisciplinary research frontier calls for more insightful contributions, for instance, further development and application of cutting-edge nanostructure characterization techniques, to address fundamental challenges in OPV research (Chen et al. 2012c; DeLongchamp et al. 2012; Liu et al. 2013a). Those characterization techniques will largely complement input from manufacturing engineering (such as innovative production instruments, processes, and ink formulas) to realize a path toward possible commercialization of OPVs (Krebs et al. 2010a,b; Søndergaard et al. 2012).