Enhanced charge-carrier transfer by CdS and Ag2S quantum dots co-sensitization for TiO2 nanotube arrays

Liu, Zhongqing; Ji, Gangqiang; Guan, Dexin; Wang, Bin; Wu, Xueliang

doi:10.1016/j.jcis.2015.06.038

Cited by 35 publications

(9 citation statements)

References 43 publications

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“…The bleach recovery time includes all the processes through which the system returns to its original ground state. The faster recovery time constant is due to the trapping processes of the photoexcited charge carriers, while the slower time components correspond to the long-lived states which may be due to radiative charge recombination or relaxation through a series of nonradiative channels Figure S3B) also agree with our assumption, as it is quite likely to have an enhanced defect density in the deposited film system as compared to its solution form.…”

Section: Resultssupporting

confidence: 82%

“…The faster recovery time constant is due to the trapping processes of the photoexcited charge carriers, while the slower time components correspond to the long-lived states which may be due to radiative charge recombination or relaxation through a series of nonradiative channels. 40 Faster decay kinetics of the CdS bleach signals as compared to CdS in chloroform (Figure S3B) also agree with our assumption, as it is quite likely to have an enhanced defect density in the deposited film system as compared to its solution form. The 457 nm signal represents a characteristic dynamic profile of a biexciton, which undergoes fast auger decay to produce its excitonic form followed by an excitonic decay process.…”

Section: Ultrafast Transient Absorption Studiessupporting

confidence: 85%

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Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

et al. 2020

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Chalcogenide-based type II heterojunctions are considered to be a promising candidate for optoelectronic device fabrication such as in solar cells, photodetectors, and light-emitting diodes. Type II heterosystems effectively help in the delocalization of charge carriers owing to facile band arrangements, preventing the recombination of photogenerated carriers resulting in improved photovoltaic efficiency. Herein, we report the synthesis of CZTS nanoparticles and CdS quantum dots using a facile and low-cost hot-injection method followed by fabrication of CZTS, CdS, and CZTS/CdS heterojunction thin films with the help of a spin-coating technique at room temperature. We demonstrated through a combination of steady-state photoluminescence and femtosecond pump–probe spectroscopy experiments that a type-II, staggered band alignment of a CZTS/CdS junction is encouraging for charge carrier transport. We monitored the ultrafast charge carrier dynamics in the junction and confirmed the efficient separation of photoexcited charge carriers in the CZTS/CdS heterojunction. In the CZTS/CdS heterojunction, the photoexcited electrons are transferred from CZTS to CdS, which resulted in a drastic increment of the bleach signal intensity compared to that of bare CdS. Similarly, the photoexcited holes are transferred from CdS to CZTS, monitored by steady-state and time-resolved spectroscopy. A slower bleach recovery confirms the spatial charge separation at the interface of the CZTS/CdS heterojunction, placing electrons and holes at CdS and CZTS, respectively. The controlled introduction of charge carriers and charge separation dynamics in the heterointerface reported here provides a promising approach toward designing CZTS-based solar cells and will open up new avenues for developing more efficient Cu chalcogenide-based photovoltaic and photocatalytic devices.

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Section: Resultssupporting

confidence: 82%

Section: Ultrafast Transient Absorption Studiessupporting

confidence: 85%

Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

et al. 2020

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“…This emission band shifts to higher wavelengths in the samples prepared at higher temperature. The excitonic peaks associated with the quantum dots observed in the UV-vis spectra of the samples prepared at temperature below 150 °C are translated as luminescent emissions located around 480 nm in its PL spectra [14,46,47]. The PL spectra of all samples also show a broader yellow emission band at 530-590 nm ( Figure 5), which according to the literature [44,45] are originated from surface defects due to the presence of interstitial cadmium or cadmium vacancies.…”

Section: Uv-vis Spectroscopy (Uv-vis)supporting

confidence: 55%

CdS Photocatalysts Modified with Ag: Effect of the Solvothermal Temperature on the Structure and Photoactivity for Hydrogen Production

et al. 2019

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This work studies the effect of the temperature in the solvothermal synthesis of CdS modified with Ag (Ag-CdS) over both the structure of CdS and the chemical state of the Ag species. The increase in the solvothermal temperature produces the evolution of the CdS nanostructures from nanoparticles of low crystallinity in coexistence with small nanocrystals with strong confinement effect to the formation of highly crystalline nanorods. The Ag species also change with the solvothermal temperature from Ag2S species, formed at low temperature, to metallic species as the temperature increases. The photoactivity of the Ag-CdS samples is the result of the combination of three factors: crystallinity of the CdS structures, existence of small nanocrystals with strong confinement effect and the presence of segregated Ag2S species. The Ag-CdS sample prepared at 120 °C shows the better efficiency for hydrogen production because it achieves the better combination of the aforementioned factors

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“…According to the intersection of the linear potential curve, the flat band potentials of C-CdS, C-Cu-CdS-0.5%, C-Cu-CdS-0.8%, C-Cu-CdS-1.0%, and C-Cu-CdS-2.0% are −0.79, −0.78, −0.76, −0.68, and −0.74 eV, respectively. By using E g = E vb – E cb , − the VBs of the as-prepared C-CdS, C-Cu-CdS-0.5%, C-Cu-CdS-0.8%, C-Cu-CdS-1.0%, and C-Cu-CdS-2.0% are calculated at 1.33, 0.88, 0.87, 0.92, and 0.84 eV versus SCE at pH 7, respectively. The relative VBs and conduction bands (CBs) of all of the samples obtained on the basis of the Mott–Schottky plots are presented in Figure f.…”

Section: Resultsmentioning

confidence: 99%

One-Step Solvothermal Synthesis of Petalous Carbon-Coated Cu⁺-Doped CdS Nanocomposites with Enhanced Photocatalytic Hydrogen Production

Liu

Ren

et al. 2017

Langmuir

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Metal ion doping and nanocoating a CdS photocatalyst have been proven to be effective strategies to inhibit photocorrosion and improve photocatalytic performance. In this study, carbon-coated Cu-doped CdS nanocomposites (C-Cu-CdS) with a stable petalous structure and highly uniform size distribution were successfully synthesized via a facile one-step solvothermal method. Both Cu doping and carbon coating to the CdS photocatalyst are realized in this one-step strategy. Benefiting from the unique core-shell structure and metal ion doping, the as-prepared C-Cu-CdS catalyst exhibits significantly enhanced photostability and visible-light-driven photocatalytic efficiency. For an optimal Cu doping percentage of 1.0%, an average hydrogen production rate of 2796 μmol h g and an apparent quantum efficiency of 16.0% at a wavelength of 420 nm was observed, the latter of which is nearly 9.3 times higher than that of the carbon-coated CdS product without Cu doping. The origin of the improved photocatalytic activity is systematically investigated by examining the effects of Cu doping.

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Enhanced charge-carrier transfer by CdS and Ag2S quantum dots co-sensitization for TiO2 nanotube arrays

Cited by 35 publications

References 43 publications

Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

CdS Photocatalysts Modified with Ag: Effect of the Solvothermal Temperature on the Structure and Photoactivity for Hydrogen Production

One-Step Solvothermal Synthesis of Petalous Carbon-Coated Cu⁺-Doped CdS Nanocomposites with Enhanced Photocatalytic Hydrogen Production

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Enhanced charge-carrier transfer by CdS and Ag2S quantum dots co-sensitization for TiO2 nanotube arrays

Cited by 35 publications

References 43 publications

Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

Probing Ultrafast Charge Separation in CZTS/CdS Heterojunctions through Femtosecond Transient Absorption Spectroscopy

CdS Photocatalysts Modified with Ag: Effect of the Solvothermal Temperature on the Structure and Photoactivity for Hydrogen Production

One-Step Solvothermal Synthesis of Petalous Carbon-Coated Cu+-Doped CdS Nanocomposites with Enhanced Photocatalytic Hydrogen Production

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One-Step Solvothermal Synthesis of Petalous Carbon-Coated Cu⁺-Doped CdS Nanocomposites with Enhanced Photocatalytic Hydrogen Production