Antimony-Decorated Reduced Graphene Oxide in Zinc Oxide Buffer Layer for Thin-Film Solar Cells

Recently, nanoparticle–graphene oxide composites have emerged as promising materials for optoelectronic applications. In this study, a graphene oxide (GO) composite anchored with Sb nanoparticles (Sb NPs) was synthesized via a microwave-assisted method. Comprehensive characterization was conducted to compare the structural, optical, thermal, and electrochemical properties of Sb-rGO with those of pristine GO and Sb NPs. Subsequently, GO, Sb NPs, and Sb-rGO were incorporated into a ZnO electron transport layer (ETL) in Cu 2 ZnSnS 4 (CZTS) kesterite solar cells. Incorporation of Sb-rGO yielded a power conversion efficiency (PCE) of 4.24%, surpassing the efficiencies achieved with GO (3.85%) and Sb NPs (3.94%), primarily due to enhanced electron extraction from the absorber. Electrochemical impedance spectroscopy and dark current–voltage analysis confirmed that the performance enhancement arises from reduced charge-carrier recombination and improved charge collection. The ZnO:GO, ZnO:Sb NPs, and ZnO:Sb-rGO layers exhibited optical transmittance above 85%, and the corresponding devices retained more than 79% of their initial PCE after 20 days of storage. These results show the beneficial role of Sb-rGO in improving both the efficiency and stability of CZTS-based kesterite solar cells.