Impact of buffer layer on kesterite solar cells

Abstract

Recently, several groups have demonstrated high efficiency (Eff) kesterite solar cells which are Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSnSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTSe), Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSnS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTS) and Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSn(SSe) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTSSe) solar cells. The highest efficiency has been achieved via the solution-based CZTSSe single cell by IBM. Comprehensive researches in relation to buffer layer technologies, for instance, Cd-free buffer layers (Zn-based or In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ), and hybrid buffer layer (CdS/In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) were conducted by Solar Frontier. Especially, the hybrid buffer layer showed 12.7% on CZTSSe single cell. Solar Frontier also succeeded in fabricating kesterite submodules and demonstrated high performance on them in NEDO project. Eff of 9.2% on CZTS submodule with hybrid buffer layer and 11.4% on CZTSSe submodule with just CdS buffer layer so far. In this work, we applied the hybrid buffer layer to the CZTSSe submodules and achieved the Eff of 11.8%.