| Title | Structural Characterization of a Composition Tolerant Bulk Heterojunction Blend |
| Publication Type | Journal Article |
| Year of Publication | 2014 |
| Authors | Huang, Ye, Xiaofeng Liu, C. Wang, James T. Rogers, G.M. Su, M.L. Chabinyc, E.J. Kramer, and G.C. Bazan |
| Journal | ADVANCED ENERGY MATERIALS |
| Volume | 4 |
| Pagination | 1301886 |
| Date Published | JUL 15 |
| ISSN | 1614-6832 |
| Abstract | The ratio of the donor and acceptor components in bulk heterojunction (BHJ) organic solar cells is a key parameter for achieving optimal power conversion efficiency (PCE). However, it has been recently found that a few BHJ blends have compositional tolerance and achieve high performance in a wide range of donor to acceptor ratios. For instance, the X2:PC61BM system, where X2 is a molecular donor of intermediate dimensions, exhibits a PCE of 6.6%. Its PCE is relatively insensitive to the blend ratio over the range from 7:3 to 4:6. The effect of blend ratio of X2/PC61BM on morphology and device performance is therefore systematically investigated by using the structural characterization techniques of energy-filtered transmission energy microscopy (EF-TEM), resonant soft X-ray scattering (R-SoXS) and grazing incidence wide angle X-ray scattering (GIWAXS). Changes in blend ratio do not lead to obvious differences in morphology, as revealed by R-SoXS and EF-TEM. Rather, there is a smooth evolution of a connected structure with decreasing domain spacing from 8:2 to 6:4 blend ratios. Domain spacing remains constant from 6:4 to 4:6 blend ratios, which suggests the presence of continuous phases with proper domain size that may provide access for charge carriers to reach their corresponding electrodes. |
| DOI | 10.1002/aenm.201301886 |
