Matching Items (7)
Description
A CdZnTe/MgCdTe double-heterostructure (DH) consisting of a 3 μm thick Cd0.9946 Zn0.0054Te middle layer that is lattice-matched to an InSb substrate has been grown using molecular beam epitaxy. A long carrier lifetime of 3.4 × 102 ns has been demonstrated at room temperature, which is approximately three times as long as that of a CdTe/MgCdTe DH with identical layer thickness. This substantial improvement is due to the reduction in misfit dislocation density in the CdZnTe alloy. In contrast, a CdTe/MgCdTe DH with 3 μm thick CdTe layer grown on an InSb substrate exhibits a strain relaxation of ∼30%, which leads to a wider x-ray diffraction peak, a weaker integrated photoluminescence intensity, and a shorter minority carrier lifetime of 1.0 × 102 ns. These findings indicate that CdZnTe lattice-matched to InSb has great potential as applied to high-efficiency solar cells as well as virtual substrates for high-performance large-area HgCdTe focal plane arrays.
ContributorsLiu, Shi (Author) / Zhao, Xin-Hao (Author) / Campbell, Calli (Author) / DiNezza, Michael J. (Author) / Zhao, Yuan (Author) / Zhang, Yong-Hang (Author) / Ira A. Fulton Schools of Engineering (Contributor)
Created2015-01-01
ContributorsLiu, Shi (Author) / Zhao, Xin-Hao (Author) / Campbell, Calli M. (Author) / DiNezza, Michael J. (Author) / Zhao, Yuan (Author) / Zhang, Yong-Hang (Author)
Created2015
ContributorsZhao, Xin-Hao (Author) / DiNezza, Michael J. (Author) / Liu, Shi (Author) / Campbell, Calli M. (Author) / Zhao, Yuan (Author) / Zhang, Yong-Hang (Author)
Created2014
ContributorsZhao, Xin-Hao (Author) / DiNezza, Michael J. (Author) / Liu, Shi (Author) / Lin, Su (Author) / Zhao, Yuan (Author) / Zhang, Yong-Hang (Author)
Created2014
ContributorsBückers, C. (Author) / Blume, G (Author) / Thränhardt, A. (Author) / Schlichenmaier, C. (Author) / Klar, P. J. (Author) / Weiser, G. (Author) / Koch, S. W. (Author) / Hader, J. (Author) / Moloney, J. V. (Author) / Hosea, T. J. C. (Author) / Sweeney, S. J. (Author) / Wang, J.-B. (Author) / Johnson, Shane R. (Author) / Zhang, Yong-Hang (Author)
Created2007
ContributorsHorst, S. (Author) / Chatterjee, S. (Author) / Hantke, K. (Author) / Klar, P. J. (Author) / Nemeth, I. (Author) / Stolz, W. (Author) / Volz, K. (Author) / Bückers, C. (Author) / Thränhardt, A. (Author) / Koch, S. W. (Author) / Rühle, W. (Author) / Johnson, Shane R. (Author) / Wang, J.-B. (Author) / Zhan, Yong-Hang (Author)
Created2008
Description
Cadmium Telluride (CdTe) possesses preferable optical properties for photovoltaic (PV) applications: a near optimum bandgap of 1.5 eV, and a high absorption coefficient of over 15,000 cm-1 at the band edge. The detailed-balance limiting efficiency is 32.1% with an open-circuit voltage (Voc) of 1.23 V under the AM1.5G spectrum. The record polycrystalline CdTe thin-film cell efficiency has reached 22.1%, with excellent short-circuit current densities (Jsc) and fill-factors (FF). However, the Voc (~900 mV) is still far below the theoretical value, due to the large non-radiative recombination in the polycrystalline CdTe absorber, and the low-level p-type doping.
Monocrystalline CdTe/MgCdTe double-heterostructures (DHs) grown on lattice-matched InSb substrates have demonstrated impressively long carrier lifetimes in both unintentionally doped and Indium-doped n-type CdTe samples. The non-radiative recombination inside of, and at the interfaces of the CdTe absorbers in CdTe/MgCdTe DH samples has been significantly reduced due to the use of lattice-matched InSb substrates, and the excellent passivation provided by the MgCdTe barrier layers. The external luminescent quantum efficiency (η_ext) of n-type CdTe/MgCdTe DHs is up to 3.1%, observed from a 1-µm-thick CdTe/MgCdTe DH doped at 1017 cm-3. The 3.1% η_ext corresponds to an internal luminescent quantum efficiency (η_int) of 91%. Such a high η_ext gives an implied Voc, or quasi-Fermi-level splitting, of 1.13 V.
To obtain actual Voc, the quasi-Fermi-level splitting should be extracted to outside the circuit using a hole-selective contact layer. However, CdTe is difficult to be doped p-type, making it challenging to make efficient PN junction CdTe solar cells. With the use of MgCdTe barrier layers, the hole-contact layer can be defective without affecting the voltage. P-type hydrogenated amorphous silicon is an effective hole-selective contact for CdTe solar cells, enabling monocrystalline CdTe/MgCdTe DH solar cells to achieve Voc over 1.1 V, and a maximum active area efficiency of 18.8% (Jsc = 23.3 mA/cm2, Voc = 1.114 V, and FF = 72.3%). The knowledge gained through making the record-efficiency monocrystalline CdTe cell, particularly the n-type doping and the double-heterostructure design, may be transferable to polycrystalline CdTe thin-film cells and improve their competitiveness in the PV industry.
Monocrystalline CdTe/MgCdTe double-heterostructures (DHs) grown on lattice-matched InSb substrates have demonstrated impressively long carrier lifetimes in both unintentionally doped and Indium-doped n-type CdTe samples. The non-radiative recombination inside of, and at the interfaces of the CdTe absorbers in CdTe/MgCdTe DH samples has been significantly reduced due to the use of lattice-matched InSb substrates, and the excellent passivation provided by the MgCdTe barrier layers. The external luminescent quantum efficiency (η_ext) of n-type CdTe/MgCdTe DHs is up to 3.1%, observed from a 1-µm-thick CdTe/MgCdTe DH doped at 1017 cm-3. The 3.1% η_ext corresponds to an internal luminescent quantum efficiency (η_int) of 91%. Such a high η_ext gives an implied Voc, or quasi-Fermi-level splitting, of 1.13 V.
To obtain actual Voc, the quasi-Fermi-level splitting should be extracted to outside the circuit using a hole-selective contact layer. However, CdTe is difficult to be doped p-type, making it challenging to make efficient PN junction CdTe solar cells. With the use of MgCdTe barrier layers, the hole-contact layer can be defective without affecting the voltage. P-type hydrogenated amorphous silicon is an effective hole-selective contact for CdTe solar cells, enabling monocrystalline CdTe/MgCdTe DH solar cells to achieve Voc over 1.1 V, and a maximum active area efficiency of 18.8% (Jsc = 23.3 mA/cm2, Voc = 1.114 V, and FF = 72.3%). The knowledge gained through making the record-efficiency monocrystalline CdTe cell, particularly the n-type doping and the double-heterostructure design, may be transferable to polycrystalline CdTe thin-film cells and improve their competitiveness in the PV industry.
ContributorsZhao, Yuan (Author) / Zhang, Yong-Hang (Thesis advisor) / Bertoni, Mariana (Committee member) / King, Richard (Committee member) / Holman, Zachary (Committee member) / Arizona State University (Publisher)
Created2016