Thermally deposited copper(<sc>i</sc>) thiocyanate thin film: an efficient and sustainable approach for the hole transport layer in perovskite solar cells

Solution-processable deposition of copper(i) thiocyanate (CuSCN) thin films have been widely used to form the hole transport layer (HTL) in optoelectronic applications, namely perovskite and organic solar cells. Herein, we report the thermally deposited CuSCN thin film as an efficient, eco-friendly and solvent-free approach for HTL deposition in inverted perovskite solar cells as an alternative to conventional solution-processed methods. The structural, electrochemical, optical, and morphological properties of thermally deposited CuSCN films were characterized. The long-term electrochemical and optical stability of thermally deposited CuSCN films were examined. The effect of thicknesses (20, 30, 40, 60, and 100 nm) and annealing temperatures (RT, 50, 100, 150, and 200 degrees C) of CuSCN films on the photovoltaic performance were investigated. The optimized device configuration ITO/CuSCN/MAPbI(3)/PC61BM/BCP/Ag with a 30 nm thick CuSCN film annealed at 100 degrees C for 10 min exhibited the maximum power conversion efficiency (PCE) of 15.71% with Voc = 1.01 V, Jsc = 20.2 mA cm-2, and FF = 0.77. For reference, perovskite solar cells without a HTL were fabricated simultaneously. Importantly, the thermally deposited CuSCN-based devices showed excellent reproducibility and stability up to 240 h with similar to 89% retention of the initial PCE. This study demonstrates a new methodology for obtaining better CuSCN films using a thermal deposition technique for efficient, sustainable and scalable electronic device applications.