Low-cost kesterite (CZTS) bilayers as an effective hole-transport layer for perovskite solar cells

This study investigates the utility of Copper Zinc Tin Sulfide (CZTS) thin films as inorganic hole-transporting layers (HTLs) in low-temperature perovskite solar cells (PSCs). The primary goal is to improve power conversion efficiencies (PCE) in PSCs using CZTS thin films fabricated through solution-based methods, with CH3NH3PbI3 perovskite and ZnO serving as the light-absorbing and electron-transporting components, respectively. Precise control over CZTS thin film growth significantly influences the formation of uniform perovskite layers. The study underscores the importance of achieving dense ZnO films with suitable grain sizes to confirm consistent coverage of perovskite films, enabling efficient charge transport while reducing recombination at the CZTS/perovskite interface. Results reveal that CZTS/CZTS bilayers exhibit superior photoelectrochemical performance compared to conventional CZTS(A)/FTO and CZTS(B)/CZTS(A) configurations. Evaluation of water splitting performance demonstrates that the CZTS/CZTS bilayer photoelectrode achieves the maximum photocurrent density, reaching 12 mA/cm2 vs. Ag/AgCl, with an Incident Photon-to-Current Efficiency of 9 % at 400 nm and an applied potential of 0.4V vs. Ag/AgCl. The study comprehensively examines CZTS impact on PSC photovoltaic properties and stability, culminating in a high-performance device with a PCE potential of up to 7 %. This underscores the pivotal role of CZTS− perovskite contacts in determining PSC photovoltaic performance and highlights CZTS potential as a versatile HTM for various PSCs designs.