Search

• TiN-Al 2 O 3 -Cr gradient layer is introduced to tailor residual stress of CZTSSe. • 60 nm sputtered gradient layer contributes the best heterojunction characteristic. • Gradient layer introduced device exhibits more satisfying bending stability. In an effort to promote the mechanical endurance of flexible Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells, a convenient and effective strategy for introducing a TiN-Al 2 O 3 -Cr gradient layer is proposed, which can effectively tailor the residual stress and improve the heterojunction characteristic of solar cell. Benefitted from the optimum TiN-Al 2 O 3 -Cr gradient layer with 60 nm, CZTSSe presents a released residual stress of −3.33 GPa and an optimized heterojunction characteristic with the CBO of −0.28 eV. Furthermore, the PCE of flexible device is remarkably improved from 3.31 % to 5.01 %, which can maintain 85 % of the original efficiency after harsh bending. The proposed gradient layer strategy may pave a thriving way for congener flexible and portable cells. [ABSTRACT FROM AUTHOR]