在五烯/C60双层中,通过三重激子产生激子裂变和电荷生成
Akshay Rao1, Mark W B Wilson, Justin M Hodgkiss
1Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
Journal of the American Chemical Society
|August 26, 2010
概括
有机光伏设备通过单片裂变实现高量子效率. 这一过程涉及旋转三重激子扩散产生电荷,促进有机太阳能电池中的光电流.
科学领域:
- 材料科学 材料科学 材料科学
- 物理化学 物理化学
- 有机电子 有机电子
背景情况:
- 有机光伏 (OPV) 设备为灵活和大面积应用提供了潜力.
- 目前的OPV效率有限,阻碍了广泛采用.
- 五烯/C60) 双层被研究是因为它们独特的电荷生成特性.
研究的目的:
- 为了研究五/C60) 双层中电荷生成动态.
- 阐明激子在实现高量子效率中的作用.
- 探索单片裂变在提高OPV性能方面的潜力.
主要方法:
- 使用过渡光学吸收光谱学.
- 分析的重点是光刺激和电荷生成时间线.
- 研究了兴奋子的扩散和形成机制.
主要成果:
- 在五/C60) 双层中观察到异常高的量子效率.
- 发现电荷生成主要发生在光激发后2-10纳秒.
- 从早期 (<200 fs) 存在的三重激子,对于通过向异质连接的扩散产生电荷至关重要.
- 一个自旋单子激子的单点裂变成两个自旋三重子激子被确定为这些三重子的来源.
结论:
- 这项研究阐明了五/C60) 系统中激子和电荷生成动态.
- 单片裂变是有机光伏中增强光电流的关键机制.
- 调整有机分子能量水平以利用单片裂变可以显著改善未来的OPV性能.
相关概念视频
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:18Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
03:35Hybridization of Atomic Orbitals II
sp3d and sp3d 2 Hybridization
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:18Aromatic Hydrocarbon Anions: Structural Overview
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous overlap of p...
Due to the absence of continuous overlap of p...