High-Efficient Cd-Free Czts Solar Cells Achieved By Nanoscale Atomic Layer Deposited Aluminium Oxide

Kesterite Cu2ZnSnS4 (CZTS) solar cells are considered as the promising alternative candidate for thin film solar cells, but still being hampered by the relative low V-OC Here, we propose a heterojunction modification strategy by applying atomic layer deposited aluminium oxide (Al2O3) as a passivation layer. Through post-treatment of CZTS absorber by nanoscale ALD Al2O3, the effective lifetime of the minority carrier at the heterojunction improved, indicating a better passivation effects from nanoscale alumina. With a significant gain of Voc by 50 mV, we achieved a device efficiency of 9.9 %, the highest efficiency ever reported for Cd-free CZTS solar cells.