Semiconductor nanowire （NW） solar cells with a single p-n junction have exhibited efficiency comparable to that of their planar counterparts with a substantial reduction in material consumption. Tandem geometry is a...Semiconductor nanowire （NW） solar cells with a single p-n junction have exhibited efficiency comparable to that of their planar counterparts with a substantial reduction in material consumption. Tandem geometry is a path toward the fabrication of devices with even higher efficiencies, for which a key step is the fabrication of tunnel （Esaki） diodes within NWs with the correct diameter, pitch, and material combination for maximized efficiency. InP/GaInP and GaInP/InP NW tunnel diodes with band gap combinations corresponding to high-efficiency solar energy harvesting were fabricated and their electrical characteristics and material properties were compared. Four different configurations, with respect to material composition and doping, were investigated. The NW arrays were grown with metal-organic vapor-phase epitaxy from Au particles by use of nano-imprint lithography, metal evaporation and lift-off. Electrical measurements showed that the NWs behave as tunnel diodes in both InP （bottom）/GaInP （top） and GaInP （bottom）/InP （top） configurations, exhibiting a maximum peak current density of 25 A/cm^2, and maximum peak to valley current ratio of 2.5 at room temperature. The realization of NW tunnel diodes in both InP/GaInP and GaInP/InP configurations represent an opportunity for the use of NW tandem solar cells, whose efficiency is independent of the growth order of the different materials, increasing the flexibility regarding dopant incorporation polarity.展开更多
CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work,...CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work, highly disordered GaInP with high crystalline quality was obtained by optimizing growth conditions. Room- temperature and low-temperature photoluminescence （PL） spectra of A1GalnP/GaInP/A1GaInP double heterostruc- tures （DHs） reveal that the band edge emission intensity is enhanced by optimizing growth temperature, V/III ratio, and reactor pressure at the expense of low energy peak originating from spatially indirect recombination due to the ordering-related defects. The DH sample with less ordering-related defects demonstrates a longer effective minority carrier lifetime, consequently, the GaInP solar cell shows a significant improvement in the performance.展开更多
As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin...As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.展开更多
GaInP and AlGaInP solar cells were grown by metal organic chemical vapor deposition（MOCVD）, and theoretical analysis demonstrated that hetero-interface recombination velocity plays an important role in the optimizin...GaInP and AlGaInP solar cells were grown by metal organic chemical vapor deposition（MOCVD）, and theoretical analysis demonstrated that hetero-interface recombination velocity plays an important role in the optimizing of cell performance, especially the interface between base layer and back surface field（BSF）. Measurements including lattice-matched growth and pseudo-BSF were taken to optimize BSF design. Significant improvement of Vocin GaInP and AlGaInP solar cells imply that the measures we took are effective and promising for performance improvement in the next generation high efficiency solar cells.展开更多
GaInP alloy could be the most trusted key material for fabricating super-high-efficiency single-and multijunction solar cells, especially for space applications. The storage and transfer of optical excitation energy i...GaInP alloy could be the most trusted key material for fabricating super-high-efficiency single-and multijunction solar cells, especially for space applications. The storage and transfer of optical excitation energy in this key alloy is thus a key subject of the energy conversion from optical to electrical. In this article we present a study of the subject through investigating photoluminescence(PL) degradation in the GaInP epilayer at 4 K under the continuous optical excitations of ultraviolet(UV) 325 nm, visible 488.0 and 514.5 nm lasers. It is found that the decline of PL intensity with the irradiation time may be represented by I(t)/I0=(1 + tτ-1)-1+C, where I0 is the luminescence intensity at the beginning of irradiation, a time constant, and C a background. Moreover, the PL degradation degree reduces with increasing the excitation wavelength. In addition, some red shift of the PL peak is observed accompanying with the intensity decline under the UV laser excitation. These PL signatures indicate that the localized carriers within the local atomic ordering domains play a major role in the storage and transfer of the excitation energy via photon recycling processes.展开更多
文摘Semiconductor nanowire （NW） solar cells with a single p-n junction have exhibited efficiency comparable to that of their planar counterparts with a substantial reduction in material consumption. Tandem geometry is a path toward the fabrication of devices with even higher efficiencies, for which a key step is the fabrication of tunnel （Esaki） diodes within NWs with the correct diameter, pitch, and material combination for maximized efficiency. InP/GaInP and GaInP/InP NW tunnel diodes with band gap combinations corresponding to high-efficiency solar energy harvesting were fabricated and their electrical characteristics and material properties were compared. Four different configurations, with respect to material composition and doping, were investigated. The NW arrays were grown with metal-organic vapor-phase epitaxy from Au particles by use of nano-imprint lithography, metal evaporation and lift-off. Electrical measurements showed that the NWs behave as tunnel diodes in both InP （bottom）/GaInP （top） and GaInP （bottom）/InP （top） configurations, exhibiting a maximum peak current density of 25 A/cm^2, and maximum peak to valley current ratio of 2.5 at room temperature. The realization of NW tunnel diodes in both InP/GaInP and GaInP/InP configurations represent an opportunity for the use of NW tandem solar cells, whose efficiency is independent of the growth order of the different materials, increasing the flexibility regarding dopant incorporation polarity.
基金Project supported by the National Natural Science Foundation of China(No.61376065)the Suzhou Science and Technology Project(No.ZXG2013044)
文摘CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work, highly disordered GaInP with high crystalline quality was obtained by optimizing growth conditions. Room- temperature and low-temperature photoluminescence （PL） spectra of A1GalnP/GaInP/A1GaInP double heterostruc- tures （DHs） reveal that the band edge emission intensity is enhanced by optimizing growth temperature, V/III ratio, and reactor pressure at the expense of low energy peak originating from spatially indirect recombination due to the ordering-related defects. The DH sample with less ordering-related defects demonstrates a longer effective minority carrier lifetime, consequently, the GaInP solar cell shows a significant improvement in the performance.
基金supported by the National Natural Science Foundation of China (Grant No. 60706014)the National Science Fund for Distinguished Young Scholars (Grant No. 60625302)+2 种基金the National Natural Science Foundation of China (General Program) (Grant No. 2009CB320603)the National High-Tech Research and Development Program of China (Grant No. 2009AA04Z159)the Shanghai Leading Academic Discipline Project (Grant No. B504)
文摘As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.
基金Project supported by the National Natural Science Foundation of China (No. 61474076)
文摘GaInP and AlGaInP solar cells were grown by metal organic chemical vapor deposition（MOCVD）, and theoretical analysis demonstrated that hetero-interface recombination velocity plays an important role in the optimizing of cell performance, especially the interface between base layer and back surface field（BSF）. Measurements including lattice-matched growth and pseudo-BSF were taken to optimize BSF design. Significant improvement of Vocin GaInP and AlGaInP solar cells imply that the measures we took are effective and promising for performance improvement in the next generation high efficiency solar cells.
基金supported by the National Natural Science Foundation of China (Grant No. 11374247)in part by a grant from the University Grants Committee Areas of Excellence Scheme of the Hong Kong Special Administrative Region, China (Project No. [AoE/P-03/08])
文摘GaInP alloy could be the most trusted key material for fabricating super-high-efficiency single-and multijunction solar cells, especially for space applications. The storage and transfer of optical excitation energy in this key alloy is thus a key subject of the energy conversion from optical to electrical. In this article we present a study of the subject through investigating photoluminescence(PL) degradation in the GaInP epilayer at 4 K under the continuous optical excitations of ultraviolet(UV) 325 nm, visible 488.0 and 514.5 nm lasers. It is found that the decline of PL intensity with the irradiation time may be represented by I(t)/I0=(1 + tτ-1)-1+C, where I0 is the luminescence intensity at the beginning of irradiation, a time constant, and C a background. Moreover, the PL degradation degree reduces with increasing the excitation wavelength. In addition, some red shift of the PL peak is observed accompanying with the intensity decline under the UV laser excitation. These PL signatures indicate that the localized carriers within the local atomic ordering domains play a major role in the storage and transfer of the excitation energy via photon recycling processes.
