Abstract
This study examines the effect of ultrathin aluminum oxide (Al(2)O(3)) passivation layer on the performance of the kesterite Cu(2)ZnSnS(4) (CZTS) solar cells. The Al(2)O(3) layer was applied at the back CZTS/Mo interface using atomic layer deposition (ALD). Our findings indicate that the interface passivation with Al(2)O(3) can significantly enhance the adhesion of CZTS to Mo, preventing delamination during annealing. An optimal Al(2)O(3) thickness of 1-2.5 nm yielded a more than 30% increase in efficiency, primarily through enhancements of the open-circuit voltage (V (oc)) and short-circuit current (I (sc)), which resulted from reduced interface recombination and improved charge collection within the CZTS bulk. Furthermore, the Al(2)O(3) layer modified MoS(2) formation at the CZTS/Mo back interface, reducing series resistance (R (s)). Nevertheless, a thicker Al(2)O(3) layer led to a sharp decrease in efficiency due to increased series resistance and hindered the extraction of holes. Our work reveals that precise control of the Al(2)O(3) layer thickness is essential to optimize CZTS solar cell performance by balancing the benefits of passivation with its potential drawbacks.