Design of Non-fused Ring Acceptors toward High-Performance, Stable, and Low-Cost Organic Photovoltaics
Design of Non-fused Ring Acceptors toward High-Performance, Stable, and Low-Cost Organic Photovoltaics
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面向高性能、稳定和低成本有机光伏的非熔环受体设计
DOI：
10.1021/accountsmr.2c00052
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发表时间：
2022-06-24
影响因子：
14.6
通讯作者：
Chen, Hongzheng
中科院分区：
文献类型：
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作者：
Shen, Qing;He, Chengliang;Chen, Hongzheng
展望：有机太阳能电池（OSCs）的未来商业应用，有机光伏材料能够实现高效率，优异的稳定性和低成本的开发。熔环电子受体（FREAs）已经宣布，OSCs能够显示超过19%的效率，而稳定性和成本尚未解决。作为FREAs的对应物，非熔合环电子受体（NFREAs）在分子设计上更具灵活性。由于断裂熔合主链降低了分子内张力，具有较好的稳定性；由于降低了合成的复杂性，在成本上具有较大的优势。然而，NFREAs面临的挑战是相对较低的效率（目前约为15%），这需要更好的分子设计来解决构象单一性和有效的分子包装问题。在本文中，我们从分子设计和效率优化、材料成本和稳定性三个主要框架全面总结了我们小组在NFREAs方面的工作。首先，在分子设计和效率优化部分，NFREAs中现有的可旋转单键会带来构象不确定的问题，但可以通过适当的分子设计来解决，并调节分子的能级、光吸收范围和包装方式，以获得更高的性能。因此，在这一部分中，我们将从分子骨架优化、末端修饰和侧链工程三个方面讨论NFREAs的演变。分子骨架的设计采用了多种策略，如利用类醌效应、引入具有电子推拉效应的官能团、使用多重构象锁等。此外，简化骨架也是首选的发展趋势。对于末端，主要的修饰策略是调整共轭长度和卤素原子。此外，通过调节侧链诱导适当的位阻，可以固定分子的取向，从而调节分子的排列方式。其次，关于材料成本，我们比较了最先进的FREAs和NFREAs的合成复杂性。由于NFREAs的合成过程减少了复杂的环化反应，因此大大简化了合成路线，只需三个最小步骤即可获得分子。第三，在稳定性方面，我们从材料固有稳定性、光稳定性和热稳定性的角度分析了nfrea的可行策略。最后，我们总结了nfrea应该克服的挑战，并提出了nfrea可以实现的前景，希望能够推动osc朝着高性能、稳定性和低成本的方向发展。
CONSPECTUS: Toward future commercial applications of organic solar cells (OSCs), organic photovoltaic materials that enable high efficiency, excellent stability, and low cost should be developed. Fused-ring electron acceptors (FREAs) have declared that OSCs are capable of showing efficiencies over 19%, whereas stability and cost are not solved yet. As the counterparts of FREAs, non-fused ring electron acceptors (NFREAs) are more flexible in molecular design. They have better stability because of the reduction of intramolecular tension via breaking fused backbone and have more advantages in cost with the reduction of synthetic complexity. However, the challenge for NFREAs is the relatively lower efficiencies (around 15% at current stage), which require better molecular designs for addressing the issues of conformational unicity and effective molecular packing.In this Account, we comprehensively summarize works about NFREAs carried out in our group from three main frameworks, including molecular design and efficiency optimization, material cost, and stability. First, in the part of molecular design and efficiency optimization, the existing rotatable single bond in NFREAs will bring the problem of conformational uncertainty, but it can be solved through proper molecular design, which also regulates the energy levels, light absorption range, and the packing mode of the molecule for obtaining higher performance. Thus, in this part, we discuss the evolution of NFREAs in three aspects, including molecular skeleton optimization, terminal modification, and side chain engineering. Many strategies are used in the design of a molecular skeleton, such as utilizing the quinoid effect, introducing functional groups with the electron push-pulling effect, and using multiple conformational lock. Furthermore, simplifying the skeleton is also the preferred development tendency. As for the terminal, the main modification strategy is adjusting the conjugation length and halogen atoms. What is more, by adjusting the side chain to induce appropriate steric hindrance, we can fix the orientation of molecules, thus regulating molecular packing modes. Second, regarding material cost, we compare the synthesis complexities between state-of-the-art FREAs and NFREAs. Because the synthesis processes of NFREAs reduce the complex cyclization reactions, the synthesis routes are greatly simplified, and the molecule can be obtained through three minimal steps. Third, regarding stability, we analyze the workable strategies used in NFREAs from the views of intrinsic material stability, photostability, and thermal stability. Finally, we conclude the challenges that should be conquered for NFREAs and propose perspectives that could be performed for NFREAs, with the hope of pushing the development of OSCs toward high performance, stability, and low cost.