Stabilising Perovskite Solar Cells with Earth-Abundant Chalcogenide Nanoparticles

The commercialisation of perovskite photovoltaic (PV) technologies requires advancements in large-area module efficiency, scalable and cost-effective manufacturing, and long-term operational stability. Stability issues in perovskite solar cells (PSCs) often stem from the materials used in the hole-transporting layer (HTL). Innovative, sustainable, and affordable hole-transport materials (HTMs) are crucial to address these challenges. Cu₂ZnSnS₄ (CZTS), an earth-abundant p-type semiconductor traditionally used as a light-absorbing material in heterojunction solar cells, has recently gained attention as an HTL for PSCs due to its desirable electronic properties. This study explores the synthesis and application of CZTS nanoparticles (NPs) as an HTM in PSCs. The nanoparticles were produced using a hot-injection method under an oxygen-free environment and subsequently processed into an ink formulation for spin-coating. The resulting CZTS thin films, approximately 50 nm thick, were annealed to ensure structural and optical transparency in the visible solar spectrum. Comprehensive material characterisation—including transmittance, Raman spectroscopy, UV-Vis spectroscopy, scanning electron microscopy, and X-ray diffraction—confirmed the quality and stability of the CZTS layers. Preliminary findings indicate that PSCs employing CZTS as an HTL demonstrate superior stability compared to conventional organic HTM devices. Over one month, the CZTS-based devices retained or even improved their photovoltaic efficiency, unlike organic HTL-based devices, which experienced significant degradation. Current-voltage measurements, external quantum efficiency and photoluminescence spectroscopy analyses revealed enhanced charge injection in the CZTS HTL. These results suggest that CZTS is a robust and sustainable alternative to traditional HTMs, paving the way for more durable perovskite PV technologies.