Low-Temperature Aqueous Ammonia-Processed Copper (I) Selenocyanate Hole-Transporting Material for Efficient Inverted Perovskite Solar Cells

Abstract

Significant efforts have been reported on copper(I) thiocyanate (CuSCN) as an efficient hole-transporting layer (HTL) for perovskite solar cells. Surprisingly, its higher chalcogen analogue copper (I) selenocyanate (CuSeCN) is unexplored yet, even though CuSeCN has been shown to have different properties compared to CuSCN because of its different electronegativity, polarizability, and size (Se vs S atoms). In this work, we report the synthesis of CuSeCN as an HTL in perovskite solar cells via low-temperature solution-processable deposition from an aqueous ammonia solution. The transparency and thermal stability of CuSeCN films were examined by the deposition of thin films from an aqueous ammonia solution under ambient conditions. The structural, electrical, optical, and morphological properties of the CuSeCN films were characterized by X-ray diffraction, XPS, FTIR, cyclic voltammetry, UV–vis–NIR spectroscopy, and field emission scanning electron microscopy. A single-step fast deposition–crystallization method was used to fabricate low-temperature CuSeCN-based inverted planar perovskite solar cells, with device architecture indium tin oxide (ITO)/CuSeCN/CH3NH3PbI3/PC61BM/BCP/Ag. Furthermore, to examine the effect of the thickness of the HTL on device performance, three different concentrations of CuSeCN solution were used for thin-film deposition in perovskite solar cells. The annealing temperature of the HTL films was optimized to obtain the highest possible device performance. A maximum power conversion efficiency (PCE) of 13.59% (Voc = 0.99 V, Jsc = 18.8 mA/cm2, and FF = 0.73) was achieved with 7.5 mg mL–1 of CuSeCN solution, along with negligible J–V hysteresis and reproducibility of device performance.