The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminumⅢ(Alq_3) are investigated at room t...The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminumⅢ(Alq_3) are investigated at room temperature using steady-state and time-resolved transient photocurrent measurements as a function of doping concentration of Alq_3.Due to lower LUMO and higher HOMO energy level of Alq_3 than those of PVK,Alq_3 molecules may act as carrier trap states in PVK films at low concentration.However,at...展开更多
To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated u...To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages,and a wide range of excitation intensities are analyzed.For this purpose,conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used.After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current,the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility.By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers,the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained.Subsequently,the charge-carrier concentration-dependent mobility values were obtained,and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.展开更多
Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; t...Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies (VBi) to septuple Bi3+-sulfur vacancy associates (VBiBiBiSSSS). Furthermore, the concentration of septuple BiB+-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I2(sol), easily desorbs I-(sol), and enhances the electrocatalytic activity of the nanostructures.展开更多
基金Trans-Century Training Program Foundation for the Talents of Natural Science by the State Education Commission,Key Project of Chinese Ministry of Education (No.105041)National Natural Science & Foundation Committee of China (NSFC) (Nos.90401006,10434030 and 90301004)+1 种基金State key project of basic research (No.2003CB314707)the Key Laboratory of Specially Functional Materials and Advanced Manufacturing Technology,South China University of Technology,Ministry of Education,China.One of the authors (Hui Jin) is also grateful to the Doctor Innovation Foundation of Beijing Jiaotong University for financial support.
文摘The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminumⅢ(Alq_3) are investigated at room temperature using steady-state and time-resolved transient photocurrent measurements as a function of doping concentration of Alq_3.Due to lower LUMO and higher HOMO energy level of Alq_3 than those of PVK,Alq_3 molecules may act as carrier trap states in PVK films at low concentration.However,at...
基金This study was supported by the projects of National Research Foundation of Korea(Project No.:NRF-2018R1D1A1B07048843,Ministry of Education and NRF-2018K2A9A2A06023902,Ministry of Science and ICT)in addition to the program for Changbaishan Scholars of Jilin Province,China.
文摘To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages,and a wide range of excitation intensities are analyzed.For this purpose,conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used.After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current,the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility.By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers,the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained.Subsequently,the charge-carrier concentration-dependent mobility values were obtained,and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.
文摘Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies (VBi) to septuple Bi3+-sulfur vacancy associates (VBiBiBiSSSS). Furthermore, the concentration of septuple BiB+-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I2(sol), easily desorbs I-(sol), and enhances the electrocatalytic activity of the nanostructures.