Synthesis of a selenium and germanium containing random copolymer as an acceptor for all‐polymer solar cells

Abstract

For the need of electron‐transporting and electron‐affinity materials, n‐type polymers (as acceptor) have gained a lot of attention recently. We have synthesized a selenium and germanium containing copolymer as the acceptor for all‐polymer solar cells (all‐PSCs). The copolymer has larger p‐orbital selenium and germanium atoms for more electron transition from pi to pi* to enlarge light harvest of polymer. To prepare the copolymer, a monomer containing d‐orbital atom, selenium, was first synthesized from low‐cost starting materials. A random copolymer was prepared from the monomer with a commercial germanium containing monomer via palladium catalyzed Stille coupling reaction. Taking the side‐chain effect into account, we incorporated dodecyloxy group to increase the solubility of the polymer and also increase the coplanarity by oxygen–sulfur (S–O) interaction. Despite the low short‐circuit current density (Jsc) value, the random copolymer with 3d‐orbital electrons has the potential to be the candidate for n‐type material. In comparison, we also fabricated P3HT/PffBT4T‐2OD all‐PSCs, acquiring PCE of about 0.5% without any additive. POLYM. ENG. SCI., 58:387–394, 2018. © 2017 Society of Plastics Engineers