TAGRA 2025

Copper Iodide (CuI) thin films synthesized using monoethanolamine (MEA) as a green solvent exhibit high optical transparency and uniform planar morphology, supporting their function as efficient hole transport layers (HTLs) in perovskite solar cells. Using this low-temperature, additive-free method, γ-CuI with a zinc-blende structure was successfully obtained. Despite these promising outcomes, maintaining uniform structural integrity and electrical stability during low-temperature processing remains a key challenge, especially when targeting mechanically flexible perovskite devices. The CuI films were deposited on Indium-doped Tin Oxide (ITO) substrates via solution-processable spin coating and subsequently annealed at temperatures between 60 °C and 120 °C. SEM and XRD analyses indicate that annealing temperature critically governs grain evolution, preferred crystallographic orientation, and structural parameters such as crystallite size, lattice constant, lattice strain, and dislocation density. The film annealed at 80 °C displayed a sharp nanoflower-like morphology with favourable conductivity and a stable band gap. These observations confirm that precise annealing optimization is essential for producing structurally robust CuI thin films suitable for high-performing PSC applications.