Excitation energy-dependent photocurrent switching in a single-molecule photodiode
Excitation energy-dependent photocurrent switching in a single-molecule photodiode
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DOI：
10.1073/pnas.1907118116
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
B. Shan;A. Nayak;Olivia F. Williams;D. C. Yost;N. Polizzi;Yanming Liu;Ninghao Zhou;Y. Kanai;
中科院分区：
文献类型：
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作者：
B. Shan;A. Nayak;Olivia F. Williams;D. C. Yost;N. Polizzi;Yanming Liu;Ninghao Zhou;Y. Kanai;
在基于分子激发态特性的光电器件中，由于激发态之间的快速相互转换，在控制波长相关特性方面存在一个主要挑战。在基于染料敏化光电极的光电化学电池中，表面功能化在指导入射光子的吸收和转换中起着重要作用。我们在这里证明了在基于氧化物的光电极中，光产生的电荷流的方向可以通过改变表面结合的、高度共轭的超分子发色团的激发态跃迁来控制，这对分子器件中的光电极设计具有重要意义。这种方法与共轭发色团和氧化物电极之间建立了良好的相关性，可以作为进一步开发太阳能转换装置的有效平台。分子光电器件中电子流的方向是由分子激发态和底层导体或半导体之间的电荷转移决定的。对于这些设备来说，控制电子流动的方向和可逆性是一个主要的挑战。我们在这里描述一个单分子光电二极管。它是基于一种内共轭的双色双偶体，具有化学连接（卟啉）锌（II）和双（三吡啶）钌（II）基团。在纳米晶、简并掺杂的铟锡氧化物电极上，二极体表现出明显的频率依赖性和电荷转移特性。在集成光电二极管的红光（~ 1.9 eV）和蓝光（~ 2.7 eV）激发之间的光源变化导致光电流在阴极和阳极之间切换。理论计算、激光闪光光解和稳态分光光度测量的结果表明，激发频率相关光电流的来源在于发色团激发态的电子结构。
Significance In optoelectronic devices based on the properties of molecular excited states, a major challenge exists in controlling wavelength-dependent properties, because of the rapid interconversion between excited states. In photoelectrochemical cells, based on dye-sensitized photoelectrodes, surface functionalization plays a significant role in directing the absorption and conversion of incident photons. We demonstrate here that the direction of photo-generated charge flow in an oxide-based photoelectrode can be controlled by varying the excited-state transitions in a surface-bound, highly conjugated supramolecular chromophore with important implications for photoelectrode design in molecular devices. This approach, with a well-established correlation between conjugated chromophores and oxide electrodes, can serve as an effective platform for further development of solar-energy conversion devices. The direction of electron flow in molecular optoelectronic devices is dictated by charge transfer between a molecular excited state and an underlying conductor or semiconductor. For those devices, controlling the direction and reversibility of electron flow is a major challenge. We describe here a single-molecule photodiode. It is based on an internally conjugated, bichromophoric dyad with chemically linked (porphyrinato)zinc(II) and bis(terpyridyl)ruthenium(II) groups. On nanocrystalline, degenerately doped indium tin oxide electrodes, the dyad exhibits distinct frequency-dependent, charge-transfer characters. Variations in the light source between red-light (∼1.9 eV) and blue-light (∼2.7 eV) excitation for the integrated photodiode result in switching of photocurrents between cathodic and anodic. The origin of the excitation frequency-dependent photocurrents lies in the electronic structure of the chromophore excited states, as shown by the results of theoretical calculations, laser flash photolysis, and steady-state spectrophotometric measurements.