Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr<sub>2</sub>O<sub>3</sub> Nanoparticle-Decorated InGaN/GaN Nanowires

Pu, Ying‐Chih; Kibria, Md Golam; Mi, Zetian; Zhang, Jin Z.

doi:10.1021/acs.jpclett.5b00909

Cited by 48 publications

(33 citation statements)

References 65 publications

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“…Before the detailed study of the exciton decay dynamics, we performed TA/TB measurements of the CdS and CdS/TiO 2 samples under three different pump powers of 230 nJ per pulse, 140 nJ per pulse, and 73 nJ per pulse to determine the possible power dependence of the dynamics since power dependent dynamics due to the nonlinear process can affect the interpretation of the results. [36][37][38][39] As shown in Fig. 7, the normalized maximum TB proles of each sample represented a relatively signicant difference as the pump power increased, however, the most similar recovery traces at a fast recovery component on a short time scale (0-20 ps) of all samples (insets of Fig.…”

Section: Charge Carrier Dynamics By Transient Absorption Spectroscopymentioning

confidence: 81%

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance

Han

Zheng

et al. 2015

J. Mater. Chem. A

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Core-shell CdS/TiO 2 structures are promising for solar-to-fuel conversion applications because their ideal type-II band alignment helps effective charge transfer to form the CdS + /TiO 2  system. A better understanding of the charge carrier dynamics is critical to provide guiding principles for designing photoelectrochemical (PEC) devices. Hence, TiO 2 shell-thickness dependent charge carrier dynamic and competition between electron relaxation in CdS (e.g. recombination and trapping) and electron transfer from CdS to TiO 2 were investigated using ultrafast transient absorption (TA) spectroscopy. The results indicate that the molar ratio of 2:1 CdS/TiO 2 nanocomposite exhibits the highest electron transfer rate constant of = 2.71×10 10 s -1 , along with an electron relaxation rate of / = 3.43 × 10 10 s -1 , resulting in an electron transfer quantum efficiency of Q ET = 79%, which also corresponds to the best PEC hydrogen generation in the CdS/TiO 2 core-shell composites.However, the electron transfer rate decreases with increasing thickness of the TiO 2 shell consisting of aggregated nanoparticles. One possible explanation is that the CdS and TiO 2 form relatively larger, separate particles, or less conforming small particles, with poor interface with increasing TiO 2 , thereby reducing electron transfer from CdS to TiO 2 , which is supported by SEM, TEM data and consistent with PEC results. Lived trap states contribute to the longer overall charge carrier lifetime or slower electron transfer centers. The thickness and morphology dependence of electron transfer and relaxation provides new insight into the charge carrier dynamics in such composite structures, which is important for optimizing the efficiency of PEC for solar fuel generation applications. 13 focused on the comparison of obtained TA data by the lowest pump power (73 nJ/pulse) to avoid the influence of high-order, nonlinear process. The TB feature of bandgap transition is proportional to the population of the hole population. 37 Therefore, the single-wavelength recovery of the TB features can be assigned to the exciton recombination of the CdS and CdS/TiO 2 core-shell composites, and their relation to the shell-thickness of TiO 2. The recoveries of the TB features of pure CdS and CdS/TiO 2 core-shell composites have been shown in Figure 8 (506 nm, 510 nm, 510 nm and 507 nm for pure CdS, 2:1 CdS/TiO 2 ,1:1 CdS/TiO 2 and 1:2 CdS/TiO 2 , respectively), and all the TB recoveries can be fit with a triple-exponential function. The lifetimes from the fitting are given inTable 1. For the pure CdS, the recovery of the fast component of 6±0.4 ps can be attributed to relaxation or cooling of the free electrons and holes due to excess kinetic energy following generation. The medium (34±2 ps) recovery component is attributed to nonradiative recombination through surface trap states. 43,44 The slow (450±22 ps) recovery component can be attributed to recombination of trapped electron-hole pairs. 45,46After TiO 2 shell is coated on CdS, the TB recovery of the 2:1 Cd...

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Section: Charge Carrier Dynamics By Transient Absorption Spectroscopymentioning

confidence: 81%

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance

Han

Zheng

et al. 2015

J. Mater. Chem. A

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“…Surface reaction sites are essential for carrier transportation and GaN materials’ photostability. Pu et al have shown that Rh/Cr 2 O 3 nanoparticles equipped InGaN/GaN nanowires with additional charge decay pathways can increase overall water splitting efficiency [ 13 ]. However, this efficiency is not comparable to that of materials such as SnO 2 and TiO 2 , because of the relatively low light absorption ratio of GaN materials [ 2 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

InGaN-based photoanode with ZnO nanowires for water splitting

Kang

Dang

et al. 2016

Nano Convergence

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The water splitting properties of InGaN photoanodes equipped with ZnO nanowires were examined in this study. Over the solar spectrum range, the absorbance exhibited a remarkable increase due to the enhanced light absorption caused by the ZnO nanowires. By varying the ZnO nanowires length, the photo-to-current density of photoanodes was increased from 0.017 to 0.205 mA/cm2 at 1.23 V versus reversible hydrogen electrode. Consequently, the incident-photon-to-current efficiency was increased by a factor of 5.5 as the ZnO nanowires growth time increased from 2 to 4 h. The results of this research demonstrate the importance of light absorbance and the surface reaction sites of photoanodes on energy harvesting.

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“…further investigated the charge carriers dynamics of InGaN/GaN NWs with loading Rh/Cr 2 O 3 core/shell nanoparticles. [ 141 ] The ultrafast femtosecond pump‐probe laser spectroscopy and a kinetic model demonstrate Rh/Cr 2 O 3 develops the medium time scale (≈50 ps) of exciton decay compared to excitation relaxation (≈33 ps) and excitation recombination (≈167 ps), which is attributed to the large k tran from the CB of InGaN/GaN NWs to Rh/Cr 2 O 3 nanoparticles and thus achieve the enhanced charge separation in InGaN/GaN NWs (Figure 8d). Chu et al.…”

Section: Recent Advances Of Surface/interface Structure Modulation Onmentioning

confidence: 99%

Section: Recent Advances Of Surface/interface Structure Modulation Onmentioning

confidence: 99%

Modulating Surface/Interface Structure of Emerging InGaN Nanowires for Efficient Photoelectrochemical Water Splitting

Lin

Wang

2020

Adv Funct Materials

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Photoelectrochemical (PEC) water splitting provides a promising approach to convert solar energy into hydrogen. Developing active, stable, and cost-effective semiconductors photoelectrodes is of great significance for achieving high-efficiency and large-scale hydrogen production. InGaN nanowires as an important candidate have gained a great upsurge in solar water splitting due to its tunable gap, high electron mobility, large active area, and excellent chemical stability. To obtain state-of-the-art InGaN nanowires-based photoelectrodes, tremendous efforts have been devoted to enhance light absorption capacity, charge carrier dynamics, and redox activity. In this review, recent advances in InGaN nanowires as photoelectrodes for PEC water splitting are comprehensively presented, with a focus on photoelectrode optimization strategies from the aspects of surface and interface structure modulation including doping engineering, energy band engineering, heterostructure engineering, and micro-nano engineering. The representative applications of InGaN nanowires-based PEC tandem cell are also discussed. Finally, perspectives on remaining challenges and future development are outlined.

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Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr₂O₃ Nanoparticle-Decorated InGaN/GaN Nanowires

Cited by 48 publications

References 65 publications

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance

InGaN-based photoanode with ZnO nanowires for water splitting

Modulating Surface/Interface Structure of Emerging InGaN Nanowires for Efficient Photoelectrochemical Water Splitting

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Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr2O3 Nanoparticle-Decorated InGaN/GaN Nanowires

Cited by 48 publications

References 65 publications

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO2 structures with optimized photoelectrochemical performance

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO2 structures with optimized photoelectrochemical performance

InGaN-based photoanode with ZnO nanowires for water splitting

Modulating Surface/Interface Structure of Emerging InGaN Nanowires for Efficient Photoelectrochemical Water Splitting

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Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr₂O₃ Nanoparticle-Decorated InGaN/GaN Nanowires

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance

Shell-thickness dependent electron transfer and relaxation in type-II core–shell CdS/TiO₂ structures with optimized photoelectrochemical performance