Bulk-Heterojunction with Long-Range Ordering: C60 Single-Crystal with Incorporated Conjugated Polymer Networks

Bulk-heterojunction (BHJ) blends are commonly used as active materials for optoelectronics. Ordering of molecular packing in blends is critical to their electronic properties, spurring investigation on how to obtain BHJ with long-range ordering. However, the difficulty in controlling crystallization during blending limits the crystallinity. Developing a new strategy instead of conventional blending is, thus, needed. Inspired by biomineralization, here, C-60 single-crystals are prepared in organogel matrix of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenvinylene] (MEH-PPV) to form MEH-PPV:C-60 composites. Essentially, networks of MEH-PPV are incorporated into growing C-60 crystals and penetrate throughout the crystals, resulting in crystal/gel-network interpenetrating composites. Despite the coexistence of MEH-PPV, the C-60 crystalline component maintains single-crystallinity and the composite exhibits as BHJ with long-range ordering. Furthermore, compared with blends, the long-range ordered BHJ shows a higher efficiency of charge dissociation and better performance in photodetection, exemplifying the advantage of ordering on organic electronics. Hence, this work provides a new platform to study BHJ with long-range ordering.