Recently, Professor Wu's research group published a new research of “Local Cu Component Engineering to Achieve Continuous Carrier Transport for Enhanced Kesterite Solar Cells” in the Journal ACS Applied Materials & Interfaces (ACS Appl. Mater. Inter., 2021, 13, 795−805). (IF=8.758, JCR District 1).)

Article link: https://pubs.acs.org/doi/10.1021/acsami.0c21008.

Although the traditional Cu-poor architecture addresses many limitations for Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells, its further development still encounters in efficiency bottleneck, primarily arising from the inferior charge transport within quasineutral region and enlarged recombination at back contact. On the contrary, the electrical benign kesterite compound with higher Cu content may compensate these shortages, but it will degrade device performance more pronouncedly at front contact duo to the Fermi level pinning and more electric shunts. Based on the electric disparities on their independent side, in this work, we propose a new status of Cu component by exploring a large grain/fine grain/large grain trilayer architecture with higher Cu content near back contact and lower Cu content near front contact. The benefits of this bottom Cu-higher strategy are that it imposes a concentration gradient to drive carrier diffusion towards front contact and decreases the valence band edge offset in the rear of the device to aid in holes extraction. As well, it maintains the Cu-poor architecture at near surface to facilitate hole quasi-Fermi level splitting. In return, the local Cu component engineering mediated electric advances contribute the highest efficiency of 12.54% for kesterite solar cells using amine-thiol solution system so far.

The first author of this paper is Yuechao Zhao and Xiangyun Zhao of Key Laboratory of Special Functional Materials, and the corresponding authors are Professor Sixin Wu and Associate Professor Dongxing Kou. This work is supported by the National Natural Science Foundation of China, the Science and Technology Department of Henan Province, and the Education Department of Henan Province.