Optimization of Active Layer Morphology for High-Efficiency Layer-by-Layer Organic Solar Cells with 18.13% Efficiency

The production of organic solar cells (OSCs) employing the layer-by-layer (LbL) casting approach is a very popular method nowadays. However, the diffusion of the acceptor during the LbL film formation process is uncontrollable and limited, which restricts the development of the LbL OSCs performance. To surmount this phenomenon, a novel LbL deposition strategy was adopted in this study. Traces of PY-IT were firstly added to the donor layer DIS-CI to utilize the poor miscibility between the two polymeric materials, which resulted in a blend film with a large phase separation. Subsequently, owing to the favorable miscibility of PY-IT with the acceptor layer material LS-BO, as well as the large phase separation of the DIS-CI:PY-IT film, the diffusion of LS-BO in the donor layer was effectively expanded. This induced a more desirable vertical morphology of active layer, thereby better balancing the charge generation, transport, and collection. For this reason, LbL OSCs based on DIS-CI:PY-IT/LS-BO achieved a power conversion efficiency (PCE) of IS.13%, which is a dramatic improvement versus the device based on DIS-CI/LS-BO (PCE of 17.16%). This study presents a novel and efficacious strategy for building efficient LbL OSCs.