Spiro-Shaped cis-Stilbene/Fluorene Hybrid Template for the Fabrication of Small-Molecule Bulk Heterojunction Solar Cells

A spiro core appended with trithiophene arms and α-cyanoacrylate end groups was used for the first time in bulk heterojunction solar cell applications. The resulting device performance was evaluated by its blending with PC61BM, leading to a short-circuit current density (Jsc) of 3.55 mA cm–2 which was 2.4 and 6.6 times better than those of the open form and nonspiro core analogs. The 1,8-diiodooctane solvent additive suppressed its microcrystalline self-aggregation, leading to a well-defined blend film morphology with reduced domain size and thus enhanced Jsc to 6.14 mA cm–2 and fill factor to 67.2% by 70% and 135% increase, respectively. The film domain size can be further reduced to 50 nm by its blending with PC71BM, leading to a PCE of 4.87% with an improved Jsc of 7.93 mA cm–2, a Voc of 0.97 V, and a fill factor of 64.1%.