The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change ...The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films.展开更多
Femtosecond time-resolved transient grating technique was adopted to insight into the intra-chain exciton diffusion of MEH-PPV in solution with different polarity. Broadband white-light continuum was introduced as the...Femtosecond time-resolved transient grating technique was adopted to insight into the intra-chain exciton diffusion of MEH-PPV in solution with different polarity. Broadband white-light continuum was introduced as the probe to observe the transient absorption and the femtosecond time-resolved transient grating information simultaneously. The vibrational dephasing behaviors, single exciton relaxation, and population relaxation dynamics of MEH-PPV were systematically investigated. The result shows that the relaxation processes of the sample solution will be accelerated in the solvent with larger polarity.展开更多
The energy dissipation mechanism of energetic materials（EMs） is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption（TA） spectroscopy and time-resolved coheren...The energy dissipation mechanism of energetic materials（EMs） is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption（TA） spectroscopy and time-resolved coherent anti-stokes Raman scattering（CARS） to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes（VMs） in the ground state of nitrobenzene, which are located at 682 cm^-1（v1）, 854 cm^-1（v2）, 1006 cm^-1（v3）, and 1023 cm^-1（v4）,is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of vi and v2 modes, v1 and v4 modes, and v3 and v4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM.展开更多
The optical properties of three linear conjugated oligomers （F-P, F-P-F, and P-F-P-F-P）, where phenothiazine （P） and fluorene （F） groups arrange alternately, are investigated. With the enhancement of the π-conj...The optical properties of three linear conjugated oligomers （F-P, F-P-F, and P-F-P-F-P）, where phenothiazine （P） and fluorene （F） groups arrange alternately, are investigated. With the enhancement of the π-conjugated system, their absorption and emission bands both gradually red shift, and their two-photon properties are also improved. Meanwhile, their fluorescence dynamic traces are analyzed with continuous rate distribution model, exhibiting that their decay rates gradually accelerate and the rate distribution width become narrower. The quantum chemical calculation offers their molecular structures and transition mechanism, showing that the enhancement of π-conjugated system should be responsible for tile improvement of two-photon properties.展开更多
Achieving high efficiency and stable pure blue colloidal perovskite quantum dot(QD)light-emitting diodes(LEDs)is still an enormous challenge because blue emitters typically exhibit high defect density,low photolumines...Achieving high efficiency and stable pure blue colloidal perovskite quantum dot(QD)light-emitting diodes(LEDs)is still an enormous challenge because blue emitters typically exhibit high defect density,low photoluminescence quantum yield(PLQY)and easy phase dissociation.Herein,an organic cation composition modification strategy is used to synthesize high-performance pure blue perovskite quantum dots at room temperature.The synthesized FACsPb(Cl_(0.5)Br_(0.5))_(3) QDs show a bright photoluminescence with a high PLQY(65%),which is 6 times higher than the undoped samples.In addition,the photophysical properties of the FA cation doping was deeply illustrated through carrier dynamics and first principal calculation,which show lower defects,longer lifetime,and more reasonable band gap structure than undoped emitters.Consequently,pure blue FA-CsPb(Cl_(0.5)Br_(0.5))_(3) QDs light-emitting devices were fabricated and presented a maximum luminance of 1452 cdm^(−2),and an external quantum efficiency of 5.01% with an emission at 474 nm.The excellent photoelectric properties mainly originate from the enhanced blue QDs emitter and effective charge injection and exciton radiation.Our finding underscores this easy and feasible room temperature doping approach as an alternative strategy to blue perovskite QD LED development.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21573094,51502109,11774122,11574112,and 11474131)the National Found for Fostering Talents of Basic Science,China(Grant No.J1103202)the China Scholarship Council(CSC)obtained during the visit of Ning Sui to MPIA(Grant No.201706175038)
文摘The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films.
基金the National Natural Science Foundation of China，the Doctoral Scientific Research Staring Foundation of Zhijiang College of Zhejiang University of Technology
基金supported by the National Natural Science Foundation of China(No.61704120)Science & Technology Development Foundation of Tianjin Higher Education Institutions(No.20140904)
文摘Femtosecond time-resolved transient grating technique was adopted to insight into the intra-chain exciton diffusion of MEH-PPV in solution with different polarity. Broadband white-light continuum was introduced as the probe to observe the transient absorption and the femtosecond time-resolved transient grating information simultaneously. The vibrational dephasing behaviors, single exciton relaxation, and population relaxation dynamics of MEH-PPV were systematically investigated. The result shows that the relaxation processes of the sample solution will be accelerated in the solvent with larger polarity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21573094,11274142,11474131,11574112,and 51502109)the National Found for Fostering Talents of Basic Science,China(Grant No.J1103202)+1 种基金the Science Challenging Program(Grant No.JCKY2016212A501)China Scholarship Council(CSC) during a visit of Ning Sui(Grant No.201706175038) to MPIA is also acknowledged
文摘The energy dissipation mechanism of energetic materials（EMs） is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption（TA） spectroscopy and time-resolved coherent anti-stokes Raman scattering（CARS） to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes（VMs） in the ground state of nitrobenzene, which are located at 682 cm^-1（v1）, 854 cm^-1（v2）, 1006 cm^-1（v3）, and 1023 cm^-1（v4）,is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of vi and v2 modes, v1 and v4 modes, and v3 and v4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China. （No.21103161. No.11274142, No.11304058, No.11274034. and No.11004080） and the China Postdoctoral Science Foundation （No.2011MS00927 and No.2013T60319）.
文摘The optical properties of three linear conjugated oligomers （F-P, F-P-F, and P-F-P-F-P）, where phenothiazine （P） and fluorene （F） groups arrange alternately, are investigated. With the enhancement of the π-conjugated system, their absorption and emission bands both gradually red shift, and their two-photon properties are also improved. Meanwhile, their fluorescence dynamic traces are analyzed with continuous rate distribution model, exhibiting that their decay rates gradually accelerate and the rate distribution width become narrower. The quantum chemical calculation offers their molecular structures and transition mechanism, showing that the enhancement of π-conjugated system should be responsible for tile improvement of two-photon properties.
基金the National Natural Science Foundation of China(No.61804063)the National Key Research and Development Program of China(No.2019YFA0705900)funded by MOST.+4 种基金Key Projects of Jilin Province Science and Technology Development Plan(No.20220201070GX)the Natural Science Foundation of Jilin Province(No.20190201208JC)the support from the Hong Kong Research Grant Council for the GRF grant(No.11314122)research funding from the City University of Hong Kong and the support from Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302007)Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials(No.2019B121205002).
文摘Achieving high efficiency and stable pure blue colloidal perovskite quantum dot(QD)light-emitting diodes(LEDs)is still an enormous challenge because blue emitters typically exhibit high defect density,low photoluminescence quantum yield(PLQY)and easy phase dissociation.Herein,an organic cation composition modification strategy is used to synthesize high-performance pure blue perovskite quantum dots at room temperature.The synthesized FACsPb(Cl_(0.5)Br_(0.5))_(3) QDs show a bright photoluminescence with a high PLQY(65%),which is 6 times higher than the undoped samples.In addition,the photophysical properties of the FA cation doping was deeply illustrated through carrier dynamics and first principal calculation,which show lower defects,longer lifetime,and more reasonable band gap structure than undoped emitters.Consequently,pure blue FA-CsPb(Cl_(0.5)Br_(0.5))_(3) QDs light-emitting devices were fabricated and presented a maximum luminance of 1452 cdm^(−2),and an external quantum efficiency of 5.01% with an emission at 474 nm.The excellent photoelectric properties mainly originate from the enhanced blue QDs emitter and effective charge injection and exciton radiation.Our finding underscores this easy and feasible room temperature doping approach as an alternative strategy to blue perovskite QD LED development.
