Mingju Yang

High efficiency AlGaAs/Si monolithic tandem solar cell grown by metalorganic chemical vapor deposition

The improvements of the AlGaAs solar cell grown on the Si substrate and the AlGaAs/Si tandem solar cell by metalorganic chemical vapor deposition have been investigated. The active‐area conversion efficiency of the Al0.1Ga0.9As solar cell on the Si substrate as high as 12.9% has been obtained by improving the growth sequence and adopting an Al compositionally graded band emitter layer. A high efficiency monolithic AlGaAs/Si tandem solar cell with the active‐area conversion efficiency of 19.9% and 20.6% (AM0 and 1 sun at 27 °C) under two‐terminal and four‐terminal configurations, respectively, is demonstrated.

High-Efficiency Monolithic Three-Terminal GaAs/Si Tandem Solar Cells Fabricated by Metalorganic Chemical Vapor Deposition.

A monolithic GaAs/Si tandem solar cell which consists of a p + -n GaAs top cell and an n + -p-p + Si bottom cell is fabricated by metalorganic chemical vapor deposition. The conversion efficiency of the top cell is increased by improvement of the solar cell structure (adoption of a graded band emitter layer) and optimization of the growth conditions (increase of the thermal annealing temperature and the growth temperature). By combining the conversion efficiencies of the GaAs top cell (16.0%) and Si bottom cell (3.9%), the active-area conversion efficiency of 19.9% (AM0,1 sun) has been obtained in the three-terminal configuration.

Three-terminal monolithic cascade GaAs/Si solar cells

Abstract A three-terminal monolithic GaAs/Si cascade solar cell consisting of a p+-n GaAs top cell and an n+-p Si bottom cell is demonstrated in this paper. Layer (GBL) of AlxGa1−xAs between the Al0.8Ga0.2As window layer and the p-GaAs emitter layer, the quantum efficiency of the GaAs top cell has considerably been improved and the conversion efficiency of 15.1% (AM0, 27°C) has been achieved. The thermal-cycle annealing (TC) has been carried out to improve the quality of the GaAs film on Si. The effect of TC on the characteristics of the Si bottom cells has been investigated.

High efficiency AlGaAs/Si tandem solar cell over 20%

A high-efficiency AlGaAs/Si tandem solar cell is fabricated by metal-organic chemical vapor deposition (MOCVD). It consists of a Al/sub 0.15/Ga/sub 0.85/As top cell and a Si bottom cell. The crystalline quality of the Al/sub 0.15/Ga/sub 0.85/As heteroepitaxial layer grown on Si is improved using a high-temperature growth process (800/spl deg/C) and thermal cycle annealings (300/spl sim/900/spl deg/C). The quantum efficiency of the Si bottom cell in the long wavelength region is improved by back surface field. The conversion efficiencies of the tandem solar cell under AMO and 1 sun measurement conditions with 4-terminal and 2-terminal configuration are 20.0% and 19.0%, respectively. The conversion efficiencies of the tandem solar cell with graded-band-gap emitter Al/sub x/Ga/sub 1-x/As layer achieved 20.6% and 19.9% under same condition with 4-terminal and 2-terminal configuration, respectively.

AlxGa1-xAs/Si(x=0-0.22) Tandem Solar Cells Grown by Metalorganic Chemical Vapor Deposition.

Studies of Alx Ga1-x As/Si (x=0–0.22) tandem solar cells have been carried out by using metal organic chemical vapor deposition (MOCVD). The GaAs/Si tandem solar cell consists of a GaAs top cell with the Al0.3Ga0.7As buffer layer and a Si bottom cell with the n+-p-p+ structure. The theoretical analyses of the Si bottom cell are carried out for tandem solar cell application. The suitable resistivity of the p-Si substrate for the Si bottom cell has been found to be 10 Ω cm, which corresponds to the experimental results. The active-area conversion efficiency of 19.5% (1sun, AM0) for the GaAs/Si tandem solar cell has been achieved in the three-terminal configuration. In the case of the Alx Ga1-x As/Si tandem solar cell, x varies from 0.1 to 0.22. The crystalline quality of the Alx Ga1-x As heteroepitaxial layer grown on Si is improved, using a high-temperature growth process ( 800°C) and thermal cycle annealings ( 300–900°C). The active-area conversion efficiencies of 20.0% and 19.0% (1sun, AM0) for the Al0.15Ga0.85As/Si tandem solar cell are obtained with four-terminal and two-terminal configurations, respectively.

High Efficiency GaAs/Si Monolithic Three-Terminal Cascade Solar Cells Grown by Metal-Organic Chemical Vapor Deposition

A high-efficiency GaAs/Si monolithic three-terminal cascade solar cell is proposed and fabricated by the metal-organic chemical vapor deposition (MOCVD) method and thermal diffusion method. The quantum efficiency in the long wavelength region was improved by using p-Si substrates with the resistivity of 10 Ω cm as the Si bottom cells. Adopting a graded band-gap layer (GBL) of Alx Ga1-x As, the collection efficiency of the GaAs top cell was increased considerably. A total conversion efficiency of 19.1% was achieved at the AM0 condition for the GaAs/Si three-terminal cascade solar cell.

High efficiency monolithic GaAs/Si tandem solar cells grown by MOCVD

A monolithic high-efficiency GaAs/Si cascade solar cell fabricated by MOCVD is demonstrated. It consists of the GaAs top cell and the Si bottom cell. Using a buffer layer of Al/sub 0.3/Ga/sub 0.7/As, the conversion efficiency of the GaAs top cell is decreased from 15.1% from 14.2%, but it makes the efficiency of the Si bottom cell increased from 4.3% to 5.3%. The theoretical analyses of the Si bottom cell are carried out. The suitable resistivity of p-Si substrate for the Si bottom cell is founded to be 10 /spl Omega//spl middot/cm, which corresponded with the experimental results. The total conversion efficiency of the GaAs/Si tandem solar cell is 19.5% (1 sun, AM0) which has been achieved in a three-terminal configuration.

Time-resolved photoluminescence characterization of GaAs and AlGaAs on Si substrate grown by MOCVD

Abstract GaAs layers and AlGaAs solar cells grown on Si substrates have been characterized by time-resolved photoluminescence (TRP). The effects of the growth temperature, the strained layer superlattice (SLS), and the thermal cycle annealing (TCA) on the TRP characteristics are discussed. The minority carrier lifetime is increased with increasing growth temperature and by using SLS + TCA. The longest minority carrier lifetime of GaAs on Si obtained in this study is 0.50 ns.

Integrated wavelength-division photosensor using GaAs on Si

Abstract A new wavelength-division photosensor using AlGaAs on Si grown by MOCVD has been developed. The photosensor is made up of a top sensor consisting of an AlGaAs photodiode and a bottom sensor consisting of an Si photodiode. The normalized difference of output currents of the top and bottom sensors has a good linear relationship with the wavelength of incident monochromatic light from 600 to 880 nm. The sensitivity and operating wavelength region of the sensor can easily be varied by changing the thickness and the Al content of the top sensor.

Improvement of AlGaAs solar cell grown on Si substrate

The improvement of Al/sub 0.1/Ga/sub 0.9/As solar cell grown on Si substrate by metalorganic chemical vapor deposition has been described in this paper. The conversion efficiency as high as 12.9% has been obtained by employing the high growth temperature, the high annealing temperature during the growth, the long hold time at the annealing temperature and graded band emitter layer. A novel technique to reduce the stress of GaAs grown on Si is demonstrated. GaAs was grown on Si with GaSb intermediate layer, followed by the laser pulse irradiation (wavelength is 1.064 mm, the pulse width is 140 ps and pulse energy is 40 mJ/pulse). The stress of GaAs on Si with 10 laser shots is one-fourth of that before laser irradiation. The stress-relaxed AlGaAs solar cell structure on Si is proposed.