Highly efficient single junction GaAs thin film solar cell on flexible substrate
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 mm 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.
Scientific reports