IT Home News on January 2, organic solar cells (OSCs) have commercial potential in flexible portable devices due to their light weight, good flexibility and low cost. With the development of molecular design and the optimization of device processes, the efficiency of solar cells based on polymer donor/non-fullerene receptors has increased to more than 18%, but the problem of large differences in polymer batch size limits their commercial applications.
Compared with polymer solar cells (PSCs), solution-processable all-small molecule organic solar cells have a clear molecular structure, excellent material and device repeatability, and are conducive to industrial applications. The main difficulty of the small molecule system is the morphological regulation of the active layer, which limits the further improvement of efficiency.
According to the National Center for Nanoscience, The team of Wei Zhixiang, a researcher at the Key Laboratory of Nanosystems and Multi-level Subfabrication at the National Center for Nanoscience of the Chinese Academy of Sciences, is committed to the research of soluble organic small molecule solar cell materials, optimizing the morphology of the active layer, improving the performance of the device, achieving continuous improvement in battery efficiency, and developing a series of molecular design strategies to expand the understanding of the principle mechanism of small molecule solar cells.
Recently, the team cooperated with Qiu Xiaohui, a researcher at the National Nano center, to introduce the homologous polymer PJ1 of the receptor material as a phase interface compatibilizer based on the all-small molecule organic solar cell ZR-TT/Y6 to strengthen the interaction of the receptor, improve the morphology of the active layer to the receptor, and increase the energy conversion efficiency from 14.3% to 15.5%.
IT House learned that the results show that PJ1 is located in the donor interface in the active layer, which enhances the interaction between the donor receptors and makes the molecular accumulation in the active layer more dense, thereby optimizing the morphology of the active layer, accelerating the hole transfer rate, and finally obtaining an increase in energy conversion efficiency. The polymerization of small molecule receptor addition strategy is universal, which provides a new idea for the morphological optimization of all-small molecule organic solar cells.
In terms of new material design and synthesis, the team collaborated with Professor Harald Ade of North Carolina State University in the United States to design small molecule donors, and moved the thiol alkyl chain in the side benzene ring of small molecule donors from the paraposition to the interval, and designed and synthesized two small molecule donors P-PhS and M-PhS. Compared with P-PhS, M-PhS has improved molecular planarity and surface tension, and after blending with the small molecule receptor BTP-eC9, M-PhS maintains its ordered stacking ability while having good compatibility.
The results show that the device morphology based on M-PhS/BTP-eC9 has good crystallinity and multi-scale phase zone structure, realizes the co-optimization of exciton separation and charge transmission, improves the short-circuit current and fill factor at the same time, and achieves a record efficiency of 16.2% in binary all-small molecule solar cells. Studies have shown that while improving the crystallinity of materials, reducing the difference in surface energy of donor materials and acceptor materials to improve compatibility is an effective strategy for obtaining high-performance all-small molecule solar cells.
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