Morphology controllable organic solar cells

Abstract

<p indent=0mm>In recent years, ternary organic solar cells constructed from multi-component materials have attracting more and more attention. Since ternary organic solar cells are mainly prepared by blending multi-components and preparing the active layer of the device by solution processing, how to control the interaction force, phase separation and the aggregation scale of each component, as well as the way in which molecules are arranged by the introduction of the third component material are the studying focus. These factors have a large impact on the parameters such as the open circuit voltage, short circuit current, fill factor and the final power conversion efficiency of the ternary organic solar cells. This paper mainly summarizes the ternary organic solar cells based on PC₇₁BM as acceptor material. Firstly, by introduction of the third component material, alloy model charge transport in the ternary organic solar cell was introduced. The arrangement of the molecules in the active layer was investigated by grazing incident wide-angle X-ray scattering and resonance soft X-ray scattering. With the increase of small molecule donor incorporation ratio, the π-π stacking distance between molecules decreases gradually, which indicates that the introduced organic small molecule donor material is inserted into the polymer layer. It is more conducive to the transfer of charges between molecules. Afterward, the Cascade model and parallel model in the ternary system organic solar cell are summarized. Under different donors blending ratios, the coexistence of alloy model and parallel model in the same ternary system was realized. The two working models are both beneficial to the improvement of the performance of the ternary system. Especially, the conversion between alloy model and cascade model under the same blend ratio of the same ternary system was also realized. By studying the difference between the alloy model and the cascade model under the same blend ratio, we conclude that the cascade model is indeed more conducive to the separation of excitons and charge collection. Its power conversion efficiency is also more prominent. Lastly, topics of the development directions and prospect efficiency improve methods of the ternary organic solar cells are outlined. In summary, this review provides an in-depth understanding of the effective regulation of the phase separation scale and molecular arrangement of different components in the active layer of ternary organic solar cells and its relationship with device performance. This provides a reference for us to further improve device performance.