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A dominant factor of the cycloreversion reactivity of diarylethene derivatives as revealed by femtosecond time-resolved absorption spectroscopy
摘要： Dynamics of the cycloreversion reaction of a photochromic diarylethene derivative with a small ring-opening reaction yield (～1%) was investigated by using femtosecond transient absorption spectroscopy. The reaction rate constant and activation barrier on the reaction coordinate were quantitatively analyzed on the basis of the temperature and excitation wavelength dependencies of the reaction yield and excited state dynamics. From the comparison of the present results with those in a more reactive derivative, we concluded that a key factor regulating the overall reaction yield is the branching ratio at the conical intersection where the excited state population is split into the product and the initial reactant. The excitation wavelength dependence of the dynamics indicated that the geometrical relaxation and vibrational cooling proceed in a few picosecond time scale behind the cycloreversion process, and the vibrational excess energy assists the molecule to climb up the energy barrier.
关键词： vibrational cooling,diarylethene derivative,photochromic,femtosecond transient absorption spectroscopy,cycloreversion reaction
更新于2025-09-19 17:13:59
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Modulating the luminance of organic light-emitting diodes via optical stimulation of a photochromic molecular monolayer at transparent oxide electrode
摘要： Self-assembled monolayers (SAMs) deposited on bottom electrodes are commonly used to tune charge carrier injection or blocking in optoelectronic devices. Beside the enhancement of device performance, the fabrication of multifunctional devices in which the output can be modulated by multiple external stimuli remains a challenging target. In this work, we report the functionalization of an indium tin oxide (ITO) electrode with a SAM of a diarylethene derivative designed for optically control the electronic properties. Following the demonstration of dense SAM formation and its photochromic activity, as a proof-of-principle, an organic light-emitting diode (OLED) embedding the light-responsive SAM-covered electrode was fabricated and characterized. Optically addressing the two-terminal device by irradiation with ultraviolet light doubles the electroluminescence. The original value can be restored reversibly by irradiation with visible light. This expanded functionality is based on the photoinduced modulation of the electronic structure of the diarylethene isomers, which impact the charge carriers’ confinement within the emissive layer. This approach could be successfully exploited in the field of opto-communication technology, for example to fabricate opto-electronic logic circuits.
关键词： photochromic,optoelectronic devices,diarylethene,Self-assembled monolayers,organic light-emitting diodes
更新于2025-09-19 17:13:59
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Nucleation mechanism of metal-vapor atoms on photochromic diarylethene surface with a low glass transition temperature
摘要： Metal pattern formation on organic surfaces is essential in organic electronics. Selective metal-vapor deposition using photochromic diarylethene (DAE) is a promising method to prepare ?ne metal patterns by maskless evaporation. Metal-vapor atoms are adsorbed, di?used, and then desorbed from the colorless surface with a low glass transition temperature. We, however, found that metal deposition started at a speci?c time (deposition-threshold time, tth) even on the colorless surface by continuous evaporation. tth was investigated using a quartz crystal microbalance. We elucidated that metal-nucleation sites were generated by chemical reactions between metal atoms and surface DAE molecules. The number of nucleation sites increases during metal evaporation and when the sites are located in the di?usion range of surface metal atoms, metal-atom nucleation for ?lm-formation starts. This is the origin of tth. This result would provide important knowledge for the preparation of electrodes for organic devices based on selective metal-vapor deposition.
关键词： organic electronics,nucleation mechanism,photochromic diarylethene,quartz crystal microbalance,metal-vapor deposition
更新于2025-09-10 09:29:36
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Ambipolar carrier transport in an optically controllable diarylethene thin film transistor
摘要： Ambipolar carrier transport is demonstrated in an optically controllable organic field-effect transistor, where a benzothienothiophene-substituted diarylethene (BTT-DAE) thin film is employed directly as the transistor channel. A closed-ring isomer, which is produced by ultraviolet (UV) light irradiation, allows the carrier injection of both holes and electrons from source-drain electrodes into the BTT-DAE layer. Moreover, alternate UV or visible (VIS) light irradiation induces marked switching in the drain currents caused by reversible photoisomerization between closed-ring (semiconductor) and open-ring (insulator) isomers. The light-driven on/off ratio, which is defined by the ratio of the drain currents in the sample after UV or VIS light irradiation, reaches 240 for hole transport. The value is comparable to the gate-voltage-induced on/off ratio of 160. Our findings, therefore, have a potential to lead to the construction of new optoelectronic devices such as photoreconfigurable logic circuits and light emitting transistors.
关键词： Ambipolar operation,Optical switching,Organic field-effect transistor,Diarylethene,Photochromism
更新于2025-09-09 09:28:46