Four-Junction Wafer-Bonded Concentrator Solar Cells Dimroth, Frank; Tibbits, Thomas N. D.; Niemeyer, Markus ...
IEEE journal of photovoltaics,
2016-Jan., 2016-1-00, 20160101, Volume:
6, Issue:
1
Journal Article
Peer reviewed
Open access
The highest solar cell conversion efficiencies are achieved with four-junction devices under concentrated sunlight illumination. Different cell architectures are under development, all targeting an ...ideal bandgap combination close to 1.9, 1.4, 1.0, and 0.7 eV. Wafer bonding is used in this work to combine materials with a significant lattice mismatch. Three cell architectures are presented using the same two top junctions of GaInP/GaAs but different infrared absorbers based on Germanium, GaSb, or GaInAs on InP. The modeled efficiency potential at 500 suns is in the range of 49-54% for all three devices, but the highest efficiency is expected for the InP-based cell. An efficiency of 46% at 508 suns was already measured by AIST in Japan for a GaInP/GaAs//GaInAsP/GaInAs solar cell and represents the highest independently confirmed efficiency today. Solar cells on Ge and GaSb are in the development phase at Fraunhofer ISE, and the first demonstration of functional devices is presented in this paper.
Multijunction (MJ) solar cells achieve high efficiencies by effectively utilizing the solar spectrum. Previously, we have developed III‐V MJ solar cells using smart stack technology, a mechanical ...stacking technology that uses a Pd nanoparticle array. In this study, we fabricated an InGaP/AlGaAs//CuxIn1−yGaySe2 three‐junction solar cell by applying modified smart stack technology with a Pd nanoparticle array and adhesive material. Using adhesive material (silicone adhesive), the bonding stability was improved conspicuously. The total efficiency achieved was 27.2% under AM 1.5 G solar spectrum illumination, which is a better performance compared to our previous result (24.2%) for a two‐terminal solar cell. The performance was achieved by optimizing the structure of the upper GaAs‐based cell and by using a CuxIn1−yGaySe2 solar cell with a specialized performance for an MJ configuration. In addition, we assessed the reliability of the InGaP/AlGaAs//CuxIn1−yGaySe2 three‐junction solar cell through a heat cycle test (from −40°C to +85°C; 50 cycles) and were able to confirm that our solar cells show high resistivity under severe conditions. The results demonstrate the potential of III‐V//CuxIn1−yGaySe2 MJ solar cells as next‐generation photovoltaic cells for applications such as vehicle‐integrated photovoltaics; they also demonstrate the effectiveness of modified smart stack technology in fabricating MJ cells.
We fabricated an InGaP/AlGaAs//CuxIn1−yGaySe2 three‐junction solar cell by applying modified smart stack technology with a Pd nanoparticle array and adhesive material. The total efficiency was 27.2% under AM 1.5 G. The performance was achieved by optimizing the structure of the upper GaAs‐based cell and applying a CuxIn1−yGaySe2 solar cell with high performance specialized for a multijunction (MJ) configuration. The results demonstrate the potential of III‐V//CuxIn1−yGaySe2‐based MJ solar cells as next‐generation photovoltaic cells for applications such as vehicle‐integrated photovoltaics.
Multijunction (MJ) solar cells achieve very high efficiencies by effectively utilizing the entire solar spectrum. Previously, we constructed a III‐V//Si MJ solar cell using the smart stack ...technology, a unique mechanical stacking technology with Pd nanoparticle array. In this study, we fabricated an InGaP/AlGaAs//Si three‐junction solar cell with an efficiency of 30.8% under AM 1.5G solar spectrum illumination. This efficiency is considerably higher than our previous result (25.1%). The superior performance was achieved by optimizing the structure of the upper GaAs‐based cell and employing a tunnel oxide passivated contact Si cell. Furthermore, we examined the low solar concentration performance of the device and obtained a maximum efficiency of 32.6% at 5.5 suns. This performance is sufficient for realistic low concentration photovoltaic applications (below 10 suns). In addition, we characterize the reliability of the InGaP/AlGaAs//Si three‐junction solar cell with a damp heat test (85 °C and 85% humidity for 1000 h). It was confirmed that our solar cells have high long‐term stability under severe conditions. The results demonstrate the potential of GaAs//Si MJ solar cells as next‐generation photovoltaic cells and the effectiveness of smart stack technology in fabricating multijunction cells.
We fabricated an InGaP/AlGaAs//Si three‐junction solar cell with anefficiency of 30.8% using ‘smart stack technology’. The superior performancewas achieved by optimizing the structure of the upper GaAs‐based cell and employing a tunnel oxide passivated contact Si cell. Furthermore, we confirmed the low solar concentration performance with a maximum efficiency of 32.6% at 5.5 suns. The results demonstrate the potential of GaAs//Si multijunction solarcells as next‐generation photovoltaic cells and the effectiveness of smartstack technology in fabrication.
Stacking III-V p-n junctions on top of wafer-based silicon solar cells is a promising way to go beyond the silicon single-junction efficiency limit. In this study, triple-junction GaInP/Al x Ga 1-x ...As//Si solar cells were fabricated using surface-activated direct wafer bonding. Metal-organic-vapor-phase-epitaxy-grown GaInP/Al x Ga 1-x As top cells are bonded at low temperature to independently prepared wafer-based silicon cells. n-Si//n-GaAs interfaces were investigated and achieved bulk-like bond strength, high transparency, and conductivity homogeneously over 4-inch wafer area. We used transfer-matrix optical modeling to identify the best design options to reach current-matched two-terminal devices with different mid-cell bandgaps (1.42, 1.47, and 1.52 eV). Solar cells were fabricated accordingly and calibrated under AM1.5g 1-sun conditions. An improved Si back-side passivation process is presented, leading to a current density of 12.4 mA/cm 2 (AM1.5g), measured for a flat Si cell below GaAs. The best 4 cm 2 GaInP/GaAs//Si triple-junction cell reaches 30.2% 1-sun efficiency.
Abstract
Multijunction (MJ) solar cells achieve high efficiencies by effectively utilizing the solar spectrum. Previously, we have developed III‐V MJ solar cells using smart stack technology, a ...mechanical stacking technology that uses a Pd nanoparticle array. In this study, we fabricated an InGaP/AlGaAs//Cu
x
In
1−
y
Ga
y
Se
2
three‐junction solar cell by applying modified smart stack technology with a Pd nanoparticle array and adhesive material. Using adhesive material (silicone adhesive), the bonding stability was improved conspicuously. The total efficiency achieved was 27.2% under AM 1.5 G solar spectrum illumination, which is a better performance compared to our previous result (24.2%) for a two‐terminal solar cell. The performance was achieved by optimizing the structure of the upper GaAs‐based cell and by using a Cu
x
In
1−
y
Ga
y
Se
2
solar cell with a specialized performance for an MJ configuration. In addition, we assessed the reliability of the InGaP/AlGaAs//Cu
x
In
1−
y
Ga
y
Se
2
three‐junction solar cell through a heat cycle test (from −40°C to +85°C; 50 cycles) and were able to confirm that our solar cells show high resistivity under severe conditions. The results demonstrate the potential of III‐V//Cu
x
In
1−
y
Ga
y
Se
2
MJ solar cells as next‐generation photovoltaic cells for applications such as vehicle‐integrated photovoltaics; they also demonstrate the effectiveness of modified smart stack technology in fabricating MJ cells.
Multijunction solar cells (MJSCs) have attracted attention as next-generation solar cells. In particular, GaAs//Si-based MJSCs are highly efficient with low cost and are expected to gain new ...applications, such as on-vehicle integrations. In this article, we examined a highly efficient In 0.49 Ga 0.51 P/Al 0.06 Ga 0.94 As//Si three-junction solar cell. The bottom Si cell has a tunnel oxide passivated contact structure. The key technology used to fabricate this solar cell is a stacking method that uses Pd nanoparticles (Pd-NPs) and metal-assisted chemical etching (MacEtch) for the bonding interface, which is improved from our previous "smart stack" technology. The MacEtch method has a feature of selective etching for Si around a metal body. Pd-NPs selectively invade the Si cell through the surface of the Si oxide layer, thereby improving the bonding resistivity between the GaAs-based cell and Si cell. Further, this technology aids the management of the bonding gap width by controlling the Pd-NP invasion depth. As a result, an efficiency of 27.6% for the aperture area was attained. The proposed technology is useful for the connection of Si-based cells, enhancing the development of GaAs//Si-based tandem solar cells.
The terrestrial photovoltaic market is dominated by single‐junction silicon solar cell technology. However, there is a fundamental efficiency limit at 29.4%. This is overcome by multijunction ...devices. Recently, a GaInP/GaAs//Si wafer‐bonded triple‐junction two‐terminal device is presented with a 33.3% (AM1.5g) efficiency. Herein, it is analyzed how this device is improved to reach a conversion efficiency of 34.1%. By improving the current matching, an efficiency of 35% (two terminals, AM1.5g) is expected.
The terrestrial photovoltaic market is dominated by single‐junction silicon solar cell technology. However, there is a fundamental efficiency limit at 29.4%. This is overcome by multijunction devices. Recently, a GaInP/GaAs//Si wafer‐bonded triple‐junction two‐terminal device is presented with a 33.3% (AM1.5g) efficiency. Herein, it is analyzed how this device is improved to reach a conversion efficiency of 34.1%.
Multijunction solar cells with four junctions are expected to be the next-generation technology for both space and concentrator photovoltaic applications. Most commercial triplejunction solar cells ...are today grown on germanium, which also forms the bottom subcell. Extending this concept to four junctions with an additional ~1-eV subcell was proven to be challenging. We investigate a new cell concept, which uses direct wafer bonding to combine a metamorphic GaInAs/Ge bottom tandem solar cell with a GaInP/AlGaAs top tandem on GaAs resulting in a monolithic four-junction cell on germanium. This article summarizes results of the cell developments, which have been resulting in a four-junction concentrator cell with 42% efficiency. We implemented a new passivated Ge backside technology to enhance the current generation in the Ge junction, and we propose realistic steps to realize solar cells with 45% efficiency using this cell architecture.
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