Inverted Metamorphic Research Articles

Defects analysis of radiation damage mechanism for IMM triple-junction solar cell under 1 MeV electron irradiation

Inverted metamorphic (IMM) GaInP/GaAs/InGaAs rigid triple-junction solar cells under 1 MeV electron irradiation at various fluences were investigated theoretically. By fitting the electrical and optical parameters of solar cells with experimental results at the fluence ranging from 1 × 1014 e cm−2 to 1 × 1015 e cm−2, basic trap information was obtained, and then the minority carrier lifetime and trap concentration of sub-cells at various fluences were also calculated. The defects analysis of IMM triple-junction solar cell presented in this work could help understanding the radiation damage mechanism of 1 MeV electron irradiation.

Advanced Characterization of 1 eV GaInAs Inverted Metamorphic Solar Cells

In this work, 1 eV Ga0.7In0.3As inverted metamorphic (IMM) solar cells were analyzed to achieve a deeper understanding of the mechanism limiting their improvement. For this purpose, high-resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM), high-resolution cross-sectional cathodoluminescence (CL), and transient in situ surface reflectance were carried out. Additionally, the photovoltaic responses of the complete devices were measured using the external quantum efficiency (EQE) and numerically simulated through Silvaco TCAD ATLAS. The combination of structural characterization of the semiconductor layers and measurements of the solar cell photovoltaic behavior, together with device modeling, allows us to conclude that the lifetime of the bulk minority carriers is the limiting factor influencing the PV response since the recombination at the interfaces (GaInP window–GaInAs emitter and GaInAs base–GaInP back surface field (BSF)) does not impact the carrier recombination due to the favorable alignment between the conduction and the valance bands. The advanced characterization using cross-sectional cathodoluminescence, together with transient in situ surface reflectance, allowed the rejection of the formation of traps related to the GaInAs growth conditions as being responsible for the decrement in the minority-carrier lifetime. Conversely, the TEM and HRXRD revealed that the presence of misfit dislocations in the GaInAs layer linked to strain relaxation, which were probably formed due to an excessive tensile strain in the virtual substrate or an incorrect combination of alloy compositions in the topmost layers, was the dominant factor influencing the GaInAs layer’s quality. These results allow an understanding of the contributions of each characterization technique in the analysis of multi-junction solar cells.

Degradation study on triple junction inverted metamorphic InGaP/InGaAs-GaAsP MQW/InGaAs multiple quantum well solar cell using advanced physical models

In this work, we investigated triple-junction (3J) solar cell with inverted metamorphic structure, used for space application. Unlike conventional inverted metamorphic (IMM) InGaP/GaAs/In0.30Ga0.70As, we propose inclusion of MQW in the middle GaAs for better spectral response and radiation resistance. Using Crosslight APSYS, the important non-idealities such as surface recombination velocity (SRV) and threading dislocation density (TDD) are defined and its effect on device characteristics are presented. For TDD upto 1 × 105 cm−2 in the graded buffer InGaP and the bottom In0.30Ga0.70As subcell, the influence on device characteristics has obtained to be very marginal. Under 1-sun AM0 spectrum, the proposed triple junction InGaP/InGaAs-GaAsP MQW/InGaAs inverted metamorphic solar cell (3J MQW IMM) attained a maximum efficiency of 37.15% (without SRV) and 36.39% (at 104 cm/s SRV).

Forecasting solar-to-hydrogen and solar-to-methane energy conversion efficiency using Si and IMM PV-modules: A case-study in Japan

The solar-to-gas (StG) conversion system is a potential pathway for accelerating zero-carbon energy sources. In our previous study, outdoor StG conversion was accomplished using triple-junction concentrator photovoltaic (CPV) modules. The system achieved the highest performance with sets of DC/DC converters and electrochemical (EC) cells. Therefore, we aimed to investigate the prospective StG conversion from PV systems if such a system is installed in Japan. A power generation prediction model considering all weather conditions, called the Miyazaki Spectrum to Energy (MS2E), has been developed using the METPV-11 meteorological database at the University of Miyazaki. Accordingly, the amount of energy generated by various PV systems could be forecasted nationwide from the global irradiance data. In this study, we applied the MS2E PV energy prediction method and approached the potential StG conversion efficiency of silicon (Si) PV and inverted metamorphic (IMM) PV systems across Japan. Based on the actual StG measurement data, we approximated the conversion of each subsystem. The simulation results show that IMM modules can provide higher StG conversion than Si modules.

Effects of Zn diffusion in tunnel junction and its solution for high efficiency large area flexible GaInP/GaAs/InGaAs tandem solar cell

The zinc (Zn) diffusion effects on metal–organic chemical vapor deposition grown flexible inverted metamorphic (IMM) GaInP/GaAs/InGaAs triple junction solar cell performance have been investigated. By studying electrical and spectral properties of solar cells with different configuration, it was found out that the Zn diffusion from GaAs middle cell AlGaAs:Zn back surface field (BSF) layer into AlGaAs/GaAs tunnel junction is the main reason for I–V curve inflection and low fill factor. Besides, the thermal annealing effects caused by the long epitaxial growth time also has significant effect on Zn diffusion and degrades the overall cell performance. These adverse effects caused by Zn diffusion was suppressed by replacing Zn with carbon as the p-type dopant source in BSF layer, and the thermal annealing effects was solved by fine tuning InGaAs bottom subcell base layer thickness. A large area, 4 × 2 cm2, flexible IMM GaInP/GaAs/InGaAs triple junction solar cell with 34.52% efficiency under AM 1.5D solar spectrum has been successfully fabricated.

1 MeV electron and 10 MeV proton irradiation effects on inverted metamorphic GaInP/GaAs/InGaAs triple junction solar cell

The degradation characteristic of GaInP/GaAs/In0.3Ga0.7As inverted metamorphic (IMM) triple junction solar cells irradiated by 1 MeV electron and 10 MeV proton have been studied and compared to that of traditional GaInP/InGaAs/Ge lattice matched (LM) triple junction solar cells. Both IMM and LM solar cells exhibited very good radiation resistance upon 3.16 × 1010 MeV/g displacement damage dose electron and proton irradiation level. The remaining factor of maximum output power is 0.86 and 0.85 for electron irradiation and 0.73 and 0.75 for proton irradiation in IMM and LM solar cells, respectively. IMM solar cell showed better properties in current matching in end-of-life condition comparing to that of LM solar cells. 1 MeV electron to 10 MeV proton irradiation relative damage coefficients, Rep, for IMM and LM solar cells are determined as 3.11 and 2.78, respectively, by using equivalent displacement damage dose model. The radiation damage coefficient of diffusion length upon 1 MeV electron and 10 MeV proton irradiation for both types of solar cell structures have been calculated.

Study of degradation in 3J inverted metamorphic (IMM) solar cell due to irradiation-induced deep level traps and threading dislocations using finite element analysis

Abstract This paper emphasizes on III-V material based inverted metamorphic triple junction (3J IMM) solar cell as an alter-native to 3J lattice-matched InGaP/GaAs/Ge design (3J LM). 1-sun AM0 efficiency is obtained to be 7% higher for the proposed 3J IMM InGaP/GaAs/In0.30Ga0.70As design compared to the experimental 3J LM solar cell. The mi- nority carrier lifetime as a function of threading dislocation density (TDD) is presented for p-In0.30Ga0.70As material. The influence of TDD in the buffer and the bottom In0.30Ga0.70As subcell on the device characteristics is presented and analyzed. In addition to TDD, the degradation of solar cell output parameters is plotted as a function of trap concentration by considering irradiation-induced deep level traps. We compared the degradation tendencies of short circuit current density Jsc, open circuit voltage Voc, and efficiency of 3J IMM and 3J LM solar cells with respect to trap concentration. This analysis became possible by defining trap related parameters and the corresponding carrier lifetime changes using the crosslight APSYS tool. In addition to superior radiation resistance, the proposed device has shown 4% higher efficiency compared to 3J LM device even with the inclusion of non-idealities such as surface recombination velocity, TDD, and trap concentration.

Flexible four-junction inverted metamorphic AlGaInP/AlGaAs/ In0.17Ga0.83As/In0.47Ga0.53As solar cell

A flexible four-junction (4 J) AlGaInP/AlGaAs/In0.17Ga0.83As/In0.47Ga0.53As solar cell with the band gap energy of 1.92/1.53/1.18/0.82eV was fabricated. Taking advantages of aluminum (Al)-contained material as well as metamorphic growth, the design of multiple junction solar cells became much easier and more flexible. In order to accommodate lattice mismatch between two InGaAs sub cells, compositionally step-graded AlGaInAs buffer layers were applied to release the mismatch strain during the inverted metamorphic (IMM) 4 J solar cells growth. A flexible 4 J solar cell on a 50 μm thick polyimide (PI) film was successfully fabricated by using temporary bonding and epitaxial layer lift-off via selective wet chemical etching. A conversion efficiency of 25.76% (AM1.5G) with an open circuit voltage of 3.46V, a short-circuit current density of 9.07 mA/cm2 and a fill factor of 82.14% was obtained without anti-reflection coating (ARC), and it would be higher than 32% by ARC integration. The mass density of the 4 J flexible solar cell was only 467 g/m2, and the specific power was up to 550 W/kg.

High efficiency thin film GaInP/GaAs/InGaAs inverted metamorphic (IMM) solar cells based on electroplating process

Highly efficient, lightweight, and flexible III-V compound multi-junction solar cells play an important role in the wearable electronic field. GaInP/GaAs/InGaAs inverted metamorphic (IMM) solar cells directly grown on an N-doped GaAs substrate by a GaInP etch stop layer were fabricated. The AlGaInAs graded buffer layer is grown to relax the strain of InGaAs with GaAs. Most misfit dislocations are localized at the internal interfaces of the graded buffer and do not appear to propagate. Then, the solar cells are fabricated by the copper-plated process, and Cu thin films serve as not only the flexible support but also the P-type electrode. The device had a total thickness of less than 35 μm, a mass density of less than 0.03 g/cm2, and can exhibit excellent bendability. Under the AM1.5G solar illumination, the thin film solar cell has the best photovoltaic conversion efficiency of 33.13% with the Voc of 2.86 V, a Jsc value of 13.55 mA/cm2, and a FF of 85.49%. This method can be used to prepare flexible thin film solar cells simply and efficiently.

Epitaxial Lift-off (ELO) of InGaP/GaAs/InGaAs solar cells with quantum dots in GaAs middle sub-cell

We report the first demonstration of MOVPE-grown inverted metamorphic (IMM) cells with QDs embedded in the middle GaAs sub-cell. The IMM cells were fabricated on full 4″ wafer using Epitaxial Lift off (ELO) technology. GaAs sub-cell embedded with 10 and 20 periods of InAs/GaP strain compensated QDs showed increase in current with number of QD periods. The single junction GaAs sub cell embedded with 20 periods of InAs/GaP strain compensated QDs showed 3.2% relative increase in JSC in comparison with control sample without QDs. Integrated short circuit (JSC) from measurements of external quantum efficiency (EQE) of currents showed a 65% increase in sub-band collection in the GaAs sub-cell when the number of QD layers increased from 10 to 20. IMM cells with QD's embedded in the middle cell showed minimal loss in open circuit voltage (VOC) in comparison to control sample without QDs. An efficiency of 30% under 1-sun AM0 spectrum was obtained for IMM cells with 10 xs of InAs/GaP QDs in GaAs sub-cell. Quantum efficiency remaining factor of > 95% in the QD absorption region (940 nm) was measured for IMM devices with InAs/GaAs QD enhanced GaAs sub-cells irradiated with 1 MeV electrons under 2E15 /cm2 fluence.

Direct Comparison of Ground and In-Flight Measurements of New Multi-Junction Solar Cell Technologies

The pace of development for new photovoltaic structures such as the inverted meta-morphic (IMM) IIIV cells, exceeds the pace at which spectrally matched, calibrated, solar cells can be created due to the infrequent opportunities of balloon or space based calibration. As such, laboratories must rely on previous generation AM0 calibrated cells and make appropriate corrections. Equally challenging is measuring the same cells in space without a controlled laboratory environment. It is within this context, the 3rd Forward Technology Solar Cell Experiment (FTSCE III), measured three, four and five junction advanced technology solar cells in space. This report compares the beginning-of-life in-flight measurements with the laboratory measurements made before flight.

Design Flexibility of Ultrahigh Efficiency Four-Junction Inverted Metamorphic Solar Cells

The inverted metamorphic solar cell has highly tunable bandgaps, in part due to the metamorphic subcells. Using phosphide-based compositionally graded buffers, we show a wide variety of GaInAs solar cells, ranging in bandgap from 1.2 to 0.7 eV. These metamorphic subcells are all high quality and can be used for a wide variety of multijunction designs. GaInAs solar cells with 0.70 eV bandgaps are developed using an InAsP buffer that extends beyond the InP lattice constant, allowing access to an additional 2 mA/cm2 of photocurrent at AM1.5D and 25 °C. This subcell is implemented into a four-junction inverted metamorphic solar cell combined with an appropriate antireflective coating, which increases the series-connected multijunction current by 0.5 mA/cm2 with respect to designs using 0.74-eV GaInAs. However, the optimal design depends on the spectrum and operating temperature. We show how the device flexibility can be used to fine-tune the design for various spectra in order to maximize energy yield for a given operating condition. One-sun devices achieve 35.3 ± 1.2% efficiency under the AM0 spectra and 37.8 ± 1.2% efficiency under the global spectra at 25 °C. Concentrator devices designed for elevated operating temperature achieve 45.6 ± 2.3% peak efficiency under 690× the direct spectrum and 45.2 ± 2.3% efficiency at 1000× and 25 °C. Device optimization is performed for the direct spectrum on 1-sun devices with 2% shadowing, which achieve 39.8 ± 1.2% efficiency under the direct spectrum at 1 sun, highlighting the excellent performance and bandgap tunability of the four-junction inverted metamorphic solar cell.

Investigation of inverted metamorphic GaInP/GaAs/In0.3Ga0.7As (1 eV) triple junction solar cells for space applications

High efficiency inverted metamorphic (IMM) GaInP/GaAs/In0.3Ga0.7As(1.0 eV) triple-junction solar cells have been fabricated by growing In0.3Ga0.7As(1.0 eV) sub-cell using step-graded buffer layer, which is 2% lattice mismatch to the GaAs middle cell. The high crystalline quality and low threading dislocation density are confirmed by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). The quantum efficiency and I-V characteristic are measured for the IMM GaInP/GaAs/In0.3Ga0.7As solar cells, as well as for the conventional triple-junction solar cell based on Ge substrate (GaInP/GaAs/Ge). The efficiency of the designed cell with an area of 10.922 cm2 is 32.64% (AM0, 25 ℃), which is 3% higher than the conventional GaInP/GaAs/Ge triple junction solar cell.

Enhanced Omnidirectional Photovoltaic Performance of Solar Cells Using Multiple‐Discrete‐Layer Tailored‐ and Low‐Refractive Index Anti‐Reflection Coatings

AbstractAn optimized four‐layer tailored‐ and low‐refractive index anti‐reflection (AR) coating on an inverted metamorphic (IMM) triple‐junction solar cell device is demonstrated. Due to an excellent refractive index matching with the ambient air by using tailored‐ and low‐refractive index nanoporous SiO2 layers and owing to a multiple‐discrete‐layer design of the AR coating optimized by a genetic algorithm, such a four‐layer AR coating shows excellent broadband and omnidirectional AR characteristics and significantly enhances the omnidirectional photovoltaic performance of IMM solar cell devices. Comparing the photovoltaic performance of an IMM solar cell device with the four‐layer AR coating and an IMM solar cell with the conventional SiO2/TiO2 double layer AR coating, the four‐layer AR coating achieves an angle‐of‐incidence (AOI) averaged short‐circuit current density, JSC, enhancement of 34.4%, whereas the conventional double layer AR coating only achieves an AOI‐averaged JSC enhancement of 25.3%. The measured reflectance reduction and omnidirectional photovoltaic performance enhancement of the four‐layer AR coating are to our knowledge, the largest ever reported in the literature of solar cell devices.

The origin of Himalayan anatexis and inverted metamorphism: Models and constraints

The key to comprehending the tectonic evolution of the Himalaya is to understand the relationships between large-scale faulting, anatexis, and inverted metamorphism. The great number and variety of mechanisms that have been proposed to explain some or all of these features reflects the fact that fundamental constraints on such models have been slow in coming. Recent developments, most notably in geophysical imaging and geochronology, have been key to coalescing the results of varied Himalayan investigations into constraints with which to test proposed evolutionary models. These models fall into four general types: (1) the inverted metamorphic sequences within the footwall of the Himalayan thrust and adjacent hanging wall anatexis are spatially and temporally related by thrusting; (2) thrusting results from anatexis; (3) anatexis results from normal faulting; and (4) apparent inverted metamorphism in the footwall of the Himalayan thrust is produced by underplating of right-way-up metamorphic sequences. We review a number of models and find that many are inconsistent with available constraints, most notably the recognition that the exposed crustal melts and inverted metamorphic sequences not temporally related. The generalization that appears to best explain the observed distribution of crustal melts and inverted metamorphic sequences is that, due to specific petrological and tectonic controls, episodic magmatism and out-of-sequence thrusting developed during continuous convergence juxtaposing allochthonous igneous and metamorphic rocks. This coincidental juxtaposition has proven to be something of a red herring, unduly influencing attention toward finding a causal relationship between anatexis and inverted metamorphism.

Flow controlled inverted metamorphism in shear zones

Numerous processes and models have been developed in order to explain inverted metamorphism in shear zones. This article demonstrates, by means of continuum mechanics, that the orientation of a sample profile across a shear zone before and after deformation can be used to quantify the conditions under which inverted metamorphism is likely to have developed. A thrusting shear zone deforming under ideal simple shear will develop an inverted metamorphic zonation if the angle between the thrust and isotherms is greater than 5–10°, even at only moderate strains. If the flow is general shear, this angle is considerably larger (i.e. >60° for a kinematic vorticity number of W k=0.5). Additionally, the stretch of the sample profile across the shear zone, which is not influenced by the flow type, bears important implications for the interpretation of petrological, geochronological and structural data. Although this kinematic model is clearly an end-member model, neglecting dissipative processes, it can easily account for the structural and petrological data of the inverted metamorphism observed throughout the Higher Himalayan Crystalline wedge in the Sutlej Valley (India).

Deformation-induced inverted metamorphic field gradients: an example from the southeastern Canadian Cordillera

Exhumed middle crustal rocks of the hinterland of the southeastern Canadian Cordillera were deformed and metamorphosed during Mesozoic and Tertiary progressive crustal thickening. High structural levels were transported to the northeast relative to lower levels through a combination of thrusting and ductile non-coaxial flow. Progressive growth of the orogen and advance of hinterland rocks toward the foreland are revealed through analysis of diachronous metamorphism and associated deformation. At the deepest exposed level, allochthonous rocks of the orogen (Selkirk allochthon) structurally overlie Early Proterozoic basement and younger cover rocks (Monashee complex) that are correlated with autochthonous North American crust underlying the eastern Foreland Belt. The crustal zone, which marks the boundary between the Selkirk allochthon and Monashee complex, exhibits an inverted metamorphic field gradient. New data presented in this paper refute previous interpretations, which asserted that the metamorphic inversion is a result of the downward transfer of heat from the allochthon to the underlying Monashee complex. Rather, the inversion is attributed to synmetamorphic non-coaxial progressive deformation. A model is proposed in which substantial northeastward directed shear strain and attendant attenuation led to lateral transfer of rocks thereby preserving evidence of strongly diachronous deformation and an apparent inverted metamorphism.

A Late Miocene-Pliocene origin for the Central Himalayan inverted metamorphism

Perhaps the best known occurrence of an inverted metamorphic sequence is that found immediately beneath the Himalayan Main Central Thrust (MCT), generally thought to have been active during the Early Miocene. However, in situ 208Pb/232Th dating of monazite inclusions in garnet indicates that peak metamorphic recrystallization of the MCT footwall occurred in this portion of the central Himalaya at only ca. 6 Ma. The apparent inverted metamorphism appears to have resulted from activation of a broad shear zone beneath the MCT which tectonically telescoped the young metamorphic sequence. This explanation may resolve some outstanding problems in Himalayan tectonics, such why the MCT and not the more recently initiated thrusts marks the break in slope of the present day mountain range. It also renders unnecessary the need for exceptional physical conditions (e.g., high shear stress) to explain the generation of the Himalayan leucogranites.

Deformation and metamorphism within the Main Central Thrust zone, Arun Tectonic Window, eastern Nepal

Abstract The Lesser Himalayan Arun Tectonic Window comprises the Upper Precambrian, polymetamorphosed metasediments of the Nawakot Complex. These are tectonically overlain by Precambrian gneisses of the Higher Himalayan Kathmandu Complex. The main phase metamorphism within the Higher Himalayan rocks predated thrusting along the Main Central Thrust. By contrast, the main metamorphism (M2) within the Nawakot Complex commenced synchronously with it being underthrust during D2 along the Main Central Thrust Zone beneath the amphibolite facies rocks of the Kathmandu Complex. During D2 rocks on both sides of the Main Central Thrust Zone underwent intensive mylonitization within a several hundred meter wide zone of non-coaxial shearing. Although the stratigraphic order within the Nawakot Complex is the right way up, rocks within the Arun Tectonic Window show a concentric inverted metamorphic zoning, ranging from lower greenschist facies in the core of the window, up to lower amphibolite facies at the outer edge of the window. This ‘inverted metamorphism’ (M2) of the Nawakot Complex originated as a result of syn- to post-D2 downward heat conduction from the ‘hot’ hanging wall of the Main Central Thrust onto the ‘cold’ footwall. This heat flow also caused the strong retrograde overprinting at the base of the Kathmandu Complex. After a static period, a late- to post-M2 NNE-shortening (D3) commenced along the Main Boundary Thrust. The Arun Tectonic Window is the result of doming of the Main Central Thrust during D4 followed by erosional exhumation.

Inverted metamorphic zonation and large-scale thrusting in the Variscan Belt: an example in the French Massif Central

Summary Half of the northern part of the French Massif Central has been shown to be allochthonous. In the allochthonous rocks, preserved high-pressure granulites represent an early tectonometamorphic event which took place before thrusting. During the southward-directed overthrusting of this high-grade metamorphic slab a plurifacial inverted metamorphism was developed in the underlying sediments. Adjacent areas show different types of metamorphism in the autochthonous and parautochthonous pelites. The climax of the metamorphism is shown to have been reached by the end of the thrusting episode. This was followed by the retrogression of the high-grade rocks and the establishment of a low-pressure metamorphism in both the thrust unit and the autochthonous-parautochthonous terranes beneath. We describe this example of inverted metamorphic zonation associated with the large-scale thrusting of an already metamorphosed series.