Vapor-Phase Incorporation of Ge in CZTSe Absorbers for Improved Stability of High-Efficiency Kesterite Solar Cells

We report an approach to incorporate Ge into Cu2ZnSnSe4 using GeSe vapor during the selenization step of alloyed metallic precursors. The incorporation slowly begins at T ≈ 480 °C and peaks 530 °C, resulting in a Ge-based composition shift inside previously formed kesterite layer. initially observe formation Ge-rich surface layer that merges homogeneous distribution incorporated element further dwelling stage annealing. This is very versatile could be used many similar fabrication processes for incorporating CZTSe-absorber layers. Because vapor-based happens after absorber film towards end process, most process parameters precursor structure may not need any significant re-optimization. careful integration this help reduce Sn-related deep defects accompanying VOC losses. best CZTGSe-power-conversion efficiency obtained series 10.4 % (with EG = 1.22 eV, FF 54%, JSC 36 mA/cm2, 540 mV, VOCdef,SQ 417 mV). These results demonstrate potential absorbers.