Abstract
There has been much interest in developing a thin-film solar cell because it is lightweight and flexible. The GaAs thin-film solar cell is a top contender in the thin-film solar cell market in that it has a high power conversion efficiency (PCE) compared to that of other thin-film solar cells. There are two common structures for the GaAs solar cell: n (emitter)-on-p (base) and p-on-n. The former performs better due to its high collection efficiency because the electron diffusion length of the p-type base region is much longer than the hole diffusion length of the n-type base region. However, it has been limited to fabricate highly efficient n-on-p single-junction GaAs thin film solar cell on a flexible substrate due to technical obstacles. We investigated a simple and fast epitaxial lift-off (ELO) method that uses a stress originating from a Cr/Au bilayer on a 125-μm-thick flexible substrate. A metal combination of AuBe/Pt/Au is employed as a new p-type ohmic contact with which an n-on-p single-junction GaAs thin-film solar cell on flexible substrate was successfully fabricated. The PCE of the fabricated single-junction GaAs thin-film solar cells reached 22.08% under air mass 1.5 global illumination.
Highlights
In the last few decades, much effort has gone into developing a thin-film solar cell to take advantage of its light weight and flexibility
We have demonstrated a highly efficient GaAs thin-film solar cell fabricated on a flexible substrate using a simple and fast epitaxial lift-off (ELO) method that utilizes the stress of a sputtered Cr/Au bilayer
The cutoff seen below about 470 nm is generally explained by the inefficient extraction of carriers generated near the window and emitter layers
Summary
In the last few decades, much effort has gone into developing a thin-film solar cell to take advantage of its light weight and flexibility. Manufacturing costs are significantly reduced by reusing the GaAs substrate[4,5,6] Because of these advantages, the ELO method for fabricating GaAs thin-film solar cells has been widely investigated. Because of a lack of an HF-resistant p-contact metal this simple ELO method could be applied only to the p (emitter)-on-n (base) solar cell structure, where the Be-doped p-GaAs layer has to be grown prior to the n-GaAs layer using molecular beam epitaxy (MBE). We have demonstrated a highly efficient GaAs thin-film solar cell fabricated on a flexible substrate using a simple and fast ELO method that utilizes the stress of a sputtered Cr/Au bilayer. In order to realize the highly efficient and flexible thin film solar cell, an HF-resistant AuBe/Pt/Au metal combination is employed as a new p-type ohmic contact, by which an n (emitter)-on-p (base) single-junction GaAs thin-film www.nature.com/scientificreports/. The single-junction GaAs thin-film solar cell on a flexible substrate is made using the standard solar cell fabrication process
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