Synthesis of Alternating Low-Bandgap Conjugated Polymers Based on Dithieno[2,3-d: 2 ', 3 '- d '] naphtho[1,2-b: 3,4-b '] dithiophene and Enhancement of Photovoltaic Properties with Solvent Additives

摘要

Two alternating low-bandgap conjugated polymers with 10,11-di(3,7-dimethyloctyloxy)di-thieno[2,3-d:2,3-d]naphtho[1,2-b:3,4-b]dithiophene (NDT) as electron-donor moieties and N,N-di(2-hexyldecyl)isoindigo (ID) or bis(thieno-2-yl)-N,N-bis(2-hexyldecyl)-1,4-dioxo-pyrrolo[3,4-c]pyrrole (DPP) as electron-acceptor moieties, respectively named as PNDT-ID and PNDT-DPP, are firstly synthesized and characterized. The polymers exhibit appropriate energy levels, good solution processabilities and broad light absorption properties; the power conversion efficiencies (PCEs) of 0.16%-0.19% for the photovoltaic solar cells (PVCs) from the blend films of the polymers and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) are very low. The performances of the PVCs from the polymers are remarkably increased when a very small amount of 1,8-diiodooctance (DIO) or diphenyl sulfide (DPS) is used as solvent additives, and the maximal PCEs of 3.79% and 5.01% are respectively achieved in the PVCs from the blend films of PNDT-ID/PC71BM (W:W, 1:1.5) and PNDT-DPP/PC71BM (W:W, 1:1.5), with DPS as solvent additives under 100 mW cm(-2) illumination (AM 1.5G).