Fundamental Issues in Manufacturing Photovoltaic Modules Beyond the Current Generation of Materials

Many methods to improve the solar cell’s efficiency beyond current generation of bulk and thin film of photovoltaic (PV) devices have been reported during the last five decades. Concepts such as multiple exciton generations (MEG), carrier multiplication (CM), hot carrier extraction, and intermediate band solar cells have fundamental flaws, and there is no experimental evidence of fabricating practical higher efficiency solar cells based on the proposed concepts. To take advantages of quantum features of nanostructures for higher performance PV devices, self-assembly-based bottom-up processing techniques are not suitable for manufacturing due to inherent problems of variability, defects, reliability, and yield. For processing nanostructures, new techniques need to be invented with the features of critical dimensional control, structural homogeneity, and lower cost of ownership as compared to the processing tools used in current generations of bulk and thin-film solar cells.

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Temperature Dependence of Carrier Extraction Processes in GaSb/AlGaAs Quantum Nanostructure Intermediate-Band Solar Cells

Nanomaterials ◽

10.3390/nano11020344 ◽

2021 ◽

Vol 11 (2) ◽

pp. 344

Author(s):

Yasushi Shoji ◽

Ryo Tamaki ◽

Yoshitaka Okada

Keyword(s):

Solar Cells ◽

Molecular Beam ◽

Optical Excitation ◽

Material System ◽

Intermediate Band ◽

Temperature Characteristics ◽

Quantum Nanostructures ◽

Band Engineering ◽

Intermediate Band Solar Cells ◽

Carrier Extraction

From the viewpoint of band engineering, the use of GaSb quantum nanostructures is expected to lead to highly efficient intermediate-band solar cells (IBSCs). In IBSCs, current generation via two-step optical excitations through the intermediate band is the key to the operating principle. This mechanism requires the formation of a strong quantum confinement structure. Therefore, we focused on the material system with GaSb quantum nanostructures embedded in AlGaAs layers. However, studies involving crystal growth of GaSb quantum nanostructures on AlGaAs layers have rarely been reported. In our work, we fabricated GaSb quantum dots (QDs) and quantum rings (QRs) on AlGaAs layers via molecular-beam epitaxy. Using the Stranski–Krastanov growth mode, we demonstrated that lens-shaped GaSb QDs can be fabricated on AlGaAs layers. In addition, atomic force microscopy measurements revealed that GaSb QDs could be changed to QRs under irradiation with an As molecular beam even when they were deposited onto AlGaAs layers. We also investigated the suitability of GaSb/AlGaAs QDSCs and QRSCs for use in IBSCs by evaluating the temperature characteristics of their external quantum efficiency. For the GaSb/AlGaAs material system, the QDSC was found to have slightly better two-step optical excitation temperature characteristics than the QRSC.

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Quantum Dot Solar Cells

Nanotechnology ◽

10.4018/978-1-4666-5125-8.ch016 ◽

2014 ◽

pp. 406-429

Author(s):

Yoshitaka Okada ◽

Katsuhisa Yoshida ◽

Yasushi Shoji

Keyword(s):

Solar Cells ◽

Quantum Dot ◽

High Efficiency ◽

Research Topics ◽

Intermediate Band ◽

Hot Carrier ◽

Quantum Dot Solar Cells ◽

High Efficiency Solar Cells ◽

Hot Carrier Effects ◽

Low Dimensional

Advanced concepts for high efficiency solar cells such as hot carrier effects, Multi-Exciton Generation (MEG), and Intermediate-Band (IB) absorption in low-dimensional nanostructures are under focused research topics in recent years. Among various potential approaches, this chapter is devoted to the device physics and development of the state-of-the-art technologies for quantum dot-based IB solar cells.

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