2023-07-19 米国国立再生可能エネルギー研究所(NREL)
◆アコースティック・スパリングは従来の剥離層を使った方法よりも素早く、基板から太陽電池を取り外すことができ、再利用によるコスト削減が期待されます。これにより、地球上での応用がより現実的になり、高効率で手頃な価格の太陽電池の実現に向けた一歩となります。さらなる研究により、アコースティック・スパリングで取り外した基板の再利用回数などを評価し、効果的な再利用の実現を目指す計画です。
＜関連情報＞
- https://www.mercomindia.com/nrels-research-reveals-make-cheaper-solar-cells
- https://www.sciencedirect.com/science/article/abs/pii/S2542435123002167
音響的にスポーリングされたGaAs基板上に成長したGaAs太陽電池、27％の効率 GaAs solar cells grown on acoustically spalled GaAs substrates with 27% efficiency
Kevin L. Schulte Steve W. Johnston, Anna K. Braun, Jacob T. Boyer, Anica N. Neumann, William E. McMahon, Michelle Young, Pablo Guimerá Coll, Mariana I. Bertoni, Emily L. Warren, Myles A. Steiner
Joule Published: June 19, 2023
DOI:https://doi.org/10.1016/j.joule.2023.05.019
Context & scale
III–V solar cells offer the highest solar photovoltaic conversion efficiencies of any technology, but high manufacturing costs limit their use in terrestrial applications. Roughly one-third of the cost of a III–V solar cell comes from the single-crystalline substrate on which it is grown. Acoustic spalling is a new process that enables the rapid cleavage of III–V devices from their parent substrates, potentially enabling substrate reuse if high-efficiency devices can be grown on previously spalled substrates.
In this work, we study the vapor growth of GaAs solar cells on previously spalled GaAs substrates and develop an understanding of how the spalled surface affects subsequent device growth and performance. We develop a GaAs device grown on a previously spalled substrate with 27% efficiency, which compares favorably to GaAs efficiencies obtained on any III–V substrate. These results highlight the potential of acoustic spalling as a viable substrate reuse technology.
Summary
Acoustic spalling presents a potentially low-cost reuse pathway for III–V epitaxial growth substrates via exfoliation of device layers with recovery and reuse of the substrate. However, surface features formed during spalling can reduce the performance of subsequently grown devices. We develop an understanding of how the surface morphology of acoustically spalled substrates affects GaAs solar cell performance and develop strategies to mitigate these impacts. We demonstrate that minor planarization of the surface by wet chemical etching and/or epitaxial growth, or the redesign of the device structure to thicken critical layers, prevents performance degradation. Using these strategies, we demonstrate a 0.25 cm2 single-junction GaAs device with 26.9% ± 0.2% photovoltaic conversion efficiency under the AM1.5G spectrum grown on an acoustically spalled substrate. These results enable the growth of high-performance III–V devices on non-traditional substrates with the potential for significantly reduced device costs.
