Effect of alkyl side chains of twisted conjugated polymer donors on photovoltaic performance. (18th March 2021) - Lv, Qianglong
Abstract: This is an exciting topic on maximizing the photovoltaic performance for a given conjugated skeleton by optimizing the side chains. In this work, we report two conjugated polymers (P3TCO-D and P3TCO-DMO ) with the same conjugated backbone, the only difference in alkyl chains of carbonyl units (n-decyl and 3, 7-dimethyloctyl). Both polymers have similar molecular weights, polydispersity indexes, and molecular energy levels. The P3TCO-D has a stronger aggregation behavior than P3TCO-DMO . Interestingly, both pure polymer films have similar surface morphology. After blending with an electron acceptor of IT-4F, P3TCO-D : IT-4F film shows remarkable increased surface roughness of 23.2 nm and phase-separation. In contrast, 3TCO-DMO : IT-4F film displays slightly increased surface roughness of 3.82 nm and good phase-separation. In polymer solar cells, the P3TCO-D -based device gives a decent power conversion efficiency (PCE) of 10.1%, while the P3TCO-DMO -based device produces a better PCE of 12.8%. This work demonstrates that the optimization of side chains in the twisted conjugated polymers is very important to improve their photovoltaic performances. Graphical abstract: Image 1 Highlights: Twisted conjugated polymers were used to investigate the photovoltaic properties in non-fullerene polymer solar cells. Two twisted conjugated polymer donors with various alkyl side chains, P3TCO-D and P3TCO-DMO, were designed and synthesized. P3TCO-D has a stronger aggregation behavior than P3TCO-DMO. P3TCO-D : IT-4F-based device showed a PCE of 10.1%, in contrast, P3TCO-DMO : IT-4F-based device gave a better PCE of 12.8%.