从分子内单片裂变产生的两个三重体状态之间的分离距离对两个电子转移过程的影响
Heyuan Liu, Xiangyang Wang, Lishuang Ma
1Shandong Energy Group Co., Ltd., Jinan, Shandong 250014, People's Republic of China.
Journal of the American Chemical Society
|August 5, 2022
概括
从单片裂变 (SF) 有效收获两个三重激子需要了解两电子转移. 库伦排斥,受三倍体间距离的影响,显著影响了这个过程.
科学领域:
- 光化学和材料科学
- 有机电子
- 能源转换
背景情况:
- 单片裂变 (SF) 是通过从单个光子产生多个激子来提高太阳能电池效率的一种有希望的机制.
- 通过两电子转移有效地收集两个三重激子对于最大限度地提高SF效益至关重要.
- 了解控制双电子转移过程的因素对于优化基于SF的技术至关重要.
研究的目的:
- 研究从分子内单片裂变 (iSF) 三重激子中影响两电子转移过程的关键因素.
- 用 TCNQ 接受器评估一系列四烯寡合体 (二聚体,三聚体,四聚体) 两电子转移的效率和动力学.
- 阐明库伦排斥和三重体间距离在两电子转移效率中的作用.
主要方法:
- 使用稳定状态和短暂吸收/光光谱来研究iSF和随后的两电子转移.
- 采用一系列四烯寡合物 (二聚,三聚,四聚) 和7,7,8,8-四氨基二甲基 (TCNQ) 作为电子受体.
- 执行理论计算以确定第二个电子转移的自由能量变化 (ΔG).
主要成果:
- 在三聚体和四聚体系统中实现了定量两电子转移,四聚体的速度更快.
- 在二极子系统中观察到相对较低的最大效率 (∼47%).
- 计算的 ΔG 值 (-0.024 eV 对于二聚体, -0.061 eV 对于三聚体, -0.074 eV 对于四聚体) 与实验效率相关,表明 ΔG 接近于零阻碍了转移.
- 在 ΔG 中的差异归因于可变的库伦排斥能,这取决于寡合体内的三重体间的距离.
结论:
- 证明库伦排斥能量受三重子间距离的影响,是控制iSF三重子激子两电子转移效率的关键因素.
- 分子的低效率与接近于零的 ΔG 值有关,这是由于三角间距离较短而导致的高库伦排斥.
- 这些发现为通过单片裂变有效收获多个激子的分子系统的设计提供了关键的见解.
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