Study On The Influence Of The Active Layer Morphology On The Performance Of PTB7:PC₇₁BM Polymer Solar Cells

Energy shortage and environmental pollution have become a big threat to human survival and development. Polymer bulk hetero-junction organic solar cells (OSCs for short) have the advantages of low cost and no pollution thus attracting more and more attention. In this paper, the choice PTB7:PC71BM as the active layer materials, a series of polymer solar cell device was prepared. By using solvent treatment and co-additives, I investigate the treatments in the active layer on the improved performance of polymer solar cells.First, I base on traditional PTB7:PC71BM polymer bulk hetero-junction solar cells, exploring the influence of the DIO and the methanol treatment on the polymer solar cell based in PTB7:PC71BM as an active layer, CB as the main solvent. A series of polymer solar cell devices with and without DIO additive as well as methanol treatment was fabricated. I explore the methanol treatment at different times, methanol treatment repeatly for the performance of the devices. Compared to the based device without additives, when 3 vol%DIO was used and methanol treatment 15 minutes after spin-coated films, the polymer solar cell has the highest photoelectric conversion efficiency. Methanol treatment does not increase the absorption of the active layer; the improved performance of polymer solar cells is mainly due to the optimization of the active layer’s morphology by the methanol treatment. Methanol treatment can make the film surface become smooth, and form a better interpenetrating networks structure in the bulk hetero-junction.Then, I base on traditional PTB7:PC71BM polymer bulk hetero-junction solar cells, exploring the influence of the co-additives DIO and PS on the polymer solar cell based in PTB7:PC71BM as an active layer, CB as the main solvent. A series of polymer solar cell devices without or with DIO and/or PS was fabricated. Compared to the based device without additives, when using co-additives, the polymer solar cell has the highest photoelectric conversion efficiency. Adding co-additives can increase the absorption of the active layer and improve the charge transport and collection, thereby increasing the short-circuit current and fill factor, the device performance has been greatly improved.