Three novel diketopyrrolopyrrole-based metal-free organic dyes (TPh, BPh and SPh) with different π-bridge lengths were designed and synthesized for dye-sensitized solar cells (DSSCs). The phenyl units were employed as the additional π-bridge for the three dyes, which located between the diketopyrrolopyrrole core and cyanoacrylic acid unit. Interestingly, it is the first time to report a diketopyrrolopyrrole-based dye with only one additional π-bridge unit (SPh). The effects of π-bridge length on photophysical, molecular planarity, energy level and photovoltaic properties of the dyes were systematically investigated. The results revealed that the prolongation of π-bridge length by introducing an additional phenyl unit results in an extra torsion in the structural framework and reduces the molecule planarity, which has a negative impact on improving the light-harvesting ability, while it is beneficial in lowering the tendency of aggregation and enhancing the excited electron injection efficiency. Finally, with a moderate π-bridge length (BPh), the best balance of overall performances is achieved, resulting in the highest power conversion efficiency (6.57%) without chenodeoxycholic acid.

为染料敏化太阳能电池 ( DSSC ) 设计并合成了三种具有不同 π 桥长度的新型二酮吡咯并吡咯基无金属有机染料（TPh、BPh和SPh）。苯基单元用作三种染料的附加 π 桥，位于二酮吡咯并吡咯核和氰基丙烯酸单元之间。有趣的是，这是第一次报道仅具有一个额外 π 桥单元 ( SPh)的基于二酮吡咯并吡咯的染料）。系统研究了π桥长度对染料光物理、分子平面度、能级和光伏性能的影响。结果表明，通过引入额外的苯基单元来延长 π 桥长度会导致结构框架中的额外扭转并降低分子平面度，这对提高光捕获能力具有负面影响，但有利于降低聚集趋势并提高激发电子注入效率。最后，通过适度的 π 桥长度 ( BPh )，实现了整体性能的最佳平衡，从而在没有鹅去氧胆酸的情况下实现了最高的功率转换效率 (6.57%)。