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Materials|20 Article(s)
Effect of temperature on the electronic, optical, mechanical characteristics, phonon frequencies, and sound velocities of GaP
Al Maaitah Ibtisam F
We report a theoretical analysis of the electronic, optical, and mechanical properties of zinc-blende GaP semiconductor material. High-temperature impact on the interesting features has been reported. The temperature dependence of sound velocity and phonon frequencies of GaP has been determined. The pseudopotential technique has been used in our study. The current study can help in our comprehension of how temperature affects the electronic characteristics of GaP material. Our findings show generally a good accordance with the experiment. The prediction properties could be used in optoelectronic applications in the high-temperature range. We report a theoretical analysis of the electronic, optical, and mechanical properties of zinc-blende GaP semiconductor material. High-temperature impact on the interesting features has been reported. The temperature dependence of sound velocity and phonon frequencies of GaP has been determined. The pseudopotential technique has been used in our study. The current study can help in our comprehension of how temperature affects the electronic characteristics of GaP material. Our findings show generally a good accordance with the experiment. The prediction properties could be used in optoelectronic applications in the high-temperature range.
Optoelectronics Letters
- Publication Date: Jan. 01, 2023
- Vol. 19, Issue 1, 31 (2023)
Tuning zinc doping content to optimize optical and structural properties of Cd1-xZnxS buffer layers
Xin XIE, Yuming XUE, Chaoqun LU, Yifan WANG, Binbin WEN, and Jiangchao and WANG
In this paper, Cd1-xZnxS thin films were prepared by chemical bath deposition (CBD), and the effects of different zinc doping content on the morphological structure and optical properties of Cd1-xZnxS buffer layers are systematically discussed. The experimental results show that in the deposition process of different substrates, the crystal structure of the film is all hexagonal, and when the concentration of zinc sulfate (ZnSO4) precursor is varied from 0 to 0.025 M, the films are uniform and dense. With the increase of zinc content, the X-ray diffraction (XRD) peak of the films shifted behind that of CdS film (002). It showed 70% to 90% transmittance in the visible region and the optical band gap increased gradually. The band gap value of the films obtained ranged from 2.43 eV to 3.01 eV. It shows the potential feasibility of its application to photovoltaic devices. In this paper, Cd1-xZnxS thin films were prepared by chemical bath deposition (CBD), and the effects of different zinc doping content on the morphological structure and optical properties of Cd1-xZnxS buffer layers are systematically discussed. The experimental results show that in the deposition process of different substrates, the crystal structure of the film is all hexagonal, and when the concentration of zinc sulfate (ZnSO4) precursor is varied from 0 to 0.025 M, the films are uniform and dense. With the increase of zinc content, the X-ray diffraction (XRD) peak of the films shifted behind that of CdS film (002). It showed 70% to 90% transmittance in the visible region and the optical band gap increased gradually. The band gap value of the films obtained ranged from 2.43 eV to 3.01 eV. It shows the potential feasibility of its application to photovoltaic devices.
Optoelectronics Letters
- Publication Date: Jan. 01, 2023
- Vol. 19, Issue 1, 25 (2023)
Steady state multiple dark spatial solitons in the biased photorefractive-photovoltaic crystals
Yu-hong ZHANG, Wei SU, Cun-li DUAN, and Ai-ling TIAN
We theoretically study the evolution of dark solitons in the biased photorefractive-photovoltaic crystal by using beam propagation method (BPM). We find that when the absolute value of the extra bias field is less than the photovoltaic field, the dark screening-photovoltaic (SP) solitons can be observed. The initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an sequence of dark coherent solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. When the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark solitons, which re-alizes a progressive transition from the low-order solitons to a sequence of higher-order solitons. We theoretically study the evolution of dark solitons in the biased photorefractive-photovoltaic crystal by using beam propagation method (BPM). We find that when the absolute value of the extra bias field is less than the photovoltaic field, the dark screening-photovoltaic (SP) solitons can be observed. The initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an sequence of dark coherent solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. When the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark solitons, which re-alizes a progressive transition from the low-order solitons to a sequence of higher-order solitons.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 367 (2018)
The impact of Al2O3 back interface layer on low-temperature growth of ultrathin Cu(In,Ga)Se2 solar cells
Yang LIU, Wei LIU, Meng-xin CHEN, Si-han SHI, Zhi-chao HE, Jin-long GONG, Tuo WANG, Zhi-qiang ZHOU, Fang-fang LIU, Yun SUN, and Shu XU
With reducing the absorber layer thickness and processing temperature, the recombination at the back interface is se-vere, which both can result in the decrease of open-circuit voltage and fill factor. In this paper, we prepare Al2O3 by atomic layer deposition (ALD), and investigate the effect of its thickness on the performance of Cu(In,Ga)Se2 (CIGS) solar cell. The device recombination activation energy (EA) is increased from 1.04 eV to 1.11 eV when the thickness of Al2O3 is varied from 0 nm to 1 nm, and the height of back barrier is decreased from 48.54 meV to 38.05 meV. An effi-ciency of 11.57 % is achieved with 0.88-μm-thick CIGS absorber layer. With reducing the absorber layer thickness and processing temperature, the recombination at the back interface is se-vere, which both can result in the decrease of open-circuit voltage and fill factor. In this paper, we prepare Al2O3 by atomic layer deposition (ALD), and investigate the effect of its thickness on the performance of Cu(In,Ga)Se2 (CIGS) solar cell. The device recombination activation energy (EA) is increased from 1.04 eV to 1.11 eV when the thickness of Al2O3 is varied from 0 nm to 1 nm, and the height of back barrier is decreased from 48.54 meV to 38.05 meV. An effi-ciency of 11.57 % is achieved with 0.88-μm-thick CIGS absorber layer.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 363 (2018)
Mechanism of the UV band-edge photorefractivity en-hancement in near-stoichiometric LiNbO3
Fei-fei XIN
The UV photorefractive properties of near-stoichiometric LiNbO3 single crystal are found to be significantly enhanced com-pared with the congruent one at 325 nm. The temperature dependence of the band edge of near-stoichiometric LiNbO3 crystal is investigated. Significant thermal-induced spectral shift in band gap which obeys the Bose-Einstein expression is observed, and the fundamental band gap at zero absolute temperature is found to be much larger than the congruent one. New absorp-tion bands near the UV band edge which are much stronger in the near-stoichiometric LiNbO3 than those in the congruent LiNbO3 crystal show up at temperatures lower than ~400 K. Note that the UV photorefractivity is enhanced in SLN, which has exactly the same tendency as the absorption strength. The UV photorefractive properties of near-stoichiometric LiNbO3 single crystal are found to be significantly enhanced com-pared with the congruent one at 325 nm. The temperature dependence of the band edge of near-stoichiometric LiNbO3 crystal is investigated. Significant thermal-induced spectral shift in band gap which obeys the Bose-Einstein expression is observed, and the fundamental band gap at zero absolute temperature is found to be much larger than the congruent one. New absorp-tion bands near the UV band edge which are much stronger in the near-stoichiometric LiNbO3 than those in the congruent LiNbO3 crystal show up at temperatures lower than ~400 K. Note that the UV photorefractivity is enhanced in SLN, which has exactly the same tendency as the absorption strength.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 359 (2018)
Optical properties of Cr3+ doped Na5Lu9F32 single crystals grown by the Bridgman method
Zhi-wei ZHAO, Hai-ping XIA, Jian-xu HU, Jian-li ZHANG, Yong-sheng ZHU, and Bao-jiu (陈宝玖)3 and CHEN
The growth of Na5Lu9F32 single crystals doped with Cr3+ ions in 0.1 mol%, 0.2 mol% and 0.5 mol% concentrations by Bridgman method was reported. The optical absorption and luminescence spectra decisively demonstrate that the Cr dopant enters Na5Lu9F32 as Cr3+. Fluorescence emission at wavelengths of 418 nm, 444 nm, 653 nm and 678 nm can be observed under the excitation of 372 nm and the fluorescence lifetime at 418 nm was measured to be ~10.31 μs. The possible crystal sites for Cr3+ ions in Na5Lu9F32 single crystal were discussed, and the lattice parameter Dq, Racach parameters B and C were estimated. The growth of Na5Lu9F32 single crystals doped with Cr3+ ions in 0.1 mol%, 0.2 mol% and 0.5 mol% concentrations by Bridgman method was reported. The optical absorption and luminescence spectra decisively demonstrate that the Cr dopant enters Na5Lu9F32 as Cr3+. Fluorescence emission at wavelengths of 418 nm, 444 nm, 653 nm and 678 nm can be observed under the excitation of 372 nm and the fluorescence lifetime at 418 nm was measured to be ~10.31 μs. The possible crystal sites for Cr3+ ions in Na5Lu9F32 single crystal were discussed, and the lattice parameter Dq, Racach parameters B and C were estimated.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 355 (2018)
Frequency offset estimation in the intermediate fre-quency for satellite-based AIS signals
Xin MENG, She-xiang MA, Chen LIU, and Jian-fu TENG
In this paper, an accurate frequency offset estimator is investigated in the intermediate frequency for the satellite-based automatic identification system (AIS) signals. Using Gaussian minimum shift keying (GMSK) modulation for trans-mission, the AIS signal is shown to be a plane wave with the modulated phase information and carrier frequency re-sulting from the Doppler effects. Hence, the phase information can be eliminated with a re-modulated signal, and the frequency offset can be estimated by the ratio of the maximum spectral amplitude and its neighbor spectral amplitude based on the fast Fourier transformation (FFT) interpolation. The estimator has low complexity, and it is easy to im-plement. Computer simulations are used to assess the performance of the estimator. In this paper, an accurate frequency offset estimator is investigated in the intermediate frequency for the satellite-based automatic identification system (AIS) signals. Using Gaussian minimum shift keying (GMSK) modulation for trans-mission, the AIS signal is shown to be a plane wave with the modulated phase information and carrier frequency re-sulting from the Doppler effects. Hence, the phase information can be eliminated with a re-modulated signal, and the frequency offset can be estimated by the ratio of the maximum spectral amplitude and its neighbor spectral amplitude based on the fast Fourier transformation (FFT) interpolation. The estimator has low complexity, and it is easy to im-plement. Computer simulations are used to assess the performance of the estimator.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 4, 301 (2018)
Performance analysis of multiuser diversity scheduling schemes in FSO communication system
Tao LIU, Hai-lin ZHANG, Hui-hua FU, Ping WANG, and Nan XIANG
Taking into consideration the aperture averaging, the system performance of a point-to-multipoint free space optical (FSO) system for various multiuser diversity scheduling schemes is studied over exponentiated Weibull (EW) fading channels. The selection principles of greedy scheduling (GS), selective multiuser diversity scheduling (SMDS), proportional fair scheduling (PFS) and selective multiuser diversity scheduling with exponential rule (SMDS-ER) schemes are introduced and compared on the basis of time-varying behavior of turbulence channel fading in the present system. The analytical average capacity ex-pressions for the GS and SMDS schemes are derived, respectively. Then, the relative capacity simulations for PFS and SMDS-ER schemes are also provided over EW fading channels with the binary phase shift keying (BPSK) modulation. The results show that the GS scheme obtains the maximum average capacity at the cost of the fairness of users. The SMDS-ER receives the minimum capacity, but it guarantees the fairness of users. The SMDS and PFS schemes can get balance between capacity and fairness. This study can be used for FSO system design. Taking into consideration the aperture averaging, the system performance of a point-to-multipoint free space optical (FSO) system for various multiuser diversity scheduling schemes is studied over exponentiated Weibull (EW) fading channels. The selection principles of greedy scheduling (GS), selective multiuser diversity scheduling (SMDS), proportional fair scheduling (PFS) and selective multiuser diversity scheduling with exponential rule (SMDS-ER) schemes are introduced and compared on the basis of time-varying behavior of turbulence channel fading in the present system. The analytical average capacity ex-pressions for the GS and SMDS schemes are derived, respectively. Then, the relative capacity simulations for PFS and SMDS-ER schemes are also provided over EW fading channels with the binary phase shift keying (BPSK) modulation. The results show that the GS scheme obtains the maximum average capacity at the cost of the fairness of users. The SMDS-ER receives the minimum capacity, but it guarantees the fairness of users. The SMDS and PFS schemes can get balance between capacity and fairness. This study can be used for FSO system design.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 4, 296 (2018)
Influence of annealing temperature on visible-light photocatalytic activities of Ag3PO4 particulates synthe-sized using CH3COOAg as a precursor
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Ag3PO4 microparticles (MPs) were prepared through a facile chemical precipitation route and using silver acetate (AgAc) as metal salt. The effect of annealing temperature (Ta) and time (τa) on the actual photocatalytic (PC) activity of Ag3PO4 MPs is investigated. The optimal annealing parameters are Ta of 400 °C and τa of 90 min. The enhanced PC activity by annealing at 400 °C is ascribed to the increase of electron mobility. Besides, an Ag3PO4 photoelectrode was fabricated through a drop-coating deposition route, which demonstrates a photocurrent density of 80 μA/cm2 and ac-ceptable stability. The n-type conduction behavior of Ag3PO4 is verified by a Mott-Schottky (M-S) plot. Ag3PO4 microparticles (MPs) were prepared through a facile chemical precipitation route and using silver acetate (AgAc) as metal salt. The effect of annealing temperature (Ta) and time (τa) on the actual photocatalytic (PC) activity of Ag3PO4 MPs is investigated. The optimal annealing parameters are Ta of 400 °C and τa of 90 min. The enhanced PC activity by annealing at 400 °C is ascribed to the increase of electron mobility. Besides, an Ag3PO4 photoelectrode was fabricated through a drop-coating deposition route, which demonstrates a photocurrent density of 80 μA/cm2 and ac-ceptable stability. The n-type conduction behavior of Ag3PO4 is verified by a Mott-Schottky (M-S) plot.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 4, 291 (2018)
Buffer-modified C60/pentacene as organic charge gen-eration layer based on Al and MoO3
Zhen WANG, Fei LIU, Ai CHEN, Jia-feng XIE, and Wei-zhong CHEN
We demonstrate tandem organic light-emitting diodes (TOLEDs) with excellent performance using Al and MoO3 buffer-modified C60/pentacene as charge generation layer (CGL). Al and MoO3 were used as the electron and hole in-jection layers of C60/pentacene CGL, respectively. Green phosphorescence TOLEDs with the structure of ITO/NPB/mCP:Ir(ppy)3/TPBi/Al/C60/pentacene/MoO3/NPB/mCP:Ir(ppy)3/TPBi/Cs2CO3/Al were fabricated. The re-sults show that the inserted Al and MoO3 can effectively increase the charge injection capacity of organic CGL, re-sulting the improvement of luminance and current efficiency of TOLEDs. The turn-on voltage of TOLEDs is much lower than that of single-unit device, and the current efficiency is more than 2 times larger than that of the single-unit device. TOLEDs can exhibit excellent photoelectric performance when the thicknesses of Al, C60, pentacene and MoO3 are 3 nm, 15 nm, 25 nm and 1 nm, respectively. The maximum luminance and current efficiency are 7 920.0 cd/m2 and 16.4 cd/A, respectively. This work is significant to build new CGL structures for realizing high-performance TOLEDs. We demonstrate tandem organic light-emitting diodes (TOLEDs) with excellent performance using Al and MoO3 buffer-modified C60/pentacene as charge generation layer (CGL). Al and MoO3 were used as the electron and hole in-jection layers of C60/pentacene CGL, respectively. Green phosphorescence TOLEDs with the structure of ITO/NPB/mCP:Ir(ppy)3/TPBi/Al/C60/pentacene/MoO3/NPB/mCP:Ir(ppy)3/TPBi/Cs2CO3/Al were fabricated. The re-sults show that the inserted Al and MoO3 can effectively increase the charge injection capacity of organic CGL, re-sulting the improvement of luminance and current efficiency of TOLEDs. The turn-on voltage of TOLEDs is much lower than that of single-unit device, and the current efficiency is more than 2 times larger than that of the single-unit device. TOLEDs can exhibit excellent photoelectric performance when the thicknesses of Al, C60, pentacene and MoO3 are 3 nm, 15 nm, 25 nm and 1 nm, respectively. The maximum luminance and current efficiency are 7 920.0 cd/m2 and 16.4 cd/A, respectively. This work is significant to build new CGL structures for realizing high-performance TOLEDs.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 4, 286 (2018)
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