Bis-Azide Low-Band Gap Cross-Linkable Molecule N(3)-[CPDT(FBTTh(2))(2)] to Fully Thermally Stabilize Organic Solar Cells Based on P3HT:PC(61)BM.

We synthesized a novel bis-azide low-band gap cross-linkable molecule N(3)-[CPDT(FBTTh(2))(2)] with wide absorption. This compound is of interest as an additive in polymer/fullerene bulk heterojunction solar cells. In addition to providing efficient thermal stabilization of the morphology, the additive can harvest additional solar light compared with pristine poly(3-hexyl thiophene) to improve the power-conversion efficiency (PCE). The additional donor material was visualized from the appearance of additional external quantum efficiency contributions between 650 and 800 nm. An open-circuit voltage increase of ∼2% compensates the decrease in the short-circuit current of ∼2% to achieve a fully thermally stabilized PCE of 3.5% after 24 h of annealing at 150 °C.