High-Performance Ternary Nonfullerene Polymer Solar Cells with Both Improved Photon Harvesting and Device Stability

Efficiency and stability of polymer solar cells (PSCs) are the two most significant decisive factors for the purpose of actual applications. Here, highly efficient and stable ternary PSCs were fabricated by incorporating two well-compatible polymer donors (poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b0]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] and poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]) with one narrow band gap nonfullerene acceptor (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene)). It is found that Forster resonance energy transfer acts as an efficient pathway to further strengthen photon harvesting in this ternary system, which results in a significant improvement in current density (JSC) without sacrificing the strong absorption of binary blends in the n...