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Significant improvements in InGaN/GaN nano-photoelectrodes for hydrogen generation by structure and polarization optimization.

ABSTRACT: The photoelectrodes based on III-nitride semiconductors with high energy conversion efficiency especially for those self-driven ones are greatly desirable for hydrogen generation. In this study, highly ordered InGaN/GaN multiple-quantum-well nanorod-based photoelectrodes have been fabricated by a soft UV-curing nano-imprint lithography and a top-down etching technique, which improve the incident photon conversion efficiency (IPCE) from 16% (planar structure) to 42% (@ wavelength?=?400?nm). More significantly, the turn-on voltage is reduced low to -0.6?V, which indicates the possibility of achieving self-driven. Furthermore, SiO2/Si3N4 dielectric distributed Bragg reflectors are employed to further improve the IPCE up to 60%. And the photocurrent (@ 1.1?V) is enhanced from 0.37?mA/cm(2) (original planar structure) to 1.5?mA/cm(2). These improvements may accelerate the possible applications for hydrogen generation with high energy-efficiency.

SUBMITTER: Tao T

PROVIDER: S-EPMC4745013 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Significant improvements in InGaN/GaN nano-photoelectrodes for hydrogen generation by structure and polarization optimization.

Tao Tao T Zhi Ting T Liu Bin B Li Mingxue M Zhuang Zhe Z Dai Jiangping J Li Yi Y Jiang Fulong F Luo Wenjun W Xie Zili Z Chen Dunjun D Chen Peng P Li Zhaosheng Z Zou Zhigang Z Zhang Rong R Zheng Youdou Y

Scientific reports 20160208

The photoelectrodes based on III-nitride semiconductors with high energy conversion efficiency especially for those self-driven ones are greatly desirable for hydrogen generation. In this study, highly ordered InGaN/GaN multiple-quantum-well nanorod-based photoelectrodes have been fabricated by a soft UV-curing nano-imprint lithography and a top-down etching technique, which improve the incident photon conversion efficiency (IPCE) from 16% (planar structure) to 42% (@ wavelength = 400 nm). More ...[more]

PMID: 26853933

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Project description:The intensive measures of luminescence in a GaN/InGaN multiple quantum well system are used to examine the thermodynamics and phenomenological structure. The radiative /nonradiative transitions along with absorbed or emitted phonons that occur between the different quantum states of the electrons and holes associated with these processes make the quantum efficiency of a semiconductor nanosystem in an equilibrium state an extensive property. It has long been recognized that tuning of the indium (In) composition in InGaN interlayers gives the potential to obtain a spectrum in the near-infrared to near-ultraviolet spectral range. The thermodynamic intensive properties, including the Debye temperature, carrier temperature, and junction temperature, are the most appropriate metrics to describe the optical-related interactions inherent in a given heterostructure and so can be used as the state variables for understanding the quantum exchange behaviors. The energetic features of the quantum processes are characterized based on analysis of the intensive parameters as determined by means of electroluminescence (EL) and photoluminescence (PL) spectroscopy and current-voltage measurement and then correlated with the designed InGaN/GaN microstructures. According to the McCumber-Sturge theory, the EL and PL Debye temperatures obtained experimentally signal the strength of the electron-phonon and photon-phonon interaction, respectively, while the EL and PL carrier/junction temperatures correspond to the carrier localization. Higher EL Debye temperatures and lower EL carrier/junction temperatures reflect significantly higher luminescence quantum yields, indicative of electron-phonon coupling in the transfer of thermal energy between the confined electrons and the enhancement by excited phonons of heat-assisted emissions. On the other hand, the observation of low luminescence efficiency, corresponding to the lower PL Debye temperatures and higher PL carrier/junction temperatures, is attributed to photon-phonon coupling. These findings are in good accordance to the dependence of the EL and PL quantum efficiency on the In-content of the InGaN/GaN barriers, suggesting that the characteristic Debye and carrier/junction temperatures are intensive parameters useful for assessing the optical properties of a nano-engineered semiconductor heterostructure.

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Significant improvements in InGaN/GaN nano-photoelectrodes for hydrogen generation by structure and polarization optimization.

Publications

Significant improvements in InGaN/GaN nano-photoelectrodes for hydrogen generation by structure and polarization optimization.

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