Advanced Characterization of 1 eV GaInAs Inverted Metamorphic Solar Cells (original) (raw)
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Temperature-dependent measurements of an inverted metamorphic multijunction (IMM) solar cell
2011 37th IEEE Photovoltaic Specialists Conference, 2011
The inverted metamorphic multijunction (IMM) solar cell has demonstrated efficiencies as high as 40.8% at 25°C and 326 suns concentration. The actual operating temperature in a commercial module, however, is likely to be as much as 50-70°C hotter, reaching as high as 100°C. In order to be able to evaluate the cell performance under these real-world operating conditions, we have measured the open-circuit voltage, short-circuit current density and efficiency at temperatures up to 125°C and concentrations up to 1000 suns, as well as the temperature coefficients of these parameters. Spectral response and one-sun current-voltage characteristics were measured by carefully adjusting the incident spectrum to selectively current-limit the different subcells. Concentrator measurements were taken on a pulsed solar simulator to minimize any additional heating due to the high intensity illumination. We compare our measured values to predictions based on detailed models of various triple junction solar cells. By choosing the optimum bandgaps for high temperature operation, the IMM can potentially result in greater energy production and lower temperature sensitivity under real operating conditions than a Ge-based solar cell.
Metamorphic and Lattice-Matched Solar Cells Under Concentration
2006 IEEE 4th World Conference on Photovoltaic Energy Conference, 2006
Metamorphic III-V semiconductor materials offer access to bandgaps that span key portions of the solar spectrum, enabling new bandgap combinations in multijunction solar cells, and increasing both theoretical and practical efficiency limits for terrestrial concentrator cells. Experimental results are given for the quantum efficiency of metamorphic GaInAs solar cells with bandgap from 1.1 to 1.4 eV, and for metamorphic GaInP with both ordered and disordered group-III sublattices. Variable intensity J sc vs. V oc measurements are used to compare recombination components due to n = 1 and n = 2 mechanisms in metamorphic and lattice-matched GaInAs, GaInP, and 3junction solar cells. A record efficiency metamorphic GaInP/ GaInAs/ Ge 3-junction solar cell has been produced with 38.8% efficiency independently confirmed (241 suns, AM1.5D, low-AOD, 25ºC), essentially equaling the performance of a lattice-matched 3-junction cell with 39.0% efficiency, the highest efficiency yet demonstrated and verified for a solar photovoltaic conversion device. With the combination of high-quality metamorphic materials that are increasingly less controlled by recombination at dislocations, and the higher efficiency limits afforded by freedom of lattice constant selection, practical terrestrial concentrator cell efficiencies well over 40% are expected in the near future.
Evidence of enhanced Zn-diffusion observed during the growth of Inverted Metamorphic Solar Cells
2019 IEEE 46th Photovoltaic Specialists Conference (PVSC)
Zinc-diffusion can induce multiple failures in the electrical performance of a multijunction solar cell. In this work, we show an important Zn-diffusion from the AlGaInP back-surface-field layer to the emitter of the GaInP top cell of an inverted multijunction solar cell. Through the analysis of different doping profiles, we provide strong evidence that the diffusion mechanism is (1) triggered by the growth of the tunnel junction cathode and (2) involves point defects. We analyze the implications of Zn-diffusion on the bandgap, the rear-passivation and the minority carrier quality of the GaInP solar subcell by relating the electrical performance of different samples to its corresponding doping profile.
Solar Energy Materials and Solar Cells, 2022
The growth of heavily doped tunnel junctions in inverted metamorphic multijunction solar cells induces a strong diffusion of Zn via a point-defects-assisted diffusion mechanism. The redistribution of Zn can compensate the n-type doping in the emitter of the GaInP top junction, degrading severely the conductivity of the whole solar cell and its conversion efficiency. This work evaluates different epitaxial growth strategies to achieve control on the [Zn] profile of an inverted metamorphic triple-junction structure, including: the reduction of the doping concentration in the tunnel junction to minimize the injection of point defects that trigger the diffusion mechanism; the use of different barrier layers to keep the injected point defects away from active layers and, finally, the minimization of Zn in the AlGaInP back-surface-field layer of the GaInP subcell. This last approach enables a high-conductivity multijunction solar cell device without redesigning the tunnel junction as well as a high electronic quality in the GaInP subcell, which shows a collection efficiency higher than 93% and an open-circuit-voltage offset of 410 mV at 1 sun irradiance. The characterization of final triple-junction devices, including quantum efficiency, electroluminescence, and light current-density-voltage curves at different irradiances, demonstrates a successful integration of all the subcell and tunnel junction components. This way, final solar cells with peak efficiencies exceeding 40 % at ~500 suns are demonstrated, despite using doping levels as low as 1•10 17 cm-3 in the AlGaInP:Zn back-surface-field of the GaInP subcell and using nonoptimized antireflective coatings.
Metamorphic Concentrator Solar Cells with Over 40% Conversion Efficiency
2007
Multijunction III-V concentrator cells have attracted much interest for concentrator photovoltaic (PV) systems recently due to their unparalleled conversion efficiencies. As high as these efficiencies are, they can be made even higher if the combination of subcell bandgaps for the multijunction solar cell are chosen from metamorphic semiconductors that are not all lattice-matched to the same growth substrate. Advances in the design of metamorphic subcells to reduce carrier recombination and increase voltage, wide-bandgap tunnel junctions capable of operating at high concentration, metamorphic buffers to transition from the substrate lattice constant to the active subcells, concentrator cell AR coating and grid design, and integration into 3-junction cells current matched under the terrestrial spectrum have resulted in new heights in solar cell performance. A metamorphic Ga0.44In0.56P/ Ga0.92In0.08As/ Ge 3-junction solar cell from this research has reached a record 40.7% efficiency a...
Development of inverted micromorph solar cells
This paper gives a comprehensive overview of the development of the amorphous silicon /microcrystalline silicon "Micromorph" tandem cell deposited in the inverted configuration (n-i-p/n-i-p). The objective of this work is to achieve a high stable efficiency (> 10 %) with an innovative cell structure, to be compatible with various types of substrates (including non-transparent or flexible substrates), while taking into account, at the same time, cost and ecological factors. In this context, ZnO conductive layers have been introduced as a replacement for ITO (Indium Tin Oxide) for both the top contact and the conducting back reflector. In a further important step towards potential cost reduction, high deposition rate of the bottom microcrystalline silicon cell has been thoroughly investigated. First results on complete structures show initial efficiencies up to 9.3 % on glass, aluminium and stainless steel substrates.
High-efficiency metamorphic GaInP/GaInAs/Ge solar cells grown by MOVPE
Journal of Crystal Growth, 2004
This paper focuses on the metal-organic vapor-phase epitaxy growth of 3-junction (3J) solar cells where the epitaxial Ga 0.44 In 0.56 P top and Ga 0.92 In 0.08 As middle subcells are grown lattice-mismatched on a Ge substrate. Single-junction metamorphic devices with 8% and 12%-In, GaInAs are grown on 100 mm dia. (0 0 1) Ge substrates and evaluated in comparison to approximately lattice-matched GaAs and Ga 0.99 In 0.01 As subcells. Layers are observed to be nearly 100% relaxed by high-resolution X-ray diffraction. Threading dislocation densities of B2 Â 10 5 cm À2 in the 8%-In layers are observed by electron beam induced current and cathodoluminescence. Single-junction devices show a constant offset between open-circuit voltage and bandgap of B380 mV. Building upon these results, 3J metamorphic Ga 0.44 In 0.56 P/ Ga 0.92 In 0.08 As/Ge solar cells are fabricated. Very high performances of small area devices are reported with 28.8% efficiency under the AM0 spectrum and 31.3% efficiency under the AM1.5G 1-sun terrestrial spectrum. r
Classification & Applicability of various metamaterials found to be promising in designing high efficiency solar cells. Also light absorption & polarization of electromagnetic energy have been found very prominent in case of metamaterials. Theoretical modeling of metamaterial solar cell has been developed in this study to achieve high efficiency. Hence, composite metamaterials have been investigated and metamaterial property like negative refractive index has been thoroughly studied. It has been found that if anti-reflective coating of solar cell is made of metamaterial, and its refractive index is 1 then no reflection occurs and the efficiency increases without any polarization effect. Also it has been realized that by using sawtooth structure in the second layer of metamaterial solar cell, the band gap can be tuned thus covering the whole solar spectrum and increasing efficiency. The simulation of the proposed model has been done utilizing PC1D, Wx AMPS and Matlab. Metamaterial solar cell shows promising future and this research work can be successfully used to design & develop metamaterial based highly efficient solar cells. Abstract-Classification & Applicability of various metamaterials found to be promising in designing high efficiency solar cells. Also light absorption & polarization of electromagnetic energy have been found very prominent in case of metamaterials. Theoretical modeling of metamaterial solar cell has been developed in this study to achieve high efficiency. Hence, composite metamaterials have been investigated and metamaterial property like negative refractive index has been thoroughly studied. It has been found that if anti-reflective coating of solar cell is made of metamaterial, and its refractive index is 1 then no reflection occurs and the efficiency increases without any polarization effect. Also it has been realized that by using sawtooth structure in the second layer of metamaterial solar cell, the band gap can be tuned thus covering the whole solar spectrum and increasing efficiency. The simulation of the proposed model has been done utilizing PC1D, Wx AMPS and Matlab. Metamaterial solar cell shows promising future and this research work can be successfully used to design & develop metamaterial based highly efficient solar cells.